block: ensure that bio_add_page() always accepts a page for an empty bio

With commit 762380a added support for chunk sizes and no merging across them, it broke the rule of always allowing adding of a single page to an empty bio. So relax the restriction a bit to allow for that, similarly to what we have always done. This fixes a crash with mkfs.xfs and 512b sector sizes on NVMe. Reported-by: Keith Busch <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
berg · Jun 10, 2014 · 58a4915 · 58a4915
1 parent 2b8393b
commit 58a4915
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/block/bio.c b/block/bio.c
@@ -849,8 +849,13 @@ int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
 		 unsigned int offset)
 {
 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+	unsigned int max_sectors;
 
-	return __bio_add_page(q, bio, page, len, offset, blk_max_size_offset(q, bio->bi_iter.bi_sector));
+	max_sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
+	if ((max_sectors < (len >> 9)) && !bio->bi_iter.bi_size)
+		max_sectors = len >> 9;
+
+	return __bio_add_page(q, bio, page, len, offset, max_sectors);
 }
 EXPORT_SYMBOL(bio_add_page);
 

diff --git a/block/blk-settings.c b/block/blk-settings.c
@@ -285,7 +285,10 @@ EXPORT_SYMBOL(blk_queue_max_hw_sectors);
  * Description:
  *    If a driver doesn't want IOs to cross a given chunk size, it can set
  *    this limit and prevent merging across chunks. Note that the chunk size
- *    must currently be a power-of-2 in sectors.
+ *    must currently be a power-of-2 in sectors. Also note that the block
+ *    layer must accept a page worth of data at any offset. So if the
+ *    crossing of chunks is a hard limitation in the driver, it must still be
+ *    prepared to split single page bios.
  **/
 void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors)
 {