[2/2] f2fs: refactor read path to allow multiple postprocessing steps
diff mbox

Message ID 20180416193147.104555-3-ebiggers@google.com
State Superseded
Headers show

Commit Message

Eric Biggers April 16, 2018, 7:31 p.m. UTC
Currently f2fs's ->readpage() and ->readpages() assume that either the
data undergoes no postprocessing, or decryption only.  But with
fs-verity, there will be an additional authenticity verification step,
and it may be needed either by itself, or combined with decryption.

To support this, store a 'struct bio_post_read_ctx' in ->bi_private
which contains a work struct, a bitmask of postprocessing steps that are
enabled, and an indicator of the current step.  The bio completion
routine, if there was no I/O error, enqueues the first postprocessing
step.  When that completes, it continues to the next step.  Pages that
fail any postprocessing step have PageError set.  Once all steps have
completed, pages without PageError set are set Uptodate, and all pages
are unlocked.

Also replace f2fs_encrypted_file() with a new function
f2fs_post_read_required() in places like direct I/O and garbage
collection that really should be testing whether the file needs special
I/O processing, not whether it is encrypted specifically.

This may also be useful for other future f2fs features such as
compression.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/f2fs/data.c   | 163 +++++++++++++++++++++++++++++++++++------------
 fs/f2fs/f2fs.h   |  12 +++-
 fs/f2fs/file.c   |   4 +-
 fs/f2fs/gc.c     |   6 +-
 fs/f2fs/inline.c |   2 +-
 fs/f2fs/super.c  |   6 ++
 6 files changed, 144 insertions(+), 49 deletions(-)

Comments

Michael Halcrow April 16, 2018, 10:15 p.m. UTC | #1
Given recent talk I've seen on potentially applying file-based
protections in NFS, I think it's worth making some cautionary
observations at this stage.

Moxie's Cryptographic Doom Principle is an approachable take on the
argument that one should verify before performing any other
cryptographic operations.

https://moxie.org/blog/the-cryptographic-doom-principle/

As we consider inline cryptographic engines, this becomes challenging
because encryption is delegated to the block layer, but authenticity
still happens at the file system layer.

That said, the feasibility of applying attacks such as CCA2 against
file sytem content is in question, depending on the adversarial model
for the context in which the file system is integrated.  In
particular, does the model include a MiTM between the kernel and the
storage?

The fs-crypt adversarial model explicitly concerns itself only with a
single point-in-time permanent offline compromise of storage.  I'm not
aware of any real analysis anyone has done when we're instead dealing
with storage that can be arbitrarily modified at arbitrary points in
time.

Is the user concerned about malicious drive controller firmware?  Will
the content be transmitted over an insecure network connection?  Will
the content be otherwise manipulatable by an adversary who can change
to the backing storage?

The other caution relates to compress-then-encrypt.  I refer to the
CRIME and BREACH attacks.

https://en.wikipedia.org/wiki/CRIME

https://en.wikipedia.org/wiki/BREACH

Again, it's context-dependent whether or how attacks like this can
apply to a file system.  We'll need to be explicit about our
expectations as we investigate whether or how to use fs-crypt and
fs-verity capabilities in NFS.  I think this feeds into a discussion
on efficient protection of file system metadata, but I'll defer to
some future thread for that.

On Mon, Apr 16, 2018 at 12:31:47PM -0700, Eric Biggers wrote:
> Currently f2fs's ->readpage() and ->readpages() assume that either the
> data undergoes no postprocessing, or decryption only.  But with
> fs-verity, there will be an additional authenticity verification step,
> and it may be needed either by itself, or combined with decryption.
> 
> To support this, store a 'struct bio_post_read_ctx' in ->bi_private
> which contains a work struct, a bitmask of postprocessing steps that are
> enabled, and an indicator of the current step.  The bio completion
> routine, if there was no I/O error, enqueues the first postprocessing
> step.  When that completes, it continues to the next step.  Pages that
> fail any postprocessing step have PageError set.  Once all steps have
> completed, pages without PageError set are set Uptodate, and all pages
> are unlocked.
> 
> Also replace f2fs_encrypted_file() with a new function
> f2fs_post_read_required() in places like direct I/O and garbage
> collection that really should be testing whether the file needs special
> I/O processing, not whether it is encrypted specifically.
> 
> This may also be useful for other future f2fs features such as
> compression.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  fs/f2fs/data.c   | 163 +++++++++++++++++++++++++++++++++++------------
>  fs/f2fs/f2fs.h   |  12 +++-
>  fs/f2fs/file.c   |   4 +-
>  fs/f2fs/gc.c     |   6 +-
>  fs/f2fs/inline.c |   2 +-
>  fs/f2fs/super.c  |   6 ++
>  6 files changed, 144 insertions(+), 49 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 39225519de1c..ec70de0cd1d5 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -30,6 +30,9 @@
>  #include "trace.h"
>  #include <trace/events/f2fs.h>
>  
> +static struct kmem_cache *bio_post_read_ctx_cache;
> +static mempool_t *bio_post_read_ctx_pool;
> +
>  static bool __is_cp_guaranteed(struct page *page)
>  {
>  	struct address_space *mapping = page->mapping;
> @@ -50,11 +53,77 @@ static bool __is_cp_guaranteed(struct page *page)
>  	return false;
>  }
>  
> -static void f2fs_read_end_io(struct bio *bio)
> +/* postprocessing steps for read bios */
> +enum bio_post_read_step {
> +	STEP_INITIAL = 0,
> +	STEP_DECRYPT,
> +};
> +
> +struct bio_post_read_ctx {
> +	struct bio *bio;
> +	struct work_struct work;
> +	unsigned int cur_step;
> +	unsigned int enabled_steps;

What if enabled_steps has gaps?  E.g., 0x09 will be feasible if
there's compression, encryption, virus signature scanning, and verity.
I'm don't really see how the cur_step logic can be made to be elegant
in that case.

If you start "inital" at 1, then you could collapse these two into
"pending_steps", setting each bit position to 0 after processing.
Just a thought.

