linux-ext4 - [PATCH v5 11/12] ext4: reorder map->m_flags checks in ext4_set

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Message-ID: <a19bf499c10fc3d668ffee22519f3a8f62e8e307.1571647180.git.mbobrowski@mbobrowski.org>
Date:   Mon, 21 Oct 2019 20:20:29 +1100
From:   Matthew Bobrowski <mbobrowski@...browski.org>
To:     tytso@....edu, jack@...e.cz, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        hch@...radead.org, david@...morbit.com, darrick.wong@...cle.com
Subject: [PATCH v5 11/12] ext4: reorder map->m_flags checks in
 ext4_set_iomap()

For the direct I/O iomap write changes that follow in this patch
series, we need to accommodate for the case where the block mapping
flags passed to ext4_map_blocks() result in map->m_flags having both
EXT4_MAP_MAPPED and EXT4_MAP_UNWRITTEN bits set. In order for
allocated unwritten extents to be converted correctly in the
->end_io() handler, the iomap->type must be set to IOMAP_UNWRITTEN for
cases where map->m_flags has EXT4_MAP_UNWRITTEN set. Hence the reason
why we reshuffle the conditional statement in this patch.

This change is a no-op for DAX as the block mapping flags passed to
ext4_map_blocks() when the inode IS_DAX never results in both
EXT4_MAP_MAPPED and EXT4_MAP_UNWRITTEN being set at once.

Signed-off-by: Matthew Bobrowski <mbobrowski@...browski.org>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: Ritesh Harjani <riteshh@...ux.ibm.com>
---
 fs/ext4/inode.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a37112efe3fb..70ddcb9c2c1c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3428,10 +3428,19 @@ static void ext4_set_iomap(struct inode *inode, struct iomap *iomap,
 	iomap->length = (u64) map->m_len << blkbits;
 
 	if (map->m_flags & (EXT4_MAP_MAPPED | EXT4_MAP_UNWRITTEN)) {
-		if (map->m_flags & EXT4_MAP_MAPPED)
-			iomap->type = IOMAP_MAPPED;
-		else if (map->m_flags & EXT4_MAP_UNWRITTEN)
+		/*
+		 * Flags passed into ext4_map_blocks() for direct I/O writes
+		 * can result in map->m_flags having both EXT4_MAP_MAPPED and
+		 * EXT4_MAP_UNWRITTEN bits set. In order for any allocated
+		 * extents to be converted to written extents correctly in the
+		 * ->end_io() handler, we need to ensure that the iomap->type
+		 *  is set appropriately. Hence the reason why we need to check
+		 *  whether EXT4_MAP_UNWRITTEN is set first.
+		 */
+		if (map->m_flags & EXT4_MAP_UNWRITTEN)
 			iomap->type = IOMAP_UNWRITTEN;
+		else if (map->m_flags & EXT4_MAP_MAPPED)
+			iomap->type = IOMAP_MAPPED;
 		iomap->addr = (u64) map->m_pblk << blkbits;
 	} else {
 		iomap->type = IOMAP_HOLE;
-- 
2.20.1

--<M>--