block: sanitize chunk_sectors for atomic write limits

Currently we just ensure that a non-zero value in chunk_sectors aligns
with any atomic write boundary, as the blk boundary functionality uses
both these values.

However it is also improper to have atomic write unit max > chunk_sectors
(for non-zero chunk_sectors), as this would lead to splitting of atomic
write bios (which is disallowed).

Sanitize atomic write unit max against chunk_sectors to avoid any
potential problems.

Fixes: d00eea9 ("block: Add extra checks in blk_validate_atomic_write_limits()")
Reviewed-by: Nilay Shroff <[email protected]>
Signed-off-by: John Garry <[email protected]>

Author: johnpgarry

block/blk-settings.c

@@ -181,6 +181,8 @@ static void blk_atomic_writes_update_limits(struct queue_limits *lim)
 static void blk_validate_atomic_write_limits(struct queue_limits *lim)
 {
 	unsigned int boundary_sectors;
+	unsigned int atomic_write_hw_max_sectors =
+			lim->atomic_write_hw_max >> SECTOR_SHIFT;
 
 	if (!(lim->features & BLK_FEAT_ATOMIC_WRITES))
 		goto unsupported;
@@ -202,6 +204,10 @@ static void blk_validate_atomic_write_limits(struct queue_limits *lim)
 			 lim->atomic_write_hw_max))
 		goto unsupported;
 
+	if (WARN_ON_ONCE(lim->chunk_sectors &&
+			atomic_write_hw_max_sectors > lim->chunk_sectors))
+		goto unsupported;
+
 	boundary_sectors = lim->atomic_write_hw_boundary >> SECTOR_SHIFT;
 
 	if (boundary_sectors) {