> +};
> +
> +static void __read_end_io(struct bio *bio)
>  {
> -	struct bio_vec *bvec;
> +	struct page *page;
> +	struct bio_vec *bv;
>  	int i;
>  
> +	bio_for_each_segment_all(bv, bio, i) {
> +		page = bv->bv_page;
> +
> +		/* PG_error was set if any post_read step failed */
> +		if (bio->bi_status || PageError(page)) {
> +			ClearPageUptodate(page);
> +			SetPageError(page);
> +		} else {
> +			SetPageUptodate(page);
> +		}
> +		unlock_page(page);
> +	}
> +	if (bio->bi_private)
> +		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
> +	bio_put(bio);
> +}
> +
> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> +
> +static void decrypt_work(struct work_struct *work)
> +{
> +	struct bio_post_read_ctx *ctx =
> +		container_of(work, struct bio_post_read_ctx, work);
> +
> +	fscrypt_decrypt_bio(ctx->bio);
> +
> +	bio_post_read_processing(ctx);
> +}
> +
> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> +{
> +	switch (++ctx->cur_step) {
> +	case STEP_DECRYPT:
> +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> +			INIT_WORK(&ctx->work, decrypt_work);
> +			fscrypt_enqueue_decrypt_work(&ctx->work);
> +			return;
> +		}
> +		ctx->cur_step++;
> +		/* fall-through */
> +	default:
> +		__read_end_io(ctx->bio);
> +	}
> +}
> +
> +static bool f2fs_bio_post_read_required(struct bio *bio)
> +{
> +	return bio->bi_private && !bio->bi_status;
> +}
> +
> +static void f2fs_read_end_io(struct bio *bio)
> +{
>  #ifdef CONFIG_F2FS_FAULT_INJECTION
>  	if (time_to_inject(F2FS_P_SB(bio_first_page_all(bio)), FAULT_IO)) {
>  		f2fs_show_injection_info(FAULT_IO);
> @@ -62,28 +131,15 @@ static void f2fs_read_end_io(struct bio *bio)
>  	}
>  #endif
>  
> -	if (f2fs_bio_encrypted(bio)) {
> -		if (bio->bi_status) {
> -			fscrypt_release_ctx(bio->bi_private);
> -		} else {
> -			fscrypt_enqueue_decrypt_bio(bio->bi_private, bio);
> -			return;
> -		}
> -	}
> -
> -	bio_for_each_segment_all(bvec, bio, i) {
> -		struct page *page = bvec->bv_page;
> +	if (f2fs_bio_post_read_required(bio)) {
> +		struct bio_post_read_ctx *ctx = bio->bi_private;
>  
> -		if (!bio->bi_status) {
> -			if (!PageUptodate(page))
> -				SetPageUptodate(page);
> -		} else {
> -			ClearPageUptodate(page);
> -			SetPageError(page);
> -		}
> -		unlock_page(page);
> +		ctx->cur_step = STEP_INITIAL;
> +		bio_post_read_processing(ctx);
> +		return;
>  	}
> -	bio_put(bio);
> +
> +	__read_end_io(bio);
>  }
>  
>  static void f2fs_write_end_io(struct bio *bio)
> @@ -481,29 +537,33 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>  							 unsigned nr_pages)
>  {
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> -	struct fscrypt_ctx *ctx = NULL;
>  	struct bio *bio;
> -
> -	if (f2fs_encrypted_file(inode)) {
> -		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
> -		if (IS_ERR(ctx))
> -			return ERR_CAST(ctx);
> -
> -		/* wait the page to be moved by cleaning */
> -		f2fs_wait_on_block_writeback(sbi, blkaddr);
> -	}
> +	struct bio_post_read_ctx *ctx;
> +	unsigned int post_read_steps = 0;
>  
>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
> -	if (!bio) {
> -		if (ctx)
> -			fscrypt_release_ctx(ctx);
> +	if (!bio)
>  		return ERR_PTR(-ENOMEM);
> -	}
>  	f2fs_target_device(sbi, blkaddr, bio);
>  	bio->bi_end_io = f2fs_read_end_io;
> -	bio->bi_private = ctx;
>  	bio_set_op_attrs(bio, REQ_OP_READ, 0);
>  
> +	if (f2fs_encrypted_file(inode))
> +		post_read_steps |= 1 << STEP_DECRYPT;
> +	if (post_read_steps) {
> +		ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
> +		if (!ctx) {
> +			bio_put(bio);
> +			return ERR_PTR(-ENOMEM);
> +		}
> +		ctx->bio = bio;
> +		ctx->enabled_steps = post_read_steps;
> +		bio->bi_private = ctx;
> +
> +		/* wait the page to be moved by cleaning */
> +		f2fs_wait_on_block_writeback(sbi, blkaddr);
> +	}
> +
>  	return bio;
>  }
>  
> @@ -1525,7 +1585,7 @@ static int encrypt_one_page(struct f2fs_io_info *fio)
>  	if (!f2fs_encrypted_file(inode))
>  		return 0;
>  
> -	/* wait for GCed encrypted page writeback */
> +	/* wait for GCed page writeback via META_MAPPING */
>  	f2fs_wait_on_block_writeback(fio->sbi, fio->old_blkaddr);
>  
>  retry_encrypt:
> @@ -2222,8 +2282,8 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
>  
>  	f2fs_wait_on_page_writeback(page, DATA, false);
>  
> -	/* wait for GCed encrypted page writeback */
> -	if (f2fs_encrypted_file(inode))
> +	/* wait for GCed page writeback via META_MAPPING */
> +	if (f2fs_post_read_required(inode))
>  		f2fs_wait_on_block_writeback(sbi, blkaddr);
>  
>  	if (len == PAGE_SIZE || PageUptodate(page))
> @@ -2555,3 +2615,26 @@ const struct address_space_operations f2fs_dblock_aops = {
>  	.migratepage    = f2fs_migrate_page,
>  #endif
>  };
> +
> +int __init f2fs_init_post_read_processing(void)
> +{
> +	bio_post_read_ctx_cache = KMEM_CACHE(bio_post_read_ctx, 0);
> +	if (!bio_post_read_ctx_cache)
> +		goto fail;
> +	bio_post_read_ctx_pool =
> +		mempool_create_slab_pool(128, bio_post_read_ctx_cache);
> +	if (!bio_post_read_ctx_pool)
> +		goto fail_free_cache;
> +	return 0;
> +
> +fail_free_cache:
> +	kmem_cache_destroy(bio_post_read_ctx_cache);
> +fail:
> +	return -ENOMEM;
> +}
> +
> +void __exit f2fs_destroy_post_read_processing(void)
> +{
> +	mempool_destroy(bio_post_read_ctx_pool);
> +	kmem_cache_destroy(bio_post_read_ctx_cache);
> +}
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1df7f10476d6..ea92c18db624 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2858,6 +2858,8 @@ void destroy_checkpoint_caches(void);
>  /*
>   * data.c
>   */
> +int f2fs_init_post_read_processing(void);
> +void f2fs_destroy_post_read_processing(void);
>  void f2fs_submit_merged_write(struct f2fs_sb_info *sbi, enum page_type type);
>  void f2fs_submit_merged_write_cond(struct f2fs_sb_info *sbi,
>  				struct inode *inode, nid_t ino, pgoff_t idx,
> @@ -3218,9 +3220,13 @@ static inline void f2fs_set_encrypted_inode(struct inode *inode)
>  #endif
>  }
>  
> -static inline bool f2fs_bio_encrypted(struct bio *bio)
> +/*
> + * Returns true if the reads of the inode's data need to undergo some
> + * postprocessing step, like decryption or authenticity verification.
> + */
> +static inline bool f2fs_post_read_required(struct inode *inode)
>  {
> -	return bio->bi_private != NULL;
> +	return f2fs_encrypted_file(inode);
>  }
>  
>  #define F2FS_FEATURE_FUNCS(name, flagname) \
> @@ -3288,7 +3294,7 @@ static inline bool f2fs_may_encrypt(struct inode *inode)
>  
>  static inline bool f2fs_force_buffered_io(struct inode *inode, int rw)
>  {
> -	return (f2fs_encrypted_file(inode) ||
> +	return (f2fs_post_read_required(inode) ||
>  			(rw == WRITE && test_opt(F2FS_I_SB(inode), LFS)) ||
>  			F2FS_I_SB(inode)->s_ndevs);
>  }
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 6b94f19b3fa8..cc08956334a0 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -110,8 +110,8 @@ static int f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>  	/* fill the page */
>  	f2fs_wait_on_page_writeback(page, DATA, false);
>  
> -	/* wait for GCed encrypted page writeback */
> -	if (f2fs_encrypted_file(inode))
> +	/* wait for GCed page writeback via META_MAPPING */
> +	if (f2fs_post_read_required(inode))
>  		f2fs_wait_on_block_writeback(sbi, dn.data_blkaddr);
>  
>  out_sem:
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 9327411fd93b..70418b34c5f6 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -850,8 +850,8 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  			if (IS_ERR(inode) || is_bad_inode(inode))
>  				continue;
>  
> -			/* if encrypted inode, let's go phase 3 */
> -			if (f2fs_encrypted_file(inode)) {
> +			/* if inode uses special I/O path, let's go phase 3 */
> +			if (f2fs_post_read_required(inode)) {
>  				add_gc_inode(gc_list, inode);
>  				continue;
>  			}
> @@ -899,7 +899,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  
>  			start_bidx = start_bidx_of_node(nofs, inode)
>  								+ ofs_in_node;
> -			if (f2fs_encrypted_file(inode))
> +			if (f2fs_post_read_required(inode))
>  				move_data_block(inode, start_bidx, segno, off);
>  			else
>  				move_data_page(inode, start_bidx, gc_type,
> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> index 265da200daa8..767e41d944c6 100644
> --- a/fs/f2fs/inline.c
> +++ b/fs/f2fs/inline.c
> @@ -25,7 +25,7 @@ bool f2fs_may_inline_data(struct inode *inode)
>  	if (i_size_read(inode) > MAX_INLINE_DATA(inode))
>  		return false;
>  
> -	if (f2fs_encrypted_file(inode))
> +	if (f2fs_post_read_required(inode))
>  		return false;
>  
>  	return true;
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 42d564c5ccd0..f31643718c76 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3092,8 +3092,13 @@ static int __init init_f2fs_fs(void)
>  	err = f2fs_create_root_stats();
>  	if (err)
>  		goto free_filesystem;
> +	err = f2fs_init_post_read_processing();
> +	if (err)
> +		goto free_root_stats;
>  	return 0;
>  
> +free_root_stats:
> +	f2fs_destroy_root_stats();
>  free_filesystem:
>  	unregister_filesystem(&f2fs_fs_type);
>  free_shrinker:
> @@ -3116,6 +3121,7 @@ static int __init init_f2fs_fs(void)
>  
>  static void __exit exit_f2fs_fs(void)
>  {
> +	f2fs_destroy_post_read_processing();
>  	f2fs_destroy_root_stats();
>  	unregister_filesystem(&f2fs_fs_type);
>  	unregister_shrinker(&f2fs_shrinker_info);
> -- 
> 2.17.0.484.g0c8726318c-goog
> 
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Chao Yu April 17, 2018, 9:13 a.m. UTC | #2
On 2018/4/17 3:31, Eric Biggers via Linux-f2fs-devel wrote:
> Currently f2fs's ->readpage() and ->readpages() assume that either the
> data undergoes no postprocessing, or decryption only.  But with
> fs-verity, there will be an additional authenticity verification step,
> and it may be needed either by itself, or combined with decryption.
> 
> To support this, store a 'struct bio_post_read_ctx' in ->bi_private
> which contains a work struct, a bitmask of postprocessing steps that are
> enabled, and an indicator of the current step.  The bio completion
> routine, if there was no I/O error, enqueues the first postprocessing
> step.  When that completes, it continues to the next step.  Pages that
> fail any postprocessing step have PageError set.  Once all steps have
> completed, pages without PageError set are set Uptodate, and all pages
> are unlocked.
> 
> Also replace f2fs_encrypted_file() with a new function
> f2fs_post_read_required() in places like direct I/O and garbage
> collection that really should be testing whether the file needs special
> I/O processing, not whether it is encrypted specifically.
> 
> This may also be useful for other future f2fs features such as
> compression.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  fs/f2fs/data.c   | 163 +++++++++++++++++++++++++++++++++++------------
>  fs/f2fs/f2fs.h   |  12 +++-
>  fs/f2fs/file.c   |   4 +-
>  fs/f2fs/gc.c     |   6 +-
>  fs/f2fs/inline.c |   2 +-
>  fs/f2fs/super.c  |   6 ++
>  6 files changed, 144 insertions(+), 49 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 39225519de1c..ec70de0cd1d5 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -30,6 +30,9 @@
>  #include "trace.h"
>  #include <trace/events/f2fs.h>
>  
> +static struct kmem_cache *bio_post_read_ctx_cache;
> +static mempool_t *bio_post_read_ctx_pool;
> +
>  static bool __is_cp_guaranteed(struct page *page)
>  {
>  	struct address_space *mapping = page->mapping;
> @@ -50,11 +53,77 @@ static bool __is_cp_guaranteed(struct page *page)
>  	return false;
>  }
>  
> -static void f2fs_read_end_io(struct bio *bio)
> +/* postprocessing steps for read bios */
> +enum bio_post_read_step {
> +	STEP_INITIAL = 0,
> +	STEP_DECRYPT,
> +};
> +
> +struct bio_post_read_ctx {
> +	struct bio *bio;
> +	struct work_struct work;
> +	unsigned int cur_step;
> +	unsigned int enabled_steps;
> +};
> +
> +static void __read_end_io(struct bio *bio)
>  {
> -	struct bio_vec *bvec;
> +	struct page *page;
> +	struct bio_vec *bv;
>  	int i;
>  
> +	bio_for_each_segment_all(bv, bio, i) {
> +		page = bv->bv_page;
> +
> +		/* PG_error was set if any post_read step failed */
> +		if (bio->bi_status || PageError(page)) {
> +			ClearPageUptodate(page);
> +			SetPageError(page);
> +		} else {
> +			SetPageUptodate(page);
> +		}
> +		unlock_page(page);
> +	}
> +	if (bio->bi_private)
> +		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
> +	bio_put(bio);
> +}
> +
> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> +
> +static void decrypt_work(struct work_struct *work)
> +{
> +	struct bio_post_read_ctx *ctx =
> +		container_of(work, struct bio_post_read_ctx, work);
> +
> +	fscrypt_decrypt_bio(ctx->bio);
> +
> +	bio_post_read_processing(ctx);
> +}
> +
> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> +{
> +	switch (++ctx->cur_step) {
> +	case STEP_DECRYPT:
> +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> +			INIT_WORK(&ctx->work, decrypt_work);
> +			fscrypt_enqueue_decrypt_work(&ctx->work);
> +			return;
> +		}
> +		ctx->cur_step++;
> +		/* fall-through */
> +	default:
> +		__read_end_io(ctx->bio);
> +	}

