[PATCH] loop: set physical block size to logical block size

[PATCH] loop: set physical block size to logical block size

[Omar Sandoval]

From: Omar Sandoval <osandov@fb.com>

Commit 6c6b6f28b333 ("loop: set physical block size to PAGE_SIZE")
caused mkfs.xfs to barf on ppc64 [1]. Always using PAGE_SIZE as the
physical block size still makes the most sense semantically, but let's
just lie and always set it to the same value as the logical block size
(same goes for io_min). In the future we might want to at least bump up
io_min to PAGE_SIZE but I'm sick of these stupid changes so let's play
it safe.

1: https://marc.info/?l=linux-xfs&m=150459024723753&w=2

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 drivers/block/loop.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 78c47c4b584d..85de67334695 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1036,6 +1036,8 @@ static int loop_clr_fd(struct loop_device *lo)
 	memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
 	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
 	blk_queue_logical_block_size(lo->lo_queue, 512);
+	blk_queue_physical_block_size(lo->lo_queue, 512);
+	blk_queue_io_min(lo->lo_queue, 512);
 	if (bdev) {
 		bdput(bdev);
 		invalidate_bdev(bdev);
@@ -1330,6 +1332,8 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 	blk_mq_freeze_queue(lo->lo_queue);
 
 	blk_queue_logical_block_size(lo->lo_queue, arg);
+	blk_queue_physical_block_size(lo->lo_queue, arg);
+	blk_queue_io_min(lo->lo_queue, arg);
 	loop_update_dio(lo);
 
 	blk_mq_unfreeze_queue(lo->lo_queue);
@@ -1777,8 +1781,6 @@ static int loop_add(struct loop_device **l, int i)
 	}
 	lo->lo_queue->queuedata = lo;
 
-	blk_queue_physical_block_size(lo->lo_queue, PAGE_SIZE);
-
 	blk_queue_max_hw_sectors(lo->lo_queue, BLK_DEF_MAX_SECTORS);
 
 	/*
-- 
2.14.1

Re: [PATCH] loop: set physical block size to logical block size

[Chandan Rajendra]

On Wednesday, September 6, 2017 2:54:47 AM IST Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Commit 6c6b6f28b333 ("loop: set physical block size to PAGE_SIZE")
> caused mkfs.xfs to barf on ppc64 [1]. Always using PAGE_SIZE as the
> physical block size still makes the most sense semantically, but let's
> just lie and always set it to the same value as the logical block size
> (same goes for io_min). In the future we might want to at least bump up
> io_min to PAGE_SIZE but I'm sick of these stupid changes so let's play
> it safe.
> 

With this patch applied, On ppc64 I get,

# blockdev --getss /dev/loop0    
512                                                           
# blockdev --getpbsz /dev/loop0  
512                                                           

i.e. we are back to what was being reported before commit 6c6b6f28b333 
was applied.

I also executed xfstests on xfs filesystems with 4k and 32k block sizes and 
did not notice any regressions.

Tested-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>

-- 
chandan