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@xxxxxxxxxxxxx
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