How about introducing __bio_post_read_processing()

switch (step) {
case STEP_DECRYPT:
	...
	break;
case STEP_COMPRESS:
	...
	break;
case STEP_GENERIC:
	__read_end_io;
	break;
...
}

Then we can customize flexible read processes like:

bio_post_read_processing()
{
	if (encrypt_enabled)
		__bio_post_read_processing(, STEP_DECRYPT);
	if (compress_enabled)
		__bio_post_read_processing(, STEP_COMPRESS);
	__bio_post_read_processing(, STEP_GENERIC);
}

Or other flow.

> +}
> +
> +static bool f2fs_bio_post_read_required(struct bio *bio)
> +{
> +	return bio->bi_private && !bio->bi_status;
> +}
> +
> +static void f2fs_read_end_io(struct bio *bio)
> +{
>  #ifdef CONFIG_F2FS_FAULT_INJECTION
>  	if (time_to_inject(F2FS_P_SB(bio_first_page_all(bio)), FAULT_IO)) {
>  		f2fs_show_injection_info(FAULT_IO);
> @@ -62,28 +131,15 @@ static void f2fs_read_end_io(struct bio *bio)
>  	}
>  #endif
>  
> -	if (f2fs_bio_encrypted(bio)) {
> -		if (bio->bi_status) {
> -			fscrypt_release_ctx(bio->bi_private);
> -		} else {
> -			fscrypt_enqueue_decrypt_bio(bio->bi_private, bio);
> -			return;
> -		}
> -	}
> -
> -	bio_for_each_segment_all(bvec, bio, i) {
> -		struct page *page = bvec->bv_page;
> +	if (f2fs_bio_post_read_required(bio)) {
> +		struct bio_post_read_ctx *ctx = bio->bi_private;
>  
> -		if (!bio->bi_status) {
> -			if (!PageUptodate(page))
> -				SetPageUptodate(page);
> -		} else {
> -			ClearPageUptodate(page);
> -			SetPageError(page);
> -		}
> -		unlock_page(page);
> +		ctx->cur_step = STEP_INITIAL;
> +		bio_post_read_processing(ctx);
> +		return;
>  	}
> -	bio_put(bio);
> +
> +	__read_end_io(bio);
>  }
>  
>  static void f2fs_write_end_io(struct bio *bio)
> @@ -481,29 +537,33 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>  							 unsigned nr_pages)
>  {
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> -	struct fscrypt_ctx *ctx = NULL;
>  	struct bio *bio;
> -
> -	if (f2fs_encrypted_file(inode)) {
> -		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
> -		if (IS_ERR(ctx))
> -			return ERR_CAST(ctx);
> -
> -		/* wait the page to be moved by cleaning */
> -		f2fs_wait_on_block_writeback(sbi, blkaddr);
> -	}
> +	struct bio_post_read_ctx *ctx;
> +	unsigned int post_read_steps = 0;
>  
>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
> -	if (!bio) {
> -		if (ctx)
> -			fscrypt_release_ctx(ctx);
> +	if (!bio)
>  		return ERR_PTR(-ENOMEM);
> -	}
>  	f2fs_target_device(sbi, blkaddr, bio);
>  	bio->bi_end_io = f2fs_read_end_io;
> -	bio->bi_private = ctx;

bio->bi_private = NULL;

>  	bio_set_op_attrs(bio, REQ_OP_READ, 0);
>  
> +	if (f2fs_encrypted_file(inode))
> +		post_read_steps |= 1 << STEP_DECRYPT;
> +	if (post_read_steps) {
> +		ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
> +		if (!ctx) {
> +			bio_put(bio);
> +			return ERR_PTR(-ENOMEM);
> +		}
> +		ctx->bio = bio;
> +		ctx->enabled_steps = post_read_steps;
> +		bio->bi_private = ctx;
> +
> +		/* wait the page to be moved by cleaning */
> +		f2fs_wait_on_block_writeback(sbi, blkaddr);
> +	}
> +
>  	return bio;
>  }
>  
> @@ -1525,7 +1585,7 @@ static int encrypt_one_page(struct f2fs_io_info *fio)
>  	if (!f2fs_encrypted_file(inode))
>  		return 0;
>  
> -	/* wait for GCed encrypted page writeback */
> +	/* wait for GCed page writeback via META_MAPPING */
>  	f2fs_wait_on_block_writeback(fio->sbi, fio->old_blkaddr);
>  
>  retry_encrypt:
> @@ -2222,8 +2282,8 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
>  
>  	f2fs_wait_on_page_writeback(page, DATA, false);
>  
> -	/* wait for GCed encrypted page writeback */
> -	if (f2fs_encrypted_file(inode))
> +	/* wait for GCed page writeback via META_MAPPING */
> +	if (f2fs_post_read_required(inode))
>  		f2fs_wait_on_block_writeback(sbi, blkaddr);
>  
>  	if (len == PAGE_SIZE || PageUptodate(page))
> @@ -2555,3 +2615,26 @@ const struct address_space_operations f2fs_dblock_aops = {
>  	.migratepage    = f2fs_migrate_page,
>  #endif
>  };
> +
> +int __init f2fs_init_post_read_processing(void)
> +{
> +	bio_post_read_ctx_cache = KMEM_CACHE(bio_post_read_ctx, 0);
> +	if (!bio_post_read_ctx_cache)
> +		goto fail;
> +	bio_post_read_ctx_pool =
> +		mempool_create_slab_pool(128, bio_post_read_ctx_cache);

