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ext4: iomap that extends beyond EOF should be marked dirty 

This patch addresses what Dave Chinner had discovered and fixed within
commit: 7684e2c438. 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>
Link: https://lore.kernel.org/r/8b43ee9ee94bee5328da56ba0909b7d2229ef150.1572949325.git.mbobrowski@mbobrowski.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Matthew Bobrowski 2019-11-05 22:59:37 +11:00 committed by Theodore Ts'o
parent 548feebec7
commit 2e9b51d782
1 changed files with 7 additions and 1 deletions
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8
fs/ext4/inode.c
View File

@ -3565,8 +3565,14 @@ 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;