2024-03-11 12:30:21

by Zhang Yi

Subject: [PATCH 1/4] xfs: match lock mode in xfs_buffered_write_iomap_begin()

From: Zhang Yi <[email protected]>

Commit 1aa91d9c9933 ("xfs: Add async buffered write support") replace
xfs_ilock(XFS_ILOCK_EXCL) with xfs_ilock_for_iomap() when locking the
writing inode, and a new variable lockmode is used to indicate the lock
mode. Although the lockmode should always be XFS_ILOCK_EXCL, it's still
better to use this variable instead of useing XFS_ILOCK_EXCL directly
when unlocking the inode.

Fixes: 1aa91d9c9933 ("xfs: Add async buffered write support")
Signed-off-by: Zhang Yi <[email protected]>
---
fs/xfs/xfs_iomap.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 18c8f168b153..ccf83e72d8ca 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1149,13 +1149,13 @@ xfs_buffered_write_iomap_begin(
* them out if the write happens to fail.
*/
seq = xfs_iomap_inode_sequence(ip, IOMAP_F_NEW);
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ xfs_iunlock(ip, lockmode);
trace_xfs_iomap_alloc(ip, offset, count, allocfork, &imap);
return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW, seq);

found_imap:
seq = xfs_iomap_inode_sequence(ip, 0);
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ xfs_iunlock(ip, lockmode);
return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);

found_cow:
@@ -1165,17 +1165,17 @@ xfs_buffered_write_iomap_begin(
if (error)
goto out_unlock;
seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ xfs_iunlock(ip, lockmode);
return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
IOMAP_F_SHARED, seq);
}

xfs_trim_extent(&cmap, offset_fsb, imap.br_startoff - offset_fsb);
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ xfs_iunlock(ip, lockmode);
return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, 0, seq);

out_unlock:
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ xfs_iunlock(ip, lockmode);
return error;
}

--
2.39.2

2024-03-11 15:36:21

by Darrick J. Wong

Subject: Re: [PATCH 1/4] xfs: match lock mode in xfs_buffered_write_iomap_begin()

On Mon, Mar 11, 2024 at 08:22:52PM +0800, Zhang Yi wrote:
> From: Zhang Yi <[email protected]>
>
> Commit 1aa91d9c9933 ("xfs: Add async buffered write support") replace
> xfs_ilock(XFS_ILOCK_EXCL) with xfs_ilock_for_iomap() when locking the
> writing inode, and a new variable lockmode is used to indicate the lock
> mode. Although the lockmode should always be XFS_ILOCK_EXCL, it's still
> better to use this variable instead of useing XFS_ILOCK_EXCL directly
> when unlocking the inode.
>
> Fixes: 1aa91d9c9933 ("xfs: Add async buffered write support")

AFAICT, xfs_ilock_for_iomap can change lockmode from SHARED->EXCL, but
never changed away from EXCL, right? And xfs_buffered_write_iomap_begin
sets it to EXCL (and never changes it), right?

This seems like more of a code cleanup/logic bomb removal than an actual
defect that someone could actually hit, correct?

If the answers are {yes, yes, yes} then:
Reviewed-by: Darrick J. Wong <[email protected]>

--D


> Signed-off-by: Zhang Yi <[email protected]>
> ---
> fs/xfs/xfs_iomap.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 18c8f168b153..ccf83e72d8ca 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -1149,13 +1149,13 @@ xfs_buffered_write_iomap_begin(
> * them out if the write happens to fail.
> */
> seq = xfs_iomap_inode_sequence(ip, IOMAP_F_NEW);
> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + xfs_iunlock(ip, lockmode);
> trace_xfs_iomap_alloc(ip, offset, count, allocfork, &imap);
> return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW, seq);
>
> found_imap:
> seq = xfs_iomap_inode_sequence(ip, 0);
> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + xfs_iunlock(ip, lockmode);
> return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);
>
> found_cow:
> @@ -1165,17 +1165,17 @@ xfs_buffered_write_iomap_begin(
> if (error)
> goto out_unlock;
> seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + xfs_iunlock(ip, lockmode);
> return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
> IOMAP_F_SHARED, seq);
> }
>
> xfs_trim_extent(&cmap, offset_fsb, imap.br_startoff - offset_fsb);
> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + xfs_iunlock(ip, lockmode);
> return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, 0, seq);
>
> out_unlock:
> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + xfs_iunlock(ip, lockmode);
> return error;
> }
>
> --
> 2.39.2
>
>

2024-03-12 08:18:57

by Zhang Yi

Subject: Re: [PATCH 1/4] xfs: match lock mode in xfs_buffered_write_iomap_begin()

On 2024/3/11 23:34, Darrick J. Wong wrote:
> On Mon, Mar 11, 2024 at 08:22:52PM +0800, Zhang Yi wrote:
>> From: Zhang Yi <[email protected]>
>>
>> Commit 1aa91d9c9933 ("xfs: Add async buffered write support") replace
>> xfs_ilock(XFS_ILOCK_EXCL) with xfs_ilock_for_iomap() when locking the
>> writing inode, and a new variable lockmode is used to indicate the lock
>> mode. Although the lockmode should always be XFS_ILOCK_EXCL, it's still
>> better to use this variable instead of useing XFS_ILOCK_EXCL directly
>> when unlocking the inode.
>>
>> Fixes: 1aa91d9c9933 ("xfs: Add async buffered write support")
>
> AFAICT, xfs_ilock_for_iomap can change lockmode from SHARED->EXCL, but
> never changed away from EXCL, right?

Yes.

> And xfs_buffered_write_iomap_begin
> sets it to EXCL (and never changes it), right?

Yes.

>
> This seems like more of a code cleanup/logic bomb removal than an actual
> defect that someone could actually hit, correct?
>

Yes, it's not a real problem.

> If the answers are {yes, yes, yes} then:
> Reviewed-by: Darrick J. Wong <[email protected]>
>
> --D
>
>
>> Signed-off-by: Zhang Yi <[email protected]>
>> ---
>> fs/xfs/xfs_iomap.c | 10 +++++-----
>> 1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
>> index 18c8f168b153..ccf83e72d8ca 100644
>> --- a/fs/xfs/xfs_iomap.c
>> +++ b/fs/xfs/xfs_iomap.c
>> @@ -1149,13 +1149,13 @@ xfs_buffered_write_iomap_begin(
>> * them out if the write happens to fail.
>> */
>> seq = xfs_iomap_inode_sequence(ip, IOMAP_F_NEW);
>> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
>> + xfs_iunlock(ip, lockmode);
>> trace_xfs_iomap_alloc(ip, offset, count, allocfork, &imap);
>> return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW, seq);
>>
>> found_imap:
>> seq = xfs_iomap_inode_sequence(ip, 0);
>> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
>> + xfs_iunlock(ip, lockmode);
>> return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);
>>
>> found_cow:
>> @@ -1165,17 +1165,17 @@ xfs_buffered_write_iomap_begin(
>> if (error)
>> goto out_unlock;
>> seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
>> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
>> + xfs_iunlock(ip, lockmode);
>> return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
>> IOMAP_F_SHARED, seq);
>> }
>>
>> xfs_trim_extent(&cmap, offset_fsb, imap.br_startoff - offset_fsb);
>> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
>> + xfs_iunlock(ip, lockmode);
>> return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, 0, seq);
>>
>> out_unlock:
>> - xfs_iunlock(ip, XFS_ILOCK_EXCL);
>> + xfs_iunlock(ip, lockmode);
>> return error;
>> }
>>
>> --
>> 2.39.2
>>
>>

2024-03-12 12:17:30

by Christoph Hellwig

Subject: Re: [PATCH 1/4] xfs: match lock mode in xfs_buffered_write_iomap_begin()

Looks good:

Reviewed-by: Christoph Hellwig <[email protected]>