#define MAX_POST_READ_CACHE_SIZE	128

Thanks,

> +	if (!bio_post_read_ctx_pool)
> +		goto fail_free_cache;
> +	return 0;
> +
> +fail_free_cache:
> +	kmem_cache_destroy(bio_post_read_ctx_cache);
> +fail:
> +	return -ENOMEM;
> +}
> +
> +void __exit f2fs_destroy_post_read_processing(void)
> +{
> +	mempool_destroy(bio_post_read_ctx_pool);
> +	kmem_cache_destroy(bio_post_read_ctx_cache);
> +}
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1df7f10476d6..ea92c18db624 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2858,6 +2858,8 @@ void destroy_checkpoint_caches(void);
>  /*
>   * data.c
>   */
> +int f2fs_init_post_read_processing(void);
> +void f2fs_destroy_post_read_processing(void);
>  void f2fs_submit_merged_write(struct f2fs_sb_info *sbi, enum page_type type);
>  void f2fs_submit_merged_write_cond(struct f2fs_sb_info *sbi,
>  				struct inode *inode, nid_t ino, pgoff_t idx,
> @@ -3218,9 +3220,13 @@ static inline void f2fs_set_encrypted_inode(struct inode *inode)
>  #endif
>  }
>  
> -static inline bool f2fs_bio_encrypted(struct bio *bio)
> +/*
> + * Returns true if the reads of the inode's data need to undergo some
> + * postprocessing step, like decryption or authenticity verification.
> + */
> +static inline bool f2fs_post_read_required(struct inode *inode)
>  {
> -	return bio->bi_private != NULL;
> +	return f2fs_encrypted_file(inode);
>  }
>  
>  #define F2FS_FEATURE_FUNCS(name, flagname) \
> @@ -3288,7 +3294,7 @@ static inline bool f2fs_may_encrypt(struct inode *inode)
>  
>  static inline bool f2fs_force_buffered_io(struct inode *inode, int rw)
>  {
> -	return (f2fs_encrypted_file(inode) ||
> +	return (f2fs_post_read_required(inode) ||
>  			(rw == WRITE && test_opt(F2FS_I_SB(inode), LFS)) ||
>  			F2FS_I_SB(inode)->s_ndevs);
>  }
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 6b94f19b3fa8..cc08956334a0 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -110,8 +110,8 @@ static int f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>  	/* fill the page */
>  	f2fs_wait_on_page_writeback(page, DATA, false);
>  
> -	/* wait for GCed encrypted page writeback */
> -	if (f2fs_encrypted_file(inode))
> +	/* wait for GCed page writeback via META_MAPPING */
> +	if (f2fs_post_read_required(inode))
>  		f2fs_wait_on_block_writeback(sbi, dn.data_blkaddr);
>  
>  out_sem:
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 9327411fd93b..70418b34c5f6 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -850,8 +850,8 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  			if (IS_ERR(inode) || is_bad_inode(inode))
>  				continue;
>  
> -			/* if encrypted inode, let's go phase 3 */
> -			if (f2fs_encrypted_file(inode)) {
> +			/* if inode uses special I/O path, let's go phase 3 */
> +			if (f2fs_post_read_required(inode)) {
>  				add_gc_inode(gc_list, inode);
>  				continue;
>  			}
> @@ -899,7 +899,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  
>  			start_bidx = start_bidx_of_node(nofs, inode)
>  								+ ofs_in_node;
> -			if (f2fs_encrypted_file(inode))
> +			if (f2fs_post_read_required(inode))
>  				move_data_block(inode, start_bidx, segno, off);
>  			else
>  				move_data_page(inode, start_bidx, gc_type,
> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> index 265da200daa8..767e41d944c6 100644
> --- a/fs/f2fs/inline.c
> +++ b/fs/f2fs/inline.c
> @@ -25,7 +25,7 @@ bool f2fs_may_inline_data(struct inode *inode)
>  	if (i_size_read(inode) > MAX_INLINE_DATA(inode))
>  		return false;
>  
> -	if (f2fs_encrypted_file(inode))
> +	if (f2fs_post_read_required(inode))
>  		return false;
>  
>  	return true;
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 42d564c5ccd0..f31643718c76 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3092,8 +3092,13 @@ static int __init init_f2fs_fs(void)
>  	err = f2fs_create_root_stats();
>  	if (err)
>  		goto free_filesystem;
> +	err = f2fs_init_post_read_processing();
> +	if (err)
> +		goto free_root_stats;
>  	return 0;
>  
> +free_root_stats:
> +	f2fs_destroy_root_stats();
>  free_filesystem:
>  	unregister_filesystem(&f2fs_fs_type);
>  free_shrinker:
> @@ -3116,6 +3121,7 @@ static int __init init_f2fs_fs(void)
>  
>  static void __exit exit_f2fs_fs(void)
>  {
> +	f2fs_destroy_post_read_processing();
>  	f2fs_destroy_root_stats();
>  	unregister_filesystem(&f2fs_fs_type);
>  	unregister_shrinker(&f2fs_shrinker_info);
> 

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Eric Biggers April 17, 2018, 5:31 p.m. UTC | #3
Hi Michael,

On Mon, Apr 16, 2018 at 03:15:42PM -0700, Michael Halcrow wrote:
> Given recent talk I've seen on potentially applying file-based
> protections in NFS, I think it's worth making some cautionary
> observations at this stage.
> 
> Moxie's Cryptographic Doom Principle is an approachable take on the
> argument that one should verify before performing any other
> cryptographic operations.
> 
> https://moxie.org/blog/the-cryptographic-doom-principle/
> 
> As we consider inline cryptographic engines, this becomes challenging
> because encryption is delegated to the block layer, but authenticity
> still happens at the file system layer.
> 
> That said, the feasibility of applying attacks such as CCA2 against
> file sytem content is in question, depending on the adversarial model
> for the context in which the file system is integrated.  In
> particular, does the model include a MiTM between the kernel and the
> storage?
> 
> The fs-crypt adversarial model explicitly concerns itself only with a
> single point-in-time permanent offline compromise of storage.  I'm not
> aware of any real analysis anyone has done when we're instead dealing
> with storage that can be arbitrarily modified at arbitrary points in
> time.

I feel that your concerns are a bit off-topic for what this patch actually does,
but yes I don't think data confidentiality with fscrypt is guaranteed when an
attacker controls the disk.  And actually, fs-verity won't really change this
because fs-verity will only protect the file contents of immutable files.  It
won't protect filesystem metadata, or of mutable files.  In other words, most
files the user cares about the confidentiality of won't be protected by
fs-verity anyway.

Also, fs-verity will need to authenticate the plaintext (i.e. STEP_VERITY will
come after STEP_DECRYPT) because it may need to authenticate some well known
file, like an APK file that was signed by a certain entity.  But, when combined
with fscrypt, by the design of fscrypt on each device the file will be encrypted
with a unique key, resulting in a unique ciphertext.  The ciphertext is also not
visible to userspace currently so it would not be possible for a userspace tool
to generate the fs-verity metadata.

> 
> Is the user concerned about malicious drive controller firmware?  Will
> the content be transmitted over an insecure network connection?  Will
> the content be otherwise manipulatable by an adversary who can change
> to the backing storage?
> 
> The other caution relates to compress-then-encrypt.  I refer to the
> CRIME and BREACH attacks.
> 
> https://en.wikipedia.org/wiki/CRIME
> 
> https://en.wikipedia.org/wiki/BREACH
> 
> Again, it's context-dependent whether or how attacks like this can
> apply to a file system.  We'll need to be explicit about our
> expectations as we investigate whether or how to use fs-crypt and
> fs-verity capabilities in NFS.  I think this feeds into a discussion
> on efficient protection of file system metadata, but I'll defer to
> some future thread for that.

To be clear, neither f2fs nor NFS actually supports compression yet.  At least
for f2fs it's just a feature that some people want, and *might* be implemented
in the future.  Note that some people will want just compression and others will
want just encryption, so having both features available won't mean that everyone
will use both.  It will need to be discussed at that time how risky combining
them really is and whether it should be allowed or not -- or perhaps allowed but
with a warning explaining the risk.

> >  
> > -static void f2fs_read_end_io(struct bio *bio)
> > +/* postprocessing steps for read bios */
> > +enum bio_post_read_step {
> > +	STEP_INITIAL = 0,
> > +	STEP_DECRYPT,
> > +};
> > +
> > +struct bio_post_read_ctx {
> > +	struct bio *bio;
> > +	struct work_struct work;
> > +	unsigned int cur_step;
> > +	unsigned int enabled_steps;
> 
> What if enabled_steps has gaps?  E.g., 0x09 will be feasible if
> there's compression, encryption, virus signature scanning, and verity.
> I'm don't really see how the cur_step logic can be made to be elegant
> in that case.
> 
> If you start "inital" at 1, then you could collapse these two into
> "pending_steps", setting each bit position to 0 after processing.
> Just a thought.
> 

It will actually work fine.  In bio_post_read_processing(), we'll just fall
through and increment 'cur_step' until we get to the next step.  When there are
many steps we certainly could optimize it to use a bitmask and ffs() to
efficiently find the next step, but for now we are talking about maybe 1-3 steps
only, so I went with what seemed simplest.

