2017-07-05 00:02:42

by Goldwyn Rodrigues

Subject: [PATCH] btrfs: Correct assignment of pos

From: Goldwyn Rodrigues <[email protected]>

Assigning pos for usage early messes up in append mode, where
the pos is re-assigned in generic_write_checks(). Re-assign
pos to get the correct position to write from iocb->ki_pos.

Fixes: edf064e7c6fe ("btrfs: nowait aio support")
Signed-off-by: Goldwyn Rodrigues <[email protected]>
Tested-by: Markus Trippelsdorf <[email protected]>
---
fs/btrfs/file.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 59e2dccdf75b..7947781229e5 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1931,6 +1931,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
*/
update_time_for_write(inode);

+ pos = iocb->ki_pos;
start_pos = round_down(pos, fs_info->sectorsize);
oldsize = i_size_read(inode);
if (start_pos > oldsize) {
--
2.12.0

2017-07-05 00:44:46

by Marc Dionne

Subject: Re: [PATCH] btrfs: Correct assignment of pos

On Tue, Jul 4, 2017 at 9:02 PM, Goldwyn Rodrigues <[email protected]> wrote:
> From: Goldwyn Rodrigues <[email protected]>
>
> Assigning pos for usage early messes up in append mode, where
> the pos is re-assigned in generic_write_checks(). Re-assign
> pos to get the correct position to write from iocb->ki_pos.
>
> Fixes: edf064e7c6fe ("btrfs: nowait aio support")
> Signed-off-by: Goldwyn Rodrigues <[email protected]>
> Tested-by: Markus Trippelsdorf <[email protected]>
> ---
> fs/btrfs/file.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 59e2dccdf75b..7947781229e5 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1931,6 +1931,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
> */
> update_time_for_write(inode);
>
> + pos = iocb->ki_pos;
> start_pos = round_down(pos, fs_info->sectorsize);
> oldsize = i_size_read(inode);
> if (start_pos > oldsize) {
> --
> 2.12.0

For an append, shouldn't you also be using this updated pos from
generic_write_checks when calling check_can_nocow at the top of the
function?

Marc