On Aug 14, 2015, at 2:15 PM, Jeff Moyer <jmoyer(a)redhat.com> wrote:
The dax code doesn't currently support misaligned partitions,
so disable O_DIRECT via dax until such time as that support
materializes.
Suggested-by: Boaz Harrosh <boaz(a)plexistor.com>
Signed-off-by: Jeff Moyer <jmoyer(a)redhat.com>
---
fs/block_dev.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 1982437..1170f8c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1241,6 +1241,13 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode,
int for_part)
goto out_clear;
}
bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
+ /*
+ * If the partition is not aligned on a page
+ * boundary, we can't do dax I/O to it.
+ */
+ if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512)) ||
+ (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
Maybe I'm missing something, but doesn't the second condition above
disable DAX for the case that the 1/2 patch is fixing (i.e. the last
sectors at the end of a non-PAGE_SIZE-multiple device)? It seems a
shame to disable DAX for the whole device because of the last sector.
+ bdev->bd_inode->i_flags &= ~S_DAX;
}
} else {
if (bdev->bd_contains == bdev) {
--
1.8.3.1
Cheers, Andreas