This patch is effectively addressed what Dave Chinner had found and
fixed within this commit: 8a23414ee345. Justification for needing this
modification has been provided below:
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>
---
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 158eea9a1944..0dd29ae5cc8c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3412,8 +3412,14 @@ static void ext4_set_iomap(struct inode *inode, struct iomap *iomap,
{
u8 blkbits = inode->i_blkbits;
+ /*
+ * 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;
if (map->m_flags & EXT4_MAP_NEW)
--
2.20.1
--<M>--
