[PATCH 5.8 017/148] squashfs: avoid bio_alloc() failure with 1Mbyte blocks

[Greg Kroah-Hartman]

From: Phillip Lougher <phillip@xxxxxxxxxxxxxxx>

commit f26044c83e6e473a61917f5db411d1417327d425 upstream.

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.

Fixes: 93e72b3c612a ("squashfs: migrate from ll_rw_block usage to BIO")
Reported-by: Nicolas Prochazka <nicolas.prochazka@xxxxxxxxx>
Reported-by: Tomoatsu Shimada <shimada@xxxxxxxxxxx>
Signed-off-by: Phillip Lougher <phillip@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <groeck@xxxxxxxxxxxx>
Cc: Philippe Liard <pliard@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Adrien Schildknecht <adrien+dev@xxxxxxxxxxx>
Cc: Daniