diff mbox series

[v11,03/14] btrfs: don't advance offset for compressed bios in btrfs_csum_one_bio()

Message ID 40d0097d3b5e1ba14e6b6d090ba6d0e5c046985f.1630514529.git.osandov@fb.com (mailing list archive)
State New, archived
Headers show
Series btrfs: add ioctls and send/receive support for reading/writing compressed data | expand

Commit Message

Omar Sandoval Sept. 1, 2021, 5 p.m. UTC 
From: Omar Sandoval <osandov@fb.com>

btrfs_csum_one_bio() loops over each filesystem block in the bio while
keeping a cursor of its current logical position in the file in order to
look up the ordered extent to add the checksums to. However, this
doesn't make much sense for compressed extents, as a sector on disk does
not correspond to a sector of decompressed file data. It happens to work
because 1) the compressed bio always covers one ordered extent and 2)
the size of the bio is always less than the size of the ordered extent.
However, the second point will not always be true for encoded writes.

Let's add a boolean parameter to btrfs_csum_one_bio() to indicate that
it can assume that the bio only covers one ordered extent. Since we're
already changing the signature, let's get rid of the contig parameter
and make it implied by the offset parameter, similar to the change we
recently made to btrfs_lookup_bio_sums(). Additionally, let's rename
nr_sectors to blockcount to make it clear that it's the number of
filesystem blocks, not the number of 512-byte sectors.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 fs/btrfs/compression.c |  5 +++--
 fs/btrfs/ctree.h       |  2 +-
 fs/btrfs/file-item.c   | 32 ++++++++++++++------------------
 fs/btrfs/inode.c       |  8 ++++----
 4 files changed, 22 insertions(+), 25 deletions(-)

Comments

Nikolay Borisov Oct. 14, 2021, 12:05 p.m. UTC | #1 
On 1.09.21 г. 20:00, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> btrfs_csum_one_bio() loops over each filesystem block in the bio while
> keeping a cursor of its current logical position in the file in order to
> look up the ordered extent to add the checksums to. However, this
> doesn't make much sense for compressed extents, as a sector on disk does
> not correspond to a sector of decompressed file data. It happens to work
> because 1) the compressed bio always covers one ordered extent and 2)
> the size of the bio is always less than the size of the ordered extent.
> However, the second point will not always be true for encoded writes.
> 
> Let's add a boolean parameter to btrfs_csum_one_bio() to indicate that
> it can assume that the bio only covers one ordered extent. Since we're
> already changing the signature, let's get rid of the contig parameter
> and make it implied by the offset parameter, similar to the change we
> recently made to btrfs_lookup_bio_sums(). Additionally, let's rename
> nr_sectors to blockcount to make it clear that it's the number of
> filesystem blocks, not the number of 512-byte sectors.
> 
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Omar Sandoval <osandov@fb.com>

Code-wise this looks, though I don't know why we are guaranteed that a
compressed extent will only cover a single OE. But I trust you so:

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Omar Sandoval Oct. 18, 2021, 6:09 p.m. UTC | #2 
On Thu, Oct 14, 2021 at 03:05:54PM +0300, Nikolay Borisov wrote:
> 
> 
> On 1.09.21 г. 20:00, Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> > 
> > btrfs_csum_one_bio() loops over each filesystem block in the bio while
> > keeping a cursor of its current logical position in the file in order to
> > look up the ordered extent to add the checksums to. However, this
> > doesn't make much sense for compressed extents, as a sector on disk does
> > not correspond to a sector of decompressed file data. It happens to work
> > because 1) the compressed bio always covers one ordered extent and 2)
> > the size of the bio is always less than the size of the ordered extent.
> > However, the second point will not always be true for encoded writes.
> > 
> > Let's add a boolean parameter to btrfs_csum_one_bio() to indicate that
> > it can assume that the bio only covers one ordered extent. Since we're
> > already changing the signature, let's get rid of the contig parameter
> > and make it implied by the offset parameter, similar to the change we
> > recently made to btrfs_lookup_bio_sums(). Additionally, let's rename
> > nr_sectors to blockcount to make it clear that it's the number of
> > filesystem blocks, not the number of 512-byte sectors.
> > 
> > Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> > Signed-off-by: Omar Sandoval <osandov@fb.com>
> 
> Code-wise this looks, though I don't know why we are guaranteed that a
> compressed extent will only cover a single OE.

See submit_compressed_extents(): we always add an ordered extent that
covers the whole range that we're submitting, and then
btrfs_submit_compressed_write() creates one or more bios that are
subsets of that range.

