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xfs: fix mmap_sem/iolock inversion in xfs_free_eofblocks 

When xfs_free_eofblocks is called from ->release the VM might already
hold the mmap_sem, but in the write path we take the iolock before
taking the mmap_sem in the generic write code.

Switch xfs_free_eofblocks to only trylock the iolock if called from
->release and skip trimming the prellocated blocks in that case.
We'll still free them later on the final iput.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Christoph Hellwig 2009-10-19 04:03:46 +00:00 committed by Alex Elder
parent 848ce8f731
commit c56c9631cb
2 changed files with 26 additions and 15 deletions
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7
fs/xfs/xfs_rw.h
View File

@ -36,13 +36,6 @@ xfs_fsb_to_db(struct xfs_inode *ip, xfs_fsblock_t fsb)
XFS_FSB_TO_DADDR((ip)->i_mount, (fsb)));
}
/*
* Flags for xfs_free_eofblocks
*/
#define XFS_FREE_EOF_LOCK (1<<0)
#define XFS_FREE_EOF_NOLOCK (1<<1)
/*
* helper function to extract extent size hint from inode
*/

34
fs/xfs/xfs_vnodeops.c
View File

@ -708,6 +708,11 @@ xfs_fsync(
return error;
}
/*
* Flags for xfs_free_eofblocks
*/
#define XFS_FREE_EOF_TRYLOCK (1<<0)
/*
* This is called by xfs_inactive to free any blocks beyond eof
* when the link count isn't zero and by xfs_dm_punch_hole() when
@ -726,7 +731,6 @@ xfs_free_eofblocks(
xfs_filblks_t map_len;
int nimaps;
xfs_bmbt_irec_t imap;
int use_iolock = (flags & XFS_FREE_EOF_LOCK);
/*
* Figure out if there are any blocks beyond the end
@ -768,14 +772,19 @@ xfs_free_eofblocks(
* cache and we can't
* do that within a transaction.
*/
if (use_iolock)
if (flags & XFS_FREE_EOF_TRYLOCK) {
if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
xfs_trans_cancel(tp, 0);
return 0;
}
} else {
xfs_ilock(ip, XFS_IOLOCK_EXCL);
}
error = xfs_itruncate_start(ip, XFS_ITRUNC_DEFINITE,
ip->i_size);
if (error) {
xfs_trans_cancel(tp, 0);
if (use_iolock)
xfs_iunlock(ip, XFS_IOLOCK_EXCL);
xfs_iunlock(ip, XFS_IOLOCK_EXCL);
return error;
}
@ -812,8 +821,7 @@ xfs_free_eofblocks(
error = xfs_trans_commit(tp,
XFS_TRANS_RELEASE_LOG_RES);
}
xfs_iunlock(ip, (use_iolock ? (XFS_IOLOCK_EXCL|XFS_ILOCK_EXCL)
: XFS_ILOCK_EXCL));
xfs_iunlock(ip, XFS_IOLOCK_EXCL|XFS_ILOCK_EXCL);
}
return error;
}
@ -1113,7 +1121,17 @@ xfs_release(
(ip->i_df.if_flags & XFS_IFEXTENTS)) &&
(!(ip->i_d.di_flags &
(XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)))) {
error = xfs_free_eofblocks(mp, ip, XFS_FREE_EOF_LOCK);
/*
* If we can't get the iolock just skip truncating
* the blocks past EOF because we could deadlock
* with the mmap_sem otherwise. We'll get another
* chance to drop them once the last reference to
* the inode is dropped, so we'll never leak blocks
* permanently.
*/
error = xfs_free_eofblocks(mp, ip,
XFS_FREE_EOF_TRYLOCK);
if (error)
return error;
}
@ -1184,7 +1202,7 @@ xfs_inactive(
(!(ip->i_d.di_flags &
(XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)) ||
(ip->i_delayed_blks != 0)))) {
error = xfs_free_eofblocks(mp, ip, XFS_FREE_EOF_LOCK);
error = xfs_free_eofblocks(mp, ip, 0);
if (error)
return VN_INACTIVE_CACHE;
}