Re: [PATCH] Btrfs: fix leak of subvolume writers counter

[Liu Bo]

On Sat, Jan 28, 2017 at 06:06:54AM +, fdman...@kernel.org wrote:
> From: Robbie Ko 
> 
> When falling back from a nocow write to a regular cow write, we were
> leaking the subvolume writers counter in 2 situations, preventing
> snapshot creation from ever completing in the future, as it waits
> for that counter to go down to zero before the snapshot creation
> starts.
> 
> In run_delalloc_nocow, maybe not release subv_writers conter,
> will lead to create snapshot hang.

Reviewed-by: Liu Bo 

Thanks,

-liubo
> 
> Signed-off-by: Robbie Ko 
> Reviewed-by: Filipe Manana 
> [Improved changelog and subject]
> Signed-off-by: Filipe Manana 
> ---
>  fs/btrfs/inode.c | 10 --
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index a713d9d..7221d66 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -1404,10 +1404,16 @@ static noinline int run_delalloc_nocow(struct inode 
> *inode,
>* either valid or do not exist.
>*/
>   if (csum_exist_in_range(fs_info, disk_bytenr,
> - num_bytes))
> + num_bytes)) {
> + if (!nolock)
> + btrfs_end_write_no_snapshoting(root);
>   goto out_check;
> - if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr))
> + }
> + if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr)) {
> + if (!nolock)
> + btrfs_end_write_no_snapshoting(root);
>   goto out_check;
> + }
>   nocow = 1;
>   } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
>   extent_end = found_key.offset +
> -- 
> 2.7.0.rc3
> 
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[PATCH] Btrfs: fix leak of subvolume writers counter

[fdmanana]

From: Robbie Ko 

When falling back from a nocow write to a regular cow write, we were
leaking the subvolume writers counter in 2 situations, preventing
snapshot creation from ever completing in the future, as it waits
for that counter to go down to zero before the snapshot creation
starts.

In run_delalloc_nocow, maybe not release subv_writers conter,
will lead to create snapshot hang.

Signed-off-by: Robbie Ko 
Reviewed-by: Filipe Manana 
[Improved changelog and subject]
Signed-off-by: Filipe Manana 
---
 fs/btrfs/inode.c | 10 --
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a713d9d..7221d66 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1404,10 +1404,16 @@ static noinline int run_delalloc_nocow(struct inode 
*inode,
 * either valid or do not exist.
 */
if (csum_exist_in_range(fs_info, disk_bytenr,
-   num_bytes))
+   num_bytes)) {
+   if (!nolock)
+   btrfs_end_write_no_snapshoting(root);
goto out_check;
-   if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr))
+   }
+   if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr)) {
+   if (!nolock)
+   btrfs_end_write_no_snapshoting(root);
goto out_check;
+   }
nocow = 1;
} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
extent_end = found_key.offset +
-- 
2.7.0.rc3

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