From: Phillip Lougher phillip@squashfs.org.uk Subject: squashfs: avoid bio_alloc() failure with 1Mbyte blocks

This is a regression introduced by the patch "migrate from ll_rw_block usage to BIO".

Bio_alloc() is limited to 256 pages (1 Mbyte). This can cause a failure when reading 1 Mbyte block filesystems. The problem is a datablock can be fully (or almost uncompressed), requiring 256 pages, but, because blocks are not aligned to page boundaries, it may require 257 pages to read.

Bio_kmalloc() can handle 1024 pages, and so use this for the edge condition.

Link: http://lkml.kernel.org/r/20200815035637.15319-1-phillip@squashfs.org.uk Fixes: 93e72b3c612a ("squashfs: migrate from ll_rw_block usage to BIO") Signed-off-by: Phillip Lougher phillip@squashfs.org.uk Reported-by: Nicolas Prochazka nicolas.prochazka@gmail.com Reported-by: Tomoatsu Shimada shimada@walbrix.com Reviewed-by: Guenter Roeck groeck@chromium.org Cc: Philippe Liard pliard@google.com Cc: Christoph Hellwig hch@lst.de Cc: Adrien Schildknecht adrien+dev@schischi.me Cc: Daniel Rosenberg drosen@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/squashfs/block.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/squashfs/block.c~squashfs-avoid-bio_alloc-failure-with-1mbyte-blocks +++ a/fs/squashfs/block.c @@ -87,7 +87,11 @@ static int squashfs_bio_read(struct supe int error, i; struct bio *bio;

- bio = bio_alloc(GFP_NOIO, page_count); + if (page_count <= BIO_MAX_PAGES) + bio = bio_alloc(GFP_NOIO, page_count); + else + bio = bio_kmalloc(GFP_NOIO, page_count); + if (!bio) return -ENOMEM;

_