From: Matthew Bobrowski mbobrowski@mbobrowski.org
[ 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@mbobrowski.org Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Ritesh Harjani riteshh@linux.ibm.com Link: https://lore.kernel.org/r/8b43ee9ee94bee5328da56ba0909b7d2229ef150.157294932... Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Sasha Levin sashal@kernel.org --- 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 00d25a0643913..8eaf7a581be65 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3535,8 +3535,14 @@ 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;