The loop driver assumes that if the passed in fd is opened with
O_DIRECT, the caller wants to use direct I/O on the loop device.
However, if the underlying block device has a different block size than
the loop block queue, direct I/O can't be enabled. Instead of requiring
userspace to manually change the blocksize and re-enable direct I/O,
just change the queue block sizes to match, as well as the io_min size.
Signed-off-by: Martijn Coenen <maco@xxxxxxxxxxx>
---
v2 changes:
- Fixed commit message to say the block size must match the underlying
block device, not the underlying filesystem.
- Also set physical blocksize and minimal io size correspondingly.
drivers/block/loop.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ab7ca5989097a..b547182037af2 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -994,6 +994,16 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
blk_queue_write_cache(lo->lo_queue, true, false);
+ if (io_is_direct(lo->lo_backing_file) && inode->i_sb->s_bdev) {
+ /* In case of direct I/O, match underlying block size */
+ unsigned short bsize = bdev_logical_block_size(
+ inode->i_sb->s_bdev);
+
+ blk_queue_logical_block_size(lo->lo_queue, bsize);
+ blk_queue_physical_block_size(lo->lo_queue, bsize);
+ blk_queue_io_min(lo->lo_queue, bsize);
+ }
+
loop_update_rotational(lo);
loop_update_dio(lo);
set_capacity(lo->lo_disk, size);
--
2.23.0.187.g17f5b7556c-goog
