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From: Matthew Bobrowski <mbobrowski@mbobrowski.org>
To: tytso@mit.edu, jack@suse.cz, adilger.kernel@dilger.ca
Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	riteshh@linux.ibm.com
Subject: [PATCH v7 03/11] ext4: iomap that extends beyond EOF should be marked dirty
Date: Tue, 5 Nov 2019 22:59:37 +1100
Message-ID: <8b43ee9ee94bee5328da56ba0909b7d2229ef150.1572949325.git.mbobrowski@mbobrowski.org> (raw)
In-Reply-To: <cover.1572949325.git.mbobrowski@mbobrowski.org>

This patch addresses what Dave Chinner had discovered and fixed within
commit: 7684e2c4384d. This changes does not have any user visible
impact for ext4 as none of the current users of ext4_iomap_begin()
that extend files depend on IOMAP_F_DIRTY.

When doing a direct IO that spans the current EOF, and there are
written blocks beyond EOF that extend beyond the current write, the
only metadata update that needs to be done is a file size extension.

However, we don't mark such iomaps as IOMAP_F_DIRTY to indicate that
there is IO completion metadata updates required, and hence we may
fail to correctly sync file size extensions made in IO completion when
O_DSYNC writes are being used and the hardware supports FUA.

Hence when setting IOMAP_F_DIRTY, we need to also take into account
whether the iomap spans the current EOF. If it does, then we need to
mark it dirty so that IO completion will call generic_write_sync() to
flush the inode size update to stable storage correctly.

Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
---
 fs/ext4/inode.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f33fa86fff67..b422d9b8c0bd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3565,8 +3565,14 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 			return ret;
 	}
 
+	/*
+	 * Writes that span EOF might trigger an I/O size update on completion,
+	 * so consider them to be dirty for the purposes of O_DSYNC, even if
+	 * there is no other metadata changes being made or are pending here.
+	 */
 	iomap->flags = 0;
-	if (ext4_inode_datasync_dirty(inode))
+	if (ext4_inode_datasync_dirty(inode) ||
+	    offset + length > i_size_read(inode))
 		iomap->flags |= IOMAP_F_DIRTY;
 	iomap->bdev = inode->i_sb->s_bdev;
 	iomap->dax_dev = sbi->s_daxdev;
-- 
2.20.1


  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-05 11:58 [PATCH v7 00/11] ext4: port direct I/O to iomap infrastructure Matthew Bobrowski
2019-11-05 11:58 ` [PATCH v7 01/11] ext4: reorder map.m_flags checks within ext4_iomap_begin() Matthew Bobrowski
2019-11-05 11:59 ` [PATCH v7 02/11] ext4: update direct I/O read lock pattern for IOCB_NOWAIT Matthew Bobrowski
2019-11-05 11:59 ` Matthew Bobrowski [this message]
2019-11-05 11:59 ` [PATCH v7 04/11] ext4: move set iomap routines into a separate helper ext4_set_iomap() Matthew Bobrowski
2019-11-05 12:00 ` [PATCH v7 05/11] ext4: split IOMAP_WRITE branch in ext4_iomap_begin() into helper Matthew Bobrowski
2019-11-05 12:01 ` [PATCH v7 07/11] ext4: introduce direct I/O read using iomap infrastructure Matthew Bobrowski
2019-11-05 12:01 ` [PATCH v7 08/11] ext4: move inode extension/truncate code out from ->iomap_end() callback Matthew Bobrowski
2019-11-05 15:49   ` Darrick J. Wong
2019-11-05 21:10     ` Matthew Bobrowski
2019-11-05 12:02 ` [PATCH v7 09/11] ext4: move inode extension check out from ext4_iomap_alloc() Matthew Bobrowski
2019-11-05 12:02 ` [PATCH v7 10/11] ext4: update ext4_sync_file() to not use __generic_file_fsync() Matthew Bobrowski
2019-11-05 12:02 ` [PATCH v7 11/11] ext4: introduce direct I/O write using iomap infrastructure Matthew Bobrowski
2019-11-05 13:59   ` Jan Kara
2019-11-05 20:32     ` Matthew Bobrowski
2019-11-05 20:53       ` Theodore Y. Ts'o
2019-11-05 21:00         ` Matthew Bobrowski
2019-11-06  0:59           ` Theodore Y. Ts'o
2019-11-05 16:28   ` Theodore Y. Ts'o
2019-11-05 20:57     ` Matthew Bobrowski
2019-11-05 12:03 ` [PATCH v7 06/11] ext4: introduce new callback for IOMAP_REPORT Matthew Bobrowski
2019-11-05 15:43   ` Darrick J. Wong

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