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xfs: reorder zeroing and flushing sequence in truncate

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Currently zeroing out blocks and waiting for writeout is a bit of a mess in
truncate.  This patch gives it a clear order in preparation for the iomap
path:

 (1) we first wait for any direct I/O to complete to prevent any races
     for it
 (2) we then perform the actual zeroing, and only use the truncate_page
     helpers for truncating down.  The truncate up case already is
     handled by the separate call to xfs_zero_eof.
 (3) only then we write back dirty data, as zeroing block may cause
     dirty pages when using either xfs_zero_eof or the new iomap
     infrastructure.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig 2016-06-21 09:52:47 +10:00 committed by Dave Chinner
parent 3b3dce0527
commit f0c6bcba74
1 changed files with 19 additions and 14 deletions
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33
fs/xfs/xfs_iops.c
View file

@ -800,21 +800,36 @@ xfs_setattr_size(
if (error)
return error;
/*
* Wait for all direct I/O to complete.
*/
inode_dio_wait(inode);
/*
* File data changes must be complete before we start the transaction to
* modify the inode. This needs to be done before joining the inode to
* the transaction because the inode cannot be unlocked once it is a
* part of the transaction.
*
* Start with zeroing any data block beyond EOF that we may expose on
* file extension.
* Start with zeroing any data beyond EOF that we may expose on file
* extension, or zeroing out the rest of the block on a downward
* truncate.
*/
if (newsize > oldsize) {
error = xfs_zero_eof(ip, newsize, oldsize, &did_zeroing);
if (error)
return error;
} else {
if (IS_DAX(inode)) {
error = dax_truncate_page(inode, newsize,
xfs_get_blocks_direct);
} else {
error = block_truncate_page(inode->i_mapping, newsize,
xfs_get_blocks);
}
}
if (error)
return error;
/*
* We are going to log the inode size change in this transaction so
* any previous writes that are beyond the on disk EOF and the new
@ -831,9 +846,6 @@ xfs_setattr_size(
return error;
}
/* Now wait for all direct I/O to complete. */
inode_dio_wait(inode);
/*
* We've already locked out new page faults, so now we can safely remove
* pages from the page cache knowing they won't get refaulted until we
@ -851,13 +863,6 @@ xfs_setattr_size(
* to hope that the caller sees ENOMEM and retries the truncate
* operation.
*/
if (IS_DAX(inode))
error = dax_truncate_page(inode, newsize, xfs_get_blocks_direct);
else
error = block_truncate_page(inode->i_mapping, newsize,
xfs_get_blocks);
if (error)
return error;
truncate_setsize(inode, newsize);
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);