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xfs: lock out page faults from extent swap operations

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Extent swap operations are another extent manipulation operation
that we need to ensure does not race against mmap page faults. The
current code returns if the file is mapped prior to the swap being
done, but it could potentially race against new page faults while
the swap is in progress. Hence we should use the XFS_MMAPLOCK_EXCL
for this operation, too.

While there, fix the error path handling that can result in double
unlocks of the inodes when cancelling the swapext transaction.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Dave Chinner 2015-02-23 21:47:29 +11:00 committed by Dave Chinner
parent 0f9160b444
commit 723cac4847
1 changed files with 15 additions and 16 deletions
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31
fs/xfs/xfs_bmap_util.c
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@ -1599,13 +1599,6 @@ xfs_swap_extent_flush(
/* Verify O_DIRECT for ftmp */ /* Verify O_DIRECT for ftmp */
if (VFS_I(ip)->i_mapping->nrpages) if (VFS_I(ip)->i_mapping->nrpages)
return -EINVAL; return -EINVAL;
/*
* Don't try to swap extents on mmap()d files because we can't lock
* out races against page faults safely.
*/
if (mapping_mapped(VFS_I(ip)->i_mapping))
return -EBUSY;
return 0; return 0;
} }
@ -1633,13 +1626,14 @@ xfs_swap_extents(
} }
/* /*
* Lock up the inodes against other IO and truncate to begin with. * Lock the inodes against other IO, page faults and truncate to
* Then we can ensure the inodes are flushed and have no page cache * begin with. Then we can ensure the inodes are flushed and have no
* safely. Once we have done this we can take the ilocks and do the rest * page cache safely. Once we have done this we can take the ilocks and
* of the checks. * do the rest of the checks.
*/ */
lock_flags = XFS_IOLOCK_EXCL; lock_flags = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
xfs_lock_two_inodes(ip, tip, XFS_IOLOCK_EXCL); xfs_lock_two_inodes(ip, tip, XFS_IOLOCK_EXCL);
xfs_lock_two_inodes(ip, tip, XFS_MMAPLOCK_EXCL);
/* Verify that both files have the same format */ /* Verify that both files have the same format */
if ((ip->i_d.di_mode & S_IFMT) != (tip->i_d.di_mode & S_IFMT)) { if ((ip->i_d.di_mode & S_IFMT) != (tip->i_d.di_mode & S_IFMT)) {
@ -1666,8 +1660,16 @@ xfs_swap_extents(
xfs_trans_cancel(tp, 0); xfs_trans_cancel(tp, 0);
goto out_unlock; goto out_unlock;
} }
/*
* Lock and join the inodes to the tansaction so that transaction commit
* or cancel will unlock the inodes from this point onwards.
*/
xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL); xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
lock_flags |= XFS_ILOCK_EXCL; lock_flags |= XFS_ILOCK_EXCL;
xfs_trans_ijoin(tp, ip, lock_flags);
xfs_trans_ijoin(tp, tip, lock_flags);
/* Verify all data are being swapped */ /* Verify all data are being swapped */
if (sxp->sx_offset != 0 || if (sxp->sx_offset != 0 ||
@ -1720,9 +1722,6 @@ xfs_swap_extents(
goto out_trans_cancel; goto out_trans_cancel;
} }
xfs_trans_ijoin(tp, ip, lock_flags);
xfs_trans_ijoin(tp, tip, lock_flags);
/* /*
* Before we've swapped the forks, lets set the owners of the forks * Before we've swapped the forks, lets set the owners of the forks
* appropriately. We have to do this as we are demand paging the btree * appropriately. We have to do this as we are demand paging the btree
@ -1856,5 +1855,5 @@ out_unlock:
out_trans_cancel: out_trans_cancel:
xfs_trans_cancel(tp, 0); xfs_trans_cancel(tp, 0);
goto out_unlock; goto out;
} }