Commit f908ee94 authored May 11, 2012 by Bernd Schubert Committed by Jens Axboe May 11, 2012

bio allocation failure due to bio_get_nr_vecs()



The number of bio_get_nr_vecs() is passed down via bio_alloc() to
bvec_alloc_bs(), which fails the bio allocation if
nr_iovecs > BIO_MAX_PAGES. For the underlying caller this causes an
unexpected bio allocation failure.
Limiting to queue_max_segments() is not sufficient, as max_segments
also might be very large.

bvec_alloc_bs(gfp_mask, nr_iovecs, ) => NULL when nr_iovecs  > BIO_MAX_PAGES
bio_alloc_bioset(gfp_mask, nr_iovecs, ...)
bio_alloc(GFP_NOIO, nvecs)
xfs_alloc_ioend_bio()

Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 080399aa

fs/bio.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -505,9 +505,14 @@ EXPORT_SYMBOL(bio_clone);
		int bio_get_nr_vecs(struct block_device *bdev)
		{
		struct request_queue *q = bdev_get_queue(bdev);
		return min_t(unsigned,
		int nr_pages;

		nr_pages = min_t(unsigned,
		queue_max_segments(q),
		queue_max_sectors(q) / (PAGE_SIZE >> 9) + 1);

		return min_t(unsigned, nr_pages, BIO_MAX_PAGES);

		}
		EXPORT_SYMBOL(bio_get_nr_vecs);

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