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From: Christoph Hellwig <hch@lst.de>
To: Goldwyn Rodrigues <rgoldwyn@suse.com>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH 19/19] xfs: improve the IOMAP_NOWAIT check for COW inodes
Date: Mon,  9 Sep 2019 20:27:22 +0200
Message-ID: <20190909182722.16783-20-hch@lst.de> (raw)
In-Reply-To: <20190909182722.16783-1-hch@lst.de>

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>
---
 fs/xfs/xfs_iomap.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index e4e79aa5b695..9e1b4b94acac 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -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
@@ -760,12 +753,6 @@ xfs_direct_write_iomap_begin(
 	if (XFS_FORCED_SHUTDOWN(mp))
 		return -EIO;
 
-	/*
-	 * 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;
@@ -775,11 +762,11 @@ 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, &imap, flags, 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);
-- 
2.20.1


  parent reply index

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09 18:27 iomap and xfs COW cleanups Christoph Hellwig
2019-09-09 18:27 ` [PATCH 01/19] iomap: better document the IOMAP_F_* flags Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-16 18:08   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 02/19] iomap: remove the unused iomap argument to __iomap_write_end Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-16 18:10   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 03/19] iomap: always use AOP_FLAG_NOFS in iomap_write_begin Christoph Hellwig
2019-09-16 18:11   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 04/19] iomap: ignore non-shared or non-data blocks in xfs_file_dirty Christoph Hellwig
2019-09-16 18:12   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 05/19] iomap: move the zeroing case out of iomap_read_page_sync Christoph Hellwig
2019-09-16 18:17   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 06/19] iomap: use write_begin to read pages to unshare Christoph Hellwig
2019-09-16 18:34   ` Darrick J. Wong
2019-09-30 11:07     ` Christoph Hellwig
2019-10-08 15:12       ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 07/19] iomap: use a srcmap for a read-modify-write I/O Christoph Hellwig
2019-09-10 12:48   ` Goldwyn Rodrigues
2019-09-10 14:39     ` hch
2019-09-16 17:57       ` Darrick J. Wong
2019-09-16 18:42   ` Darrick J. Wong
2019-09-18 18:15     ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 08/19] xfs: also call xfs_file_iomap_end_delalloc for zeroing operations Christoph Hellwig
2019-09-18 17:09   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 09/19] xfs: remove xfs_reflink_dirty_extents Christoph Hellwig
2019-09-18 17:17   ` Darrick J. Wong
2019-09-18 17:25     ` Christoph Hellwig
2019-09-18 17:31       ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 10/19] xfs: pass two imaps to xfs_reflink_allocate_cow Christoph Hellwig
2019-09-18 17:26   ` Darrick J. Wong
2019-09-30 11:10     ` Christoph Hellwig
2019-09-09 18:27 ` [PATCH 11/19] xfs: refactor xfs_file_iomap_begin_delay Christoph Hellwig
2019-09-18 17:30   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 12/19] xfs: fill out the srcmap in iomap_begin Christoph Hellwig
2019-09-18 17:52   ` Darrick J. Wong
2019-10-01  6:26     ` Christoph Hellwig
2019-09-09 18:27 ` [PATCH 13/19] xfs: factor out a helper to calculate the end_fsb Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-18 17:55   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 14/19] xfs: split out a new set of read-only iomap ops Christoph Hellwig
2019-09-18 17:56   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 15/19] xfs: move xfs_file_iomap_begin_delay around Christoph Hellwig
2019-09-18 17:59   ` Darrick J. Wong
2019-09-30 11:14     ` Christoph Hellwig
2019-09-09 18:27 ` [PATCH 16/19] xfs: split the iomap ops for buffered vs direct writes Christoph Hellwig
2019-09-18 18:00   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 17/19] xfs: rename the whichfork variable in xfs_buffered_write_iomap_begin Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-18 18:00   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 18/19] xfs: cleanup xfs_iomap_write_unwritten Christoph Hellwig
2019-09-18 18:06   ` Darrick J. Wong
2019-09-09 18:27 ` Christoph Hellwig [this message]
2019-09-18 18:09   ` [PATCH 19/19] xfs: improve the IOMAP_NOWAIT check for COW inodes Darrick J. Wong

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