[PATCH v4 2/6] block: sanitize chunk_sectors for atomic write limits

[John Garry]

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: d00eea91deaf3 ("block: Add extra checks in 
blk_validate_atomic_write_limits()")
Reviewed-by: Nilay Shroff <ni...@linux.ibm.com>
Signed-off-by: John Garry <john.g.ga...@oracle.com>
---
 block/blk-settings.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index a000daafbfb4..761c6ccf5af7 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -181,6 +181,7 @@ 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 long chunk_bytes;
 
        if (!(lim->features & BLK_FEAT_ATOMIC_WRITES))
                goto unsupported;
@@ -202,6 +203,13 @@ static void blk_validate_atomic_write_limits(struct 
queue_limits *lim)
                         lim->atomic_write_hw_max))
                goto unsupported;
 
+       chunk_bytes = lim->chunk_sectors << SECTOR_SHIFT;
+       if (chunk_bytes) {
+               if (WARN_ON_ONCE(lim->atomic_write_hw_unit_max >
+                       chunk_bytes))
+                       goto unsupported;
+       }
+
        boundary_sectors = lim->atomic_write_hw_boundary >> SECTOR_SHIFT;
 
        if (boundary_sectors) {
-- 
2.43.5