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| author | David Chinner <dgc@sgi.com> | 2006-03-22 12:47:15 +1100 |
|---|---|---|
| committer | Nathan Scott <nathans@sgi.com> | 2006-03-22 12:47:15 +1100 |
| commit | 38e2299a641d93d029eb559e096648ab75a22be2 (patch) | |
| tree | 3aa1afbd899c668ff6f50daa302533a219f8c8c3 /fs/xfs | |
| parent | 9fa8046f50bcb88ab9183ee1f22de5adc42bf92a (diff) | |
| download | lwn-38e2299a641d93d029eb559e096648ab75a22be2.tar.gz lwn-38e2299a641d93d029eb559e096648ab75a22be2.zip | |
[XFS] Explain the race closed by the addition of vn_iowait() to the start
of xfs_itruncate_start().
SGI-PV: 947420
SGI-Modid: xfs-linux-melb:xfs-kern:25527a
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
Diffstat (limited to 'fs/xfs')
| -rw-r--r-- | fs/xfs/xfs_inode.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 8d2b36879f06..88a517fad07b 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1393,6 +1393,16 @@ xfs_itrunc_trace( * calling into the buffer/page cache code and we can't hold the * inode lock when we do so. * + * We need to wait for any direct I/Os in flight to complete before we + * proceed with the truncate. This is needed to prevent the extents + * being read or written by the direct I/Os from being removed while the + * I/O is in flight as there is no other method of synchronising + * direct I/O with the truncate operation. Also, because we hold + * the IOLOCK in exclusive mode, we prevent new direct I/Os from being + * started until the truncate completes and drops the lock. Essentially, + * the vn_iowait() call forms an I/O barrier that provides strict ordering + * between direct I/Os and the truncate operation. + * * The flags parameter can have either the value XFS_ITRUNC_DEFINITE * or XFS_ITRUNC_MAYBE. The XFS_ITRUNC_MAYBE value should be used * in the case that the caller is locking things out of order and |