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xfs: fix swapext ilock deadlock 

xfs_swap_extents() holds the ilock over a call to
filemap_write_and_wait(), which can then try to write data and take
the ilock. That causes a self-deadlock.

Fix the deadlock and clean up the code by separating the locking
appropriately. Add a lockflags variable to track what locks we are
holding as we gain and drop them and cleanup the error handling to
always use "out_unlock" with the lockflags variable.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Dave Chinner 2014-08-04 13:29:32 +10:00 committed by Dave Chinner
parent b92cc59f69
commit 8121768321
1 changed files with 18 additions and 15 deletions
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33
fs/xfs/xfs_bmap_util.c
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@ -1686,6 +1686,7 @@ xfs_swap_extents(
int aforkblks = 0;
int taforkblks = 0;
__uint64_t tmp;
int lock_flags;
tempifp = kmem_alloc(sizeof(xfs_ifork_t), KM_MAYFAIL);
if (!tempifp) {
@ -1694,13 +1695,13 @@ xfs_swap_extents(
}
/*
* we have to do two separate lock calls here to keep lockdep
* happy. If we try to get all the locks in one call, lock will
* report false positives when we drop the ILOCK and regain them
* below.
* Lock up the inodes against other IO and truncate to begin with.
* Then we can ensure the inodes are flushed and have no page cache
* safely. Once we have done this we can take the ilocks and do the rest
* of the checks.
*/
lock_flags = XFS_IOLOCK_EXCL;
xfs_lock_two_inodes(ip, tip, XFS_IOLOCK_EXCL);
xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
/* Verify that both files have the same format */
if ((ip->i_d.di_mode & S_IFMT) != (tip->i_d.di_mode & S_IFMT)) {
@ -1719,6 +1720,9 @@ xfs_swap_extents(
goto out_unlock;
truncate_pagecache_range(VFS_I(tip), 0, -1);
xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
lock_flags |= XFS_ILOCK_EXCL;
/* Verify O_DIRECT for ftmp */
if (VFS_I(tip)->i_mapping->nrpages) {
error = -EINVAL;
@ -1773,6 +1777,7 @@ xfs_swap_extents(
xfs_iunlock(ip, XFS_ILOCK_EXCL);
xfs_iunlock(tip, XFS_ILOCK_EXCL);
lock_flags &= ~XFS_ILOCK_EXCL;
/*
* There is a race condition here since we gave up the
@ -1785,13 +1790,11 @@ xfs_swap_extents(
tp = xfs_trans_alloc(mp, XFS_TRANS_SWAPEXT);
error = xfs_trans_reserve(tp, &M_RES(mp)->tr_ichange, 0, 0);
if (error) {
xfs_iunlock(ip, XFS_IOLOCK_EXCL);
xfs_iunlock(tip, XFS_IOLOCK_EXCL);
xfs_trans_cancel(tp, 0);
goto out;
}
if (error)
goto out_trans_cancel;
xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
lock_flags |= XFS_ILOCK_EXCL;
/*
* Count the number of extended attribute blocks
@ -1810,8 +1813,8 @@ xfs_swap_extents(
goto out_trans_cancel;
}
xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
xfs_trans_ijoin(tp, tip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
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
@ -1940,8 +1943,8 @@ out:
return error;
out_unlock:
xfs_iunlock(ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
xfs_iunlock(tip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
xfs_iunlock(ip, lock_flags);
xfs_iunlock(tip, lock_flags);
goto out;
out_trans_cancel: