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[XFS] Fix race in xfs_write() between direct and buffered I/O with DMAPI

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The iolock is dropped and re-acquired around the call to XFS_SEND_NAMESP().
While the iolock is released the file can become cached.  We then
'goto retry' and - if we are doing direct I/O - mapping->nrpages may now be
non zero but need_i_mutex will be zero and we will hit the WARN_ON().

Since we have dropped the I/O lock then the file size may have also changed
so what we need to do here is 'goto start' like we do for the XFS_SEND_DATA()
DMAPI event.

We also need to update the filesize before releasing the iolock so that
needs to be done before the XFS_SEND_NAMESP event.  If we drop the iolock
before setting the filesize we could race with a truncate.

Reviewed-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
This commit is contained in:
Lachlan McIlroy 2008-12-24 14:07:32 +11:00
parent ad1ad968f4
commit 25051158bb
1 changed files with 12 additions and 15 deletions
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27
fs/xfs/linux-2.6/xfs_lrw.c
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@ -707,7 +707,6 @@ start:
} }
} }
retry:
/* We can write back this queue in page reclaim */ /* We can write back this queue in page reclaim */
current->backing_dev_info = mapping->backing_dev_info; current->backing_dev_info = mapping->backing_dev_info;
@ -763,6 +762,17 @@ retry:
if (ret == -EIOCBQUEUED && !(ioflags & IO_ISAIO)) if (ret == -EIOCBQUEUED && !(ioflags & IO_ISAIO))
ret = wait_on_sync_kiocb(iocb); ret = wait_on_sync_kiocb(iocb);
isize = i_size_read(inode);
if (unlikely(ret < 0 && ret != -EFAULT && *offset > isize))
*offset = isize;
if (*offset > xip->i_size) {
xfs_ilock(xip, XFS_ILOCK_EXCL);
if (*offset > xip->i_size)
xip->i_size = *offset;
xfs_iunlock(xip, XFS_ILOCK_EXCL);
}
if (ret == -ENOSPC && if (ret == -ENOSPC &&
DM_EVENT_ENABLED(xip, DM_EVENT_NOSPACE) && !(ioflags & IO_INVIS)) { DM_EVENT_ENABLED(xip, DM_EVENT_NOSPACE) && !(ioflags & IO_INVIS)) {
xfs_iunlock(xip, iolock); xfs_iunlock(xip, iolock);
@ -776,20 +786,7 @@ retry:
xfs_ilock(xip, iolock); xfs_ilock(xip, iolock);
if (error) if (error)
goto out_unlock_internal; goto out_unlock_internal;
pos = xip->i_size; goto start;
ret = 0;
goto retry;
}
isize = i_size_read(inode);
if (unlikely(ret < 0 && ret != -EFAULT && *offset > isize))
*offset = isize;
if (*offset > xip->i_size) {
xfs_ilock(xip, XFS_ILOCK_EXCL);
if (*offset > xip->i_size)
xip->i_size = *offset;
xfs_iunlock(xip, XFS_ILOCK_EXCL);
} }
error = -ret; error = -ret;