dm-bufio: align write boundary on physical block size

commit d0ac06ae53be0cdb61f5fe6b62d25d3317c51657 upstream.

There may be devices with physical block size larger than 4k.

If dm-bufio sends I/O that is not aligned on physical block size,
performance is degraded.

The 4k minimum alignment limit is there because some SSDs report logical
and physical block size 512 despite having 4k internally - so dm-bufio
shouldn't send I/Os not aligned on 4k boundary, because they perform
badly (the SSD does read-modify-write for them).

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index aaa21fe295f2d7a96362000724438b0aef92ec1c..c3252fdc75fd4d1115c489937d1b3e9492f5fe0d 100644 (file)
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -1375,7 +1375,7 @@ static void submit_io(struct dm_buffer *b, enum req_op op, unsigned short ioprio
 {
        unsigned int n_sectors;
        sector_t sector;
-       unsigned int offset, end;
+       unsigned int offset, end, align;
 
        b->end_io = end_io;
 
@@ -1389,9 +1389,11 @@ static void submit_io(struct dm_buffer *b, enum req_op op, unsigned short ioprio
                        b->c->write_callback(b);
                offset = b->write_start;
                end = b->write_end;
-               offset &= -DM_BUFIO_WRITE_ALIGN;
-               end += DM_BUFIO_WRITE_ALIGN - 1;
-               end &= -DM_BUFIO_WRITE_ALIGN;
+               align = max(DM_BUFIO_WRITE_ALIGN,
+                       bdev_physical_block_size(b->c->bdev));
+               offset &= -align;
+               end += align - 1;
+               end &= -align;
                if (unlikely(end > b->c->block_size))
                        end = b->c->block_size;