lkml.org 
[lkml]   [2014]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: your patch "mm: Remove false WARN_ON from pagecache_isize_extended()"
On Mon, Nov 03, 2014 at 04:41:13PM +0000, Jan Beulich wrote:
> Jan,
>
> having run into that warning too, I looked into it a little, and now
> having found that patch am pretty uncertain: Both truncate_setsize()
> and pagecache_isize_extended() document that they want to be
> called with i_mutex held, so removing the WARN_ON() alone seems
> either incomplete or wrong. What I found to work without violating
> this documented requirement is the patch below.

Or, just perhaps, the comments are wrong....

Some filesystems have stronger, more robust internal serialisation
than the VFS provides with i_mutex....

> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -797,7 +797,7 @@ xfs_file_fallocate(
> FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
> return -EOPNOTSUPP;
>
> - xfs_ilock(ip, XFS_IOLOCK_EXCL);
> + xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);
> if (mode & FALLOC_FL_PUNCH_HOLE) {
> error = xfs_free_file_space(ip, offset, len);
> if (error)

The i_mutex is completely redundant here. Not to mention there are
multiple callers of these xfs_*_file_space() functions used to
implement fallocate(), and we're not about to change the locking
model for them....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com


\
 
 \ /
  Last update: 2014-11-03 23:41    [W:0.060 / U:0.352 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site