Patch "ext4: iomap that extends beyond EOF should be marked dirty" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ext4: iomap that extends beyond EOF should be marked dirty

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-iomap-that-extends-beyond-eof-should-be-marked-.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9a9e106c3c12f046afcba89be3188601be682a93
Author: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx>
Date:   Tue Nov 5 22:59:37 2019 +1100

    ext4: iomap that extends beyond EOF should be marked dirty
    
    [ Upstream commit 2e9b51d78229d5145725a481bb5464ebc0a3f9b2 ]
    
    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@xxxxxxxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/8b43ee9ee94bee5328da56ba0909b7d2229ef150.1572949325.git.mbobrowski@xxxxxxxxxxxxxx
    Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 00d0c4b8fa30..950e3dcff7b0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3544,8 +3544,14 @@ retry:
 			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;