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xfs: improve the IOMAP_NOWAIT check for COW inodes

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Only bail out once we know that a COW allocation is actually required,
similar to how we handle normal data fork allocations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2019-10-19 09:09:47 -07:00 committed by Darrick J. Wong
parent 5c5b6f7585
commit 1e190f8e80
1 changed files with 5 additions and 18 deletions
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23
fs/xfs/xfs_iomap.c
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@ -693,15 +693,8 @@ xfs_ilock_for_iomap(
* COW writes may allocate delalloc space or convert unwritten COW
* extents, so we need to make sure to take the lock exclusively here.
*/
if (xfs_is_cow_inode(ip) && is_write) {
/*
* FIXME: It could still overwrite on unshared extents and not
* need allocation.
*/
if (flags & IOMAP_NOWAIT)
return -EAGAIN;
if (xfs_is_cow_inode(ip) && is_write)
mode = XFS_ILOCK_EXCL;
}
/*
* Extents not yet cached requires exclusive access, don't block. This
@ -769,12 +762,6 @@ xfs_direct_write_iomap_begin(
if (offset + length > i_size_read(inode))
iomap_flags |= IOMAP_F_DIRTY;
/*
* Lock the inode in the manner required for the specified operation and
* check for as many conditions that would result in blocking as
* possible. This removes most of the non-blocking checks from the
* mapping code below.
*/
error = xfs_ilock_for_iomap(ip, flags, &lockmode);
if (error)
return error;
@ -784,11 +771,11 @@ xfs_direct_write_iomap_begin(
if (error)
goto out_unlock;
/*
* Break shared extents if necessary. Checks for non-blocking IO have
* been done up front, so we don't need to do them here.
*/
if (imap_needs_cow(ip, flags, &imap, nimaps)) {
error = -EAGAIN;
if (flags & IOMAP_NOWAIT)
goto out_unlock;
/* may drop and re-acquire the ilock */
error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,
&lockmode, flags & IOMAP_DIRECT);