> But I trust you so:
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>

Thanks!
diff mbox series

Patch

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 7869ad12bc6e..e645b3c2f09a 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -480,7 +480,8 @@  blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 			BUG_ON(ret); /* -ENOMEM */
 
 			if (!skip_sum) {
-				ret = btrfs_csum_one_bio(inode, bio, start, 1);
+				ret = btrfs_csum_one_bio(inode, bio, start,
+							 true);
 				BUG_ON(ret); /* -ENOMEM */
 			}
 
@@ -516,7 +517,7 @@  blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	BUG_ON(ret); /* -ENOMEM */
 
 	if (!skip_sum) {
-		ret = btrfs_csum_one_bio(inode, bio, start, 1);
+		ret = btrfs_csum_one_bio(inode, bio, start, true);
 		BUG_ON(ret); /* -ENOMEM */
 	}
 
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 38870ae46cbb..8ea383cac13b 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3115,7 +3115,7 @@  int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   struct btrfs_ordered_sum *sums);
 blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
-				u64 file_start, int contig);
+				u64 offset, bool one_ordered);
 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 			     struct list_head *list, int search_commit);
 void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 2673c6ba7a4e..aa5fb66e6987 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -614,28 +614,28 @@  int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
  * btrfs_csum_one_bio - Calculates checksums of the data contained inside a bio
  * @inode:	 Owner of the data inside the bio
  * @bio:	 Contains the data to be checksummed
- * @file_start:  offset in file this bio begins to describe
- * @contig:	 Boolean. If true/1 means all bio vecs in this bio are
- *		 contiguous and they begin at @file_start in the file. False/0
- *		 means this bio can contain potentially discontiguous bio vecs
- *		 so the logical offset of each should be calculated separately.
+ * @offset:      If (u64)-1, @bio may contain discontiguous bio vecs, so the
+ *               file offsets are determined from the page offsets in the bio.
+ *               Otherwise, this is the starting file offset of the bio vecs in
+ *               @bio, which must be contiguous.
+ * @one_ordered: If true, @bio only refers to one ordered extent.
  */
 blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
-		       u64 file_start, int contig)
+				u64 offset, bool one_ordered)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
 	struct btrfs_ordered_sum *sums;
 	struct btrfs_ordered_extent *ordered = NULL;
+	const bool use_page_offsets = (offset == (u64)-1);
 	char *data;
 	struct bvec_iter iter;
 	struct bio_vec bvec;
 	int index;
-	int nr_sectors;
+	int blockcount;
 	unsigned long total_bytes = 0;
 	unsigned long this_sum_bytes = 0;
 	int i;
-	u64 offset;
 	unsigned nofs_flag;
 
 	nofs_flag = memalloc_nofs_save();
@@ -649,18 +649,13 @@  blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
 	sums->len = bio->bi_iter.bi_size;
 	INIT_LIST_HEAD(&sums->list);
 
-	if (contig)
-		offset = file_start;
-	else
-		offset = 0; /* shut up gcc */
-
 	sums->bytenr = bio->bi_iter.bi_sector << 9;
 	index = 0;
 
 	shash->tfm = fs_info->csum_shash;
 
 	bio_for_each_segment(bvec, bio, iter) {
-		if (!contig)
+		if (use_page_offsets)
 			offset = page_offset(bvec.bv_page) + bvec.bv_offset;
 
 		if (!ordered) {
@@ -668,13 +663,14 @@  blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
 			BUG_ON(!ordered); /* Logic error */
 		}
 
-		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info,
+		blockcount = BTRFS_BYTES_TO_BLKS(fs_info,
 						 bvec.bv_len + fs_info->sectorsize
 						 - 1);
 
-		for (i = 0; i < nr_sectors; i++) {
-			if (offset >= ordered->file_offset + ordered->num_bytes ||
-			    offset < ordered->file_offset) {
+		for (i = 0; i < blockcount; i++) {
+			if (!one_ordered &&
+			    !in_range(offset, ordered->file_offset,
+				      ordered->num_bytes)) {
 				unsigned long bytes_left;
 
 				sums->len = this_sum_bytes;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 0517f31a3bed..8063d05e4a20 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2286,7 +2286,7 @@  int btrfs_bio_fits_in_stripe(struct page *page, size_t size, struct bio *bio,
 static blk_status_t btrfs_submit_bio_start(struct inode *inode, struct bio *bio,
 					   u64 dio_file_offset)
 {
-	return btrfs_csum_one_bio(BTRFS_I(inode), bio, 0, 0);
+	return btrfs_csum_one_bio(BTRFS_I(inode), bio, (u64)-1, false);
 }
 
 /*
@@ -2538,7 +2538,7 @@  blk_status_t btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 					  0, btrfs_submit_bio_start);
 		goto out;
 	} else if (!skip_sum) {
-		ret = btrfs_csum_one_bio(BTRFS_I(inode), bio, 0, 0);
+		ret = btrfs_csum_one_bio(BTRFS_I(inode), bio, (u64)-1, false);
 		if (ret)
 			goto out;
 	}
@@ -8140,7 +8140,7 @@  static blk_status_t btrfs_submit_bio_start_direct_io(struct inode *inode,
 						     struct bio *bio,
 						     u64 dio_file_offset)
 {
-	return btrfs_csum_one_bio(BTRFS_I(inode), bio, dio_file_offset, 1);
+	return btrfs_csum_one_bio(BTRFS_I(inode), bio, dio_file_offset, false);
 }
 
 static void btrfs_end_dio_bio(struct bio *bio)
@@ -8199,7 +8199,7 @@  static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
 		 * If we aren't doing async submit, calculate the csum of the
 		 * bio now.
 		 */
-		ret = btrfs_csum_one_bio(BTRFS_I(inode), bio, file_offset, 1);
+		ret = btrfs_csum_one_bio(BTRFS_I(inode), bio, file_offset, false);
 		if (ret)
 			goto err;
 	} else {