Thanks,

Eric
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Eric Biggers April 17, 2018, 5:42 p.m. UTC | #4
Hi Chao,

On Tue, Apr 17, 2018 at 05:13:12PM +0800, Chao Yu wrote:
> > +
> > +static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> > +
> > +static void decrypt_work(struct work_struct *work)
> > +{
> > +	struct bio_post_read_ctx *ctx =
> > +		container_of(work, struct bio_post_read_ctx, work);
> > +
> > +	fscrypt_decrypt_bio(ctx->bio);
> > +
> > +	bio_post_read_processing(ctx);
> > +}
> > +
> > +static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> > +{
> > +	switch (++ctx->cur_step) {
> > +	case STEP_DECRYPT:
> > +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> > +			INIT_WORK(&ctx->work, decrypt_work);
> > +			fscrypt_enqueue_decrypt_work(&ctx->work);
> > +			return;
> > +		}
> > +		ctx->cur_step++;
> > +		/* fall-through */
> > +	default:
> > +		__read_end_io(ctx->bio);
> > +	}
> 
> How about introducing __bio_post_read_processing()
> 
> switch (step) {
> case STEP_DECRYPT:
> 	...
> 	break;
> case STEP_COMPRESS:
> 	...
> 	break;
> case STEP_GENERIC:
> 	__read_end_io;
> 	break;
> ...
> }
> 
> Then we can customize flexible read processes like:
> 
> bio_post_read_processing()
> {
> 	if (encrypt_enabled)
> 		__bio_post_read_processing(, STEP_DECRYPT);
> 	if (compress_enabled)
> 		__bio_post_read_processing(, STEP_COMPRESS);
> 	__bio_post_read_processing(, STEP_GENERIC);
> }
> 
> Or other flow.

If I understand correctly, you're suggesting that all the steps be done in a
single workqueue item?  The problem with that is that the verity work will
require I/O to the file to read hashes, which may need STEP_DECRYPT.  Hence,
decryption and verity will need separate workqueues.

> > @@ -481,29 +537,33 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
> >  							 unsigned nr_pages)
> >  {
> >  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > -	struct fscrypt_ctx *ctx = NULL;
> >  	struct bio *bio;
> > -
> > -	if (f2fs_encrypted_file(inode)) {
> > -		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
> > -		if (IS_ERR(ctx))
> > -			return ERR_CAST(ctx);
> > -
> > -		/* wait the page to be moved by cleaning */
> > -		f2fs_wait_on_block_writeback(sbi, blkaddr);
> > -	}
> > +	struct bio_post_read_ctx *ctx;
> > +	unsigned int post_read_steps = 0;
> >  
> >  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
> > -	if (!bio) {
> > -		if (ctx)
> > -			fscrypt_release_ctx(ctx);
> > +	if (!bio)
> >  		return ERR_PTR(-ENOMEM);
> > -	}
> >  	f2fs_target_device(sbi, blkaddr, bio);
> >  	bio->bi_end_io = f2fs_read_end_io;
> > -	bio->bi_private = ctx;
> 
> bio->bi_private = NULL;
> 

I don't see why.  ->bi_private is NULL by default.

> > +	bio_post_read_ctx_pool =
> > +		mempool_create_slab_pool(128, bio_post_read_ctx_cache);
> 
> #define MAX_POST_READ_CACHE_SIZE	128
> 

Yes, that makes sense.

- Eric
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Chao Yu April 18, 2018, 6:27 a.m. UTC | #5
Hi Eric,

On 2018/4/18 1:42, Eric Biggers wrote:
> Hi Chao,
> 
> On Tue, Apr 17, 2018 at 05:13:12PM +0800, Chao Yu wrote:
>>> +
>>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
>>> +
>>> +static void decrypt_work(struct work_struct *work)
>>> +{
>>> +	struct bio_post_read_ctx *ctx =
>>> +		container_of(work, struct bio_post_read_ctx, work);
>>> +
>>> +	fscrypt_decrypt_bio(ctx->bio);
>>> +
>>> +	bio_post_read_processing(ctx);
>>> +}
>>> +
>>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
>>> +{
>>> +	switch (++ctx->cur_step) {
>>> +	case STEP_DECRYPT:
>>> +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
>>> +			INIT_WORK(&ctx->work, decrypt_work);
>>> +			fscrypt_enqueue_decrypt_work(&ctx->work);
>>> +			return;
>>> +		}
>>> +		ctx->cur_step++;
>>> +		/* fall-through */
>>> +	default:
>>> +		__read_end_io(ctx->bio);
>>> +	}
>>
>> How about introducing __bio_post_read_processing()
>>
>> switch (step) {
>> case STEP_DECRYPT:
>> 	...
>> 	break;
>> case STEP_COMPRESS:
>> 	...
>> 	break;
>> case STEP_GENERIC:
>> 	__read_end_io;
>> 	break;
>> ...
>> }
>>
>> Then we can customize flexible read processes like:
>>
>> bio_post_read_processing()
>> {
>> 	if (encrypt_enabled)
>> 		__bio_post_read_processing(, STEP_DECRYPT);
>> 	if (compress_enabled)
>> 		__bio_post_read_processing(, STEP_COMPRESS);
>> 	__bio_post_read_processing(, STEP_GENERIC);
>> }
>>
>> Or other flow.
> 
> If I understand correctly, you're suggesting that all the steps be done in a
> single workqueue item?  The problem with that is that the verity work will

Yup,

> require I/O to the file to read hashes, which may need STEP_DECRYPT.  Hence,
> decryption and verity will need separate workqueues.

For decryption and verity, the needs separated data, I agree that we can not
merge the work into one workqueue.

As you mentioned in commit message, it can be used by compression later, so I
just thought that for decryption and decompression, maybe we can do those work
sequentially in one workqueue?

> 
>>> @@ -481,29 +537,33 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>>>  							 unsigned nr_pages)
>>>  {
>>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>> -	struct fscrypt_ctx *ctx = NULL;
>>>  	struct bio *bio;
>>> -
>>> -	if (f2fs_encrypted_file(inode)) {
>>> -		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
>>> -		if (IS_ERR(ctx))
>>> -			return ERR_CAST(ctx);
>>> -
>>> -		/* wait the page to be moved by cleaning */
>>> -		f2fs_wait_on_block_writeback(sbi, blkaddr);
>>> -	}
>>> +	struct bio_post_read_ctx *ctx;
>>> +	unsigned int post_read_steps = 0;
>>>  
>>>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
>>> -	if (!bio) {
>>> -		if (ctx)
>>> -			fscrypt_release_ctx(ctx);
>>> +	if (!bio)
>>>  		return ERR_PTR(-ENOMEM);
>>> -	}
>>>  	f2fs_target_device(sbi, blkaddr, bio);
>>>  	bio->bi_end_io = f2fs_read_end_io;
>>> -	bio->bi_private = ctx;
>>
>> bio->bi_private = NULL;
>>
> 
> I don't see why.  ->bi_private is NULL by default.

As we will check bi_private in read_end_io anyway, if it is not NULL, we will
parse it as an ctx, am I missing something?

Thanks,

> 
>>> +	bio_post_read_ctx_pool =
>>> +		mempool_create_slab_pool(128, bio_post_read_ctx_cache);
>>
>> #define MAX_POST_READ_CACHE_SIZE	128
>>
> 
> Yes, that makes sense.
> 
> - Eric
> 
> .
> 

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Eric Biggers April 18, 2018, 5:18 p.m. UTC | #6
Hi Chao,

On Wed, Apr 18, 2018 at 02:27:32PM +0800, Chao Yu wrote:
> Hi Eric,
> 
> On 2018/4/18 1:42, Eric Biggers wrote:
> > Hi Chao,
> > 
> > On Tue, Apr 17, 2018 at 05:13:12PM +0800, Chao Yu wrote:
> >>> +
> >>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> >>> +
> >>> +static void decrypt_work(struct work_struct *work)
> >>> +{
> >>> +	struct bio_post_read_ctx *ctx =
> >>> +		container_of(work, struct bio_post_read_ctx, work);
> >>> +
> >>> +	fscrypt_decrypt_bio(ctx->bio);
> >>> +
> >>> +	bio_post_read_processing(ctx);
> >>> +}
> >>> +
> >>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> >>> +{
> >>> +	switch (++ctx->cur_step) {
> >>> +	case STEP_DECRYPT:
> >>> +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> >>> +			INIT_WORK(&ctx->work, decrypt_work);
> >>> +			fscrypt_enqueue_decrypt_work(&ctx->work);
> >>> +			return;
> >>> +		}
> >>> +		ctx->cur_step++;
> >>> +		/* fall-through */
> >>> +	default:
> >>> +		__read_end_io(ctx->bio);
> >>> +	}
> >>
> >> How about introducing __bio_post_read_processing()
> >>
> >> switch (step) {
> >> case STEP_DECRYPT:
> >> 	...
> >> 	break;
> >> case STEP_COMPRESS:
> >> 	...
> >> 	break;
> >> case STEP_GENERIC:
> >> 	__read_end_io;
> >> 	break;
> >> ...
> >> }
> >>
> >> Then we can customize flexible read processes like:
> >>
> >> bio_post_read_processing()
> >> {
> >> 	if (encrypt_enabled)
> >> 		__bio_post_read_processing(, STEP_DECRYPT);
> >> 	if (compress_enabled)
> >> 		__bio_post_read_processing(, STEP_COMPRESS);
> >> 	__bio_post_read_processing(, STEP_GENERIC);
> >> }
> >>
> >> Or other flow.
> > 
> > If I understand correctly, you're suggesting that all the steps be done in a
> > single workqueue item?  The problem with that is that the verity work will
> 
> Yup,
> 
> > require I/O to the file to read hashes, which may need STEP_DECRYPT.  Hence,
> > decryption and verity will need separate workqueues.
> 
> For decryption and verity, the needs separated data, I agree that we can not
> merge the work into one workqueue.
> 
> As you mentioned in commit message, it can be used by compression later, so I
> just thought that for decryption and decompression, maybe we can do those work
> sequentially in one workqueue?
> 

Sure.  I'm not sure what you're asking me to do, though, since f2fs compression
doesn't exist yet.  If/when there are multiple steps that can be combined, then
bio_post_read_processing() can be updated to schedule them together.

> > 
> >>> @@ -481,29 +537,33 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
> >>>  							 unsigned nr_pages)
> >>>  {
> >>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>> -	struct fscrypt_ctx *ctx = NULL;
> >>>  	struct bio *bio;
> >>> -
> >>> -	if (f2fs_encrypted_file(inode)) {
> >>> -		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
> >>> -		if (IS_ERR(ctx))
> >>> -			return ERR_CAST(ctx);
> >>> -
> >>> -		/* wait the page to be moved by cleaning */
> >>> -		f2fs_wait_on_block_writeback(sbi, blkaddr);
> >>> -	}
> >>> +	struct bio_post_read_ctx *ctx;
> >>> +	unsigned int post_read_steps = 0;
> >>>  
> >>>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
> >>> -	if (!bio) {
> >>> -		if (ctx)
> >>> -			fscrypt_release_ctx(ctx);
> >>> +	if (!bio)
> >>>  		return ERR_PTR(-ENOMEM);
> >>> -	}
> >>>  	f2fs_target_device(sbi, blkaddr, bio);
> >>>  	bio->bi_end_io = f2fs_read_end_io;
> >>> -	bio->bi_private = ctx;
> >>
> >> bio->bi_private = NULL;
> >>
> > 
> > I don't see why.  ->bi_private is NULL by default.
> 
> As we will check bi_private in read_end_io anyway, if it is not NULL, we will
> parse it as an ctx, am I missing something?
> 

We're allocating a new bio.  New bios have NULL ->bi_private.

> Thanks,
> 
> > 
> >>> +	bio_post_read_ctx_pool =
> >>> +		mempool_create_slab_pool(128, bio_post_read_ctx_cache);
> >>
> >> #define MAX_POST_READ_CACHE_SIZE	128
> >>
> > 
> > Yes, that makes sense.
> > 

Actually it's the number of contexts preallocated in the mempool, so I'm going
to call it NUM_PREALLOC_POST_READ_CTXS.  It's similar to
'num_prealloc_crypto_ctxs' in fs/crypto/crypto.c.

Eric
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Jaegeuk Kim April 18, 2018, 5:37 p.m. UTC | #7
On 04/18, Eric Biggers wrote:
> Hi Chao,
> 
> On Wed, Apr 18, 2018 at 02:27:32PM +0800, Chao Yu wrote:
> > Hi Eric,
> > 
> > On 2018/4/18 1:42, Eric Biggers wrote:
> > > Hi Chao,
> > > 
> > > On Tue, Apr 17, 2018 at 05:13:12PM +0800, Chao Yu wrote:
> > >>> +
> > >>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> > >>> +
> > >>> +static void decrypt_work(struct work_struct *work)
> > >>> +{
> > >>> +	struct bio_post_read_ctx *ctx =
> > >>> +		container_of(work, struct bio_post_read_ctx, work);
> > >>> +
> > >>> +	fscrypt_decrypt_bio(ctx->bio);
> > >>> +
> > >>> +	bio_post_read_processing(ctx);
> > >>> +}
> > >>> +
> > >>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> > >>> +{
> > >>> +	switch (++ctx->cur_step) {
> > >>> +	case STEP_DECRYPT:
> > >>> +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> > >>> +			INIT_WORK(&ctx->work, decrypt_work);
> > >>> +			fscrypt_enqueue_decrypt_work(&ctx->work);
> > >>> +			return;
> > >>> +		}
> > >>> +		ctx->cur_step++;
> > >>> +		/* fall-through */
> > >>> +	default:
> > >>> +		__read_end_io(ctx->bio);
> > >>> +	}
> > >>
> > >> How about introducing __bio_post_read_processing()
> > >>
> > >> switch (step) {
> > >> case STEP_DECRYPT:
> > >> 	...
> > >> 	break;
> > >> case STEP_COMPRESS:
> > >> 	...
> > >> 	break;
> > >> case STEP_GENERIC:
> > >> 	__read_end_io;
> > >> 	break;
> > >> ...
> > >> }
> > >>
> > >> Then we can customize flexible read processes like:
> > >>
> > >> bio_post_read_processing()
> > >> {
> > >> 	if (encrypt_enabled)
> > >> 		__bio_post_read_processing(, STEP_DECRYPT);
> > >> 	if (compress_enabled)
> > >> 		__bio_post_read_processing(, STEP_COMPRESS);
> > >> 	__bio_post_read_processing(, STEP_GENERIC);
> > >> }
> > >>
> > >> Or other flow.
> > > 
> > > If I understand correctly, you're suggesting that all the steps be done in a
> > > single workqueue item?  The problem with that is that the verity work will
> > 
> > Yup,
> > 
> > > require I/O to the file to read hashes, which may need STEP_DECRYPT.  Hence,
> > > decryption and verity will need separate workqueues.
> > 
> > For decryption and verity, the needs separated data, I agree that we can not
> > merge the work into one workqueue.
> > 
> > As you mentioned in commit message, it can be used by compression later, so I
> > just thought that for decryption and decompression, maybe we can do those work
> > sequentially in one workqueue?
> > 
> 
> Sure.  I'm not sure what you're asking me to do, though, since f2fs compression
> doesn't exist yet.  If/when there are multiple steps that can be combined, then
> bio_post_read_processing() can be updated to schedule them together.

Indeed, we may need to consolidate many workqueues into one later, not at this
time, IMO.

> 
> > > 
> > >>> @@ -481,29 +537,33 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
> > >>>  							 unsigned nr_pages)
> > >>>  {
> > >>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > >>> -	struct fscrypt_ctx *ctx = NULL;
> > >>>  	struct bio *bio;
> > >>> -
> > >>> -	if (f2fs_encrypted_file(inode)) {
> > >>> -		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
> > >>> -		if (IS_ERR(ctx))
> > >>> -			return ERR_CAST(ctx);
> > >>> -
> > >>> -		/* wait the page to be moved by cleaning */
> > >>> -		f2fs_wait_on_block_writeback(sbi, blkaddr);
> > >>> -	}
> > >>> +	struct bio_post_read_ctx *ctx;
> > >>> +	unsigned int post_read_steps = 0;
> > >>>  
> > >>>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
> > >>> -	if (!bio) {
> > >>> -		if (ctx)
> > >>> -			fscrypt_release_ctx(ctx);
> > >>> +	if (!bio)
> > >>>  		return ERR_PTR(-ENOMEM);
> > >>> -	}
> > >>>  	f2fs_target_device(sbi, blkaddr, bio);
> > >>>  	bio->bi_end_io = f2fs_read_end_io;
> > >>> -	bio->bi_private = ctx;
> > >>
> > >> bio->bi_private = NULL;
> > >>
> > > 
> > > I don't see why.  ->bi_private is NULL by default.
> > 
> > As we will check bi_private in read_end_io anyway, if it is not NULL, we will
> > parse it as an ctx, am I missing something?
> > 
> 
> We're allocating a new bio.  New bios have NULL ->bi_private.

+1.

bio_init() does memset();

> 
> > Thanks,
> > 
> > > 
> > >>> +	bio_post_read_ctx_pool =
> > >>> +		mempool_create_slab_pool(128, bio_post_read_ctx_cache);
> > >>
> > >> #define MAX_POST_READ_CACHE_SIZE	128
> > >>
> > > 
> > > Yes, that makes sense.
> > > 
> 
> Actually it's the number of contexts preallocated in the mempool, so I'm going
> to call it NUM_PREALLOC_POST_READ_CTXS.  It's similar to
> 'num_prealloc_crypto_ctxs' in fs/crypto/crypto.c.

Could you please post v2?

Chao,

Let me know, if you have other concern on this. Otherwise, let me queue v2
firmly.

Thanks,

> 
> Eric
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Chao Yu April 19, 2018, 2:41 p.m. UTC | #8
Hi Eric and Jaegeuk,

On 2018/4/19 1:18, Eric Biggers via Linux-f2fs-devel wrote:
> Hi Chao,
> 
> On Wed, Apr 18, 2018 at 02:27:32PM +0800, Chao Yu wrote:
>> Hi Eric,
>>
>> On 2018/4/18 1:42, Eric Biggers wrote:
>>> Hi Chao,
>>>
>>> On Tue, Apr 17, 2018 at 05:13:12PM +0800, Chao Yu wrote:
>>>>> +
>>>>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
>>>>> +
>>>>> +static void decrypt_work(struct work_struct *work)
>>>>> +{
>>>>> +	struct bio_post_read_ctx *ctx =
>>>>> +		container_of(work, struct bio_post_read_ctx, work);
>>>>> +
>>>>> +	fscrypt_decrypt_bio(ctx->bio);
>>>>> +
>>>>> +	bio_post_read_processing(ctx);
>>>>> +}
>>>>> +
>>>>> +static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
>>>>> +{
>>>>> +	switch (++ctx->cur_step) {
>>>>> +	case STEP_DECRYPT:
>>>>> +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
>>>>> +			INIT_WORK(&ctx->work, decrypt_work);
>>>>> +			fscrypt_enqueue_decrypt_work(&ctx->work);
>>>>> +			return;
>>>>> +		}
>>>>> +		ctx->cur_step++;
>>>>> +		/* fall-through */
>>>>> +	default:
>>>>> +		__read_end_io(ctx->bio);
>>>>> +	}
>>>>
>>>> How about introducing __bio_post_read_processing()
>>>>
>>>> switch (step) {
>>>> case STEP_DECRYPT:
>>>> 	...
>>>> 	break;
>>>> case STEP_COMPRESS:
>>>> 	...
>>>> 	break;
>>>> case STEP_GENERIC:
>>>> 	__read_end_io;
>>>> 	break;
>>>> ...
>>>> }
>>>>
>>>> Then we can customize flexible read processes like:
>>>>
>>>> bio_post_read_processing()
>>>> {
>>>> 	if (encrypt_enabled)
>>>> 		__bio_post_read_processing(, STEP_DECRYPT);
>>>> 	if (compress_enabled)
>>>> 		__bio_post_read_processing(, STEP_COMPRESS);
>>>> 	__bio_post_read_processing(, STEP_GENERIC);
>>>> }
>>>>
>>>> Or other flow.
>>>
>>> If I understand correctly, you're suggesting that all the steps be done in a
>>> single workqueue item?  The problem with that is that the verity work will
>>
>> Yup,
>>
>>> require I/O to the file to read hashes, which may need STEP_DECRYPT.  Hence,
>>> decryption and verity will need separate workqueues.
>>
>> For decryption and verity, the needs separated data, I agree that we can not
>> merge the work into one workqueue.
>>
>> As you mentioned in commit message, it can be used by compression later, so I
>> just thought that for decryption and decompression, maybe we can do those work
>> sequentially in one workqueue?
>>
> 
> Sure.  I'm not sure what you're asking me to do, though, since f2fs compression

Oh, I just want to make codes be more scalability, once we want to add more
features which will need a background task, we can easily add one more case
handler in the function to support it.

> doesn't exist yet.  If/when there are multiple steps that can be combined, then
> bio_post_read_processing() can be updated to schedule them together.

Alright, please go ahead with original design.

> 
>>>
>>>>> @@ -481,29 +537,33 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>>>>>  							 unsigned nr_pages)
>>>>>  {
>>>>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>>> -	struct fscrypt_ctx *ctx = NULL;
>>>>>  	struct bio *bio;
>>>>> -
>>>>> -	if (f2fs_encrypted_file(inode)) {
>>>>> -		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
>>>>> -		if (IS_ERR(ctx))
>>>>> -			return ERR_CAST(ctx);
>>>>> -
>>>>> -		/* wait the page to be moved by cleaning */
>>>>> -		f2fs_wait_on_block_writeback(sbi, blkaddr);
>>>>> -	}
>>>>> +	struct bio_post_read_ctx *ctx;
>>>>> +	unsigned int post_read_steps = 0;
>>>>>  
>>>>>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
>>>>> -	if (!bio) {
>>>>> -		if (ctx)
>>>>> -			fscrypt_release_ctx(ctx);
>>>>> +	if (!bio)
>>>>>  		return ERR_PTR(-ENOMEM);
>>>>> -	}
>>>>>  	f2fs_target_device(sbi, blkaddr, bio);
>>>>>  	bio->bi_end_io = f2fs_read_end_io;
>>>>> -	bio->bi_private = ctx;
>>>>
>>>> bio->bi_private = NULL;
>>>>
>>>
>>> I don't see why.  ->bi_private is NULL by default.
>>
>> As we will check bi_private in read_end_io anyway, if it is not NULL, we will
>> parse it as an ctx, am I missing something?
>>
> 
> We're allocating a new bio.  New bios have NULL ->bi_private.

What I concern is that since we will port last developed code to old kernel by
ourselves, I don't want to make f2fs code rely on block layer code's robust, so
I'd like to NULL bi_private by f2fs.

I checked history of bio_init(), seems that it started to initialize bi_private
from very early version. So, alright, for new kernel, it's will not cause any
problem.

Thanks,

> 
>> Thanks,
>>
>>>
>>>>> +	bio_post_read_ctx_pool =
>>>>> +		mempool_create_slab_pool(128, bio_post_read_ctx_cache);
>>>>
>>>> #define MAX_POST_READ_CACHE_SIZE	128
>>>>
>>>
>>> Yes, that makes sense.
>>>
> 
> Actually it's the number of contexts preallocated in the mempool, so I'm going
> to call it NUM_PREALLOC_POST_READ_CTXS.  It's similar to
> 'num_prealloc_crypto_ctxs' in fs/crypto/crypto.c.
> 
> Eric
> 
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
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> 
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Patch
diff mbox

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 39225519de1c..ec70de0cd1d5 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -30,6 +30,9 @@ 
 #include "trace.h"
 #include <trace/events/f2fs.h>
 
+static struct kmem_cache *bio_post_read_ctx_cache;
+static mempool_t *bio_post_read_ctx_pool;
+
 static bool __is_cp_guaranteed(struct page *page)
 {
 	struct address_space *mapping = page->mapping;
@@ -50,11 +53,77 @@  static bool __is_cp_guaranteed(struct page *page)
 	return false;
 }
 
-static void f2fs_read_end_io(struct bio *bio)
+/* postprocessing steps for read bios */
+enum bio_post_read_step {
+	STEP_INITIAL = 0,
+	STEP_DECRYPT,
+};
+
+struct bio_post_read_ctx {
+	struct bio *bio;
+	struct work_struct work;
+	unsigned int cur_step;
+	unsigned int enabled_steps;
+};
+
+static void __read_end_io(struct bio *bio)
 {
-	struct bio_vec *bvec;
+	struct page *page;
+	struct bio_vec *bv;
 	int i;
 
+	bio_for_each_segment_all(bv, bio, i) {
+		page = bv->bv_page;
+
+		/* PG_error was set if any post_read step failed */
+		if (bio->bi_status || PageError(page)) {
+			ClearPageUptodate(page);
+			SetPageError(page);
+		} else {
+			SetPageUptodate(page);
+		}
+		unlock_page(page);
+	}
+	if (bio->bi_private)
+		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
+	bio_put(bio);
+}
+
+static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
+
+static void decrypt_work(struct work_struct *work)
+{
+	struct bio_post_read_ctx *ctx =
+		container_of(work, struct bio_post_read_ctx, work);
+
+	fscrypt_decrypt_bio(ctx->bio);
+
+	bio_post_read_processing(ctx);
+}
+
+static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
+{
+	switch (++ctx->cur_step) {
+	case STEP_DECRYPT:
+		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
+			INIT_WORK(&ctx->work, decrypt_work);
+			fscrypt_enqueue_decrypt_work(&ctx->work);
+			return;
+		}
+		ctx->cur_step++;
+		/* fall-through */
+	default:
+		__read_end_io(ctx->bio);
+	}
+}
+
+static bool f2fs_bio_post_read_required(struct bio *bio)
+{
+	return bio->bi_private && !bio->bi_status;
+}
+
+static void f2fs_read_end_io(struct bio *bio)
+{
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 	if (time_to_inject(F2FS_P_SB(bio_first_page_all(bio)), FAULT_IO)) {
 		f2fs_show_injection_info(FAULT_IO);
@@ -62,28 +131,15 @@  static void f2fs_read_end_io(struct bio *bio)
 	}
 #endif
 
-	if (f2fs_bio_encrypted(bio)) {
-		if (bio->bi_status) {
-			fscrypt_release_ctx(bio->bi_private);
-		} else {
-			fscrypt_enqueue_decrypt_bio(bio->bi_private, bio);
-			return;
-		}
-	}
-
-	bio_for_each_segment_all(bvec, bio, i) {
-		struct page *page = bvec->bv_page;
+	if (f2fs_bio_post_read_required(bio)) {
+		struct bio_post_read_ctx *ctx = bio->bi_private;
 
-		if (!bio->bi_status) {
-			if (!PageUptodate(page))
-				SetPageUptodate(page);
-		} else {
-			ClearPageUptodate(page);
-			SetPageError(page);
-		}
-		unlock_page(page);
+		ctx->cur_step = STEP_INITIAL;
+		bio_post_read_processing(ctx);
+		return;
 	}
-	bio_put(bio);
+
+	__read_end_io(bio);
 }
 
 static void f2fs_write_end_io(struct bio *bio)
@@ -481,29 +537,33 @@  static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
 							 unsigned nr_pages)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
-	struct fscrypt_ctx *ctx = NULL;
 	struct bio *bio;
-
-	if (f2fs_encrypted_file(inode)) {
-		ctx = fscrypt_get_ctx(inode, GFP_NOFS);
-		if (IS_ERR(ctx))
-			return ERR_CAST(ctx);
-
-		/* wait the page to be moved by cleaning */
-		f2fs_wait_on_block_writeback(sbi, blkaddr);
-	}
+	struct bio_post_read_ctx *ctx;
+	unsigned int post_read_steps = 0;
 
 	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
-	if (!bio) {
-		if (ctx)
-			fscrypt_release_ctx(ctx);
+	if (!bio)
 		return ERR_PTR(-ENOMEM);
-	}
 	f2fs_target_device(sbi, blkaddr, bio);
 	bio->bi_end_io = f2fs_read_end_io;
-	bio->bi_private = ctx;
 	bio_set_op_attrs(bio, REQ_OP_READ, 0);
 
+	if (f2fs_encrypted_file(inode))
+		post_read_steps |= 1 << STEP_DECRYPT;
+	if (post_read_steps) {
+		ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
+		if (!ctx) {
+			bio_put(bio);
+			return ERR_PTR(-ENOMEM);
+		}
+		ctx->bio = bio;
+		ctx->enabled_steps = post_read_steps;
+		bio->bi_private = ctx;
+
+		/* wait the page to be moved by cleaning */
+		f2fs_wait_on_block_writeback(sbi, blkaddr);
+	}
+
 	return bio;
 }
 
@@ -1525,7 +1585,7 @@  static int encrypt_one_page(struct f2fs_io_info *fio)
 	if (!f2fs_encrypted_file(inode))
 		return 0;
 
-	/* wait for GCed encrypted page writeback */
+	/* wait for GCed page writeback via META_MAPPING */
 	f2fs_wait_on_block_writeback(fio->sbi, fio->old_blkaddr);
 
 retry_encrypt:
@@ -2222,8 +2282,8 @@  static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 
 	f2fs_wait_on_page_writeback(page, DATA, false);
 
-	/* wait for GCed encrypted page writeback */
-	if (f2fs_encrypted_file(inode))
+	/* wait for GCed page writeback via META_MAPPING */
+	if (f2fs_post_read_required(inode))
 		f2fs_wait_on_block_writeback(sbi, blkaddr);
 
 	if (len == PAGE_SIZE || PageUptodate(page))
@@ -2555,3 +2615,26 @@  const struct address_space_operations f2fs_dblock_aops = {
 	.migratepage    = f2fs_migrate_page,
 #endif
 };
+
+int __init f2fs_init_post_read_processing(void)
+{
+	bio_post_read_ctx_cache = KMEM_CACHE(bio_post_read_ctx, 0);
+	if (!bio_post_read_ctx_cache)
+		goto fail;
+	bio_post_read_ctx_pool =
+		mempool_create_slab_pool(128, bio_post_read_ctx_cache);
+	if (!bio_post_read_ctx_pool)
+		goto fail_free_cache;
+	return 0;
+
+fail_free_cache:
+	kmem_cache_destroy(bio_post_read_ctx_cache);
+fail:
+	return -ENOMEM;
+}
+
+void __exit f2fs_destroy_post_read_processing(void)
+{
+	mempool_destroy(bio_post_read_ctx_pool);
+	kmem_cache_destroy(bio_post_read_ctx_cache);
+}
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 1df7f10476d6..ea92c18db624 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2858,6 +2858,8 @@  void destroy_checkpoint_caches(void);
 /*
  * data.c
  */
+int f2fs_init_post_read_processing(void);
+void f2fs_destroy_post_read_processing(void);
 void f2fs_submit_merged_write(struct f2fs_sb_info *sbi, enum page_type type);
 void f2fs_submit_merged_write_cond(struct f2fs_sb_info *sbi,
 				struct inode *inode, nid_t ino, pgoff_t idx,
@@ -3218,9 +3220,13 @@  static inline void f2fs_set_encrypted_inode(struct inode *inode)
 #endif
 }
 
-static inline bool f2fs_bio_encrypted(struct bio *bio)
+/*
+ * Returns true if the reads of the inode's data need to undergo some
+ * postprocessing step, like decryption or authenticity verification.
+ */
+static inline bool f2fs_post_read_required(struct inode *inode)
 {
-	return bio->bi_private != NULL;
+	return f2fs_encrypted_file(inode);
 }
 
 #define F2FS_FEATURE_FUNCS(name, flagname) \
@@ -3288,7 +3294,7 @@  static inline bool f2fs_may_encrypt(struct inode *inode)
 
 static inline bool f2fs_force_buffered_io(struct inode *inode, int rw)
 {
-	return (f2fs_encrypted_file(inode) ||
+	return (f2fs_post_read_required(inode) ||
 			(rw == WRITE && test_opt(F2FS_I_SB(inode), LFS)) ||
 			F2FS_I_SB(inode)->s_ndevs);
 }
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 6b94f19b3fa8..cc08956334a0 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -110,8 +110,8 @@  static int f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	/* fill the page */
 	f2fs_wait_on_page_writeback(page, DATA, false);
 
-	/* wait for GCed encrypted page writeback */
-	if (f2fs_encrypted_file(inode))
+	/* wait for GCed page writeback via META_MAPPING */
+	if (f2fs_post_read_required(inode))
 		f2fs_wait_on_block_writeback(sbi, dn.data_blkaddr);
 
 out_sem:
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 9327411fd93b..70418b34c5f6 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -850,8 +850,8 @@  static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 			if (IS_ERR(inode) || is_bad_inode(inode))
 				continue;
 
-			/* if encrypted inode, let's go phase 3 */
-			if (f2fs_encrypted_file(inode)) {
+			/* if inode uses special I/O path, let's go phase 3 */
+			if (f2fs_post_read_required(inode)) {
 				add_gc_inode(gc_list, inode);
 				continue;
 			}
@@ -899,7 +899,7 @@  static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 
 			start_bidx = start_bidx_of_node(nofs, inode)
 								+ ofs_in_node;
-			if (f2fs_encrypted_file(inode))
+			if (f2fs_post_read_required(inode))
 				move_data_block(inode, start_bidx, segno, off);
 			else
 				move_data_page(inode, start_bidx, gc_type,
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 265da200daa8..767e41d944c6 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -25,7 +25,7 @@  bool f2fs_may_inline_data(struct inode *inode)
 	if (i_size_read(inode) > MAX_INLINE_DATA(inode))
 		return false;
 
-	if (f2fs_encrypted_file(inode))
+	if (f2fs_post_read_required(inode))
 		return false;
 
 	return true;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 42d564c5ccd0..f31643718c76 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3092,8 +3092,13 @@  static int __init init_f2fs_fs(void)
 	err = f2fs_create_root_stats();
 	if (err)
 		goto free_filesystem;
+	err = f2fs_init_post_read_processing();
+	if (err)
+		goto free_root_stats;
 	return 0;
 
+free_root_stats:
+	f2fs_destroy_root_stats();
 free_filesystem:
 	unregister_filesystem(&f2fs_fs_type);
 free_shrinker:
@@ -3116,6 +3121,7 @@  static int __init init_f2fs_fs(void)
 
 static void __exit exit_f2fs_fs(void)
 {
+	f2fs_destroy_post_read_processing();
 	f2fs_destroy_root_stats();
 	unregister_filesystem(&f2fs_fs_type);
 	unregister_shrinker(&f2fs_shrinker_info);