[09/35] btrfs: protect space cache inode alloc with nofs
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Message ID 20180830174225.2200-10-josef@toxicpanda.com
State New
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Series
  • My current patch queue
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Commit Message

Josef Bacik Aug. 30, 2018, 5:41 p.m. UTC
If we're allocating a new space cache inode it's likely going to be
under a transaction handle, so we need to use memalloc_nofs_save() in
order to avoid deadlocks, and more importantly lockdep messages that
make xfstests fail.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/free-space-cache.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Omar Sandoval Sept. 1, 2018, 12:14 a.m. UTC | #1
On Thu, Aug 30, 2018 at 01:41:59PM -0400, Josef Bacik wrote:
> If we're allocating a new space cache inode it's likely going to be
> under a transaction handle, so we need to use memalloc_nofs_save() in
> order to avoid deadlocks, and more importantly lockdep messages that
> make xfstests fail.

Could use a comment where we call memalloc_nofs_save(). Otherwise,

Reviewed-by: Omar Sandoval <osandov@fb.com>

> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
>  fs/btrfs/free-space-cache.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index c3888c113d81..db93a5f035a0 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -10,6 +10,7 @@
>  #include <linux/math64.h>
>  #include <linux/ratelimit.h>
>  #include <linux/error-injection.h>
> +#include <linux/sched/mm.h>
>  #include "ctree.h"
>  #include "free-space-cache.h"
>  #include "transaction.h"
> @@ -47,6 +48,7 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
>  	struct btrfs_free_space_header *header;
>  	struct extent_buffer *leaf;
>  	struct inode *inode = NULL;
> +	unsigned nofs_flag;
>  	int ret;
>  
>  	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
> @@ -68,7 +70,9 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
>  	btrfs_disk_key_to_cpu(&location, &disk_key);
>  	btrfs_release_path(path);
>  
> +	nofs_flag = memalloc_nofs_save();
>  	inode = btrfs_iget(fs_info->sb, &location, root, NULL);
> +	memalloc_nofs_restore(nofs_flag);
>  	if (IS_ERR(inode))
>  		return inode;
>  
> -- 
> 2.14.3
>

Patch
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diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index c3888c113d81..db93a5f035a0 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -10,6 +10,7 @@ 
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
 #include <linux/error-injection.h>
+#include <linux/sched/mm.h>
 #include "ctree.h"
 #include "free-space-cache.h"
 #include "transaction.h"
@@ -47,6 +48,7 @@  static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
 	struct btrfs_free_space_header *header;
 	struct extent_buffer *leaf;
 	struct inode *inode = NULL;
+	unsigned nofs_flag;
 	int ret;
 
 	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
@@ -68,7 +70,9 @@  static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
 	btrfs_disk_key_to_cpu(&location, &disk_key);
 	btrfs_release_path(path);
 
+	nofs_flag = memalloc_nofs_save();
 	inode = btrfs_iget(fs_info->sb, &location, root, NULL);
+	memalloc_nofs_restore(nofs_flag);
 	if (IS_ERR(inode))
 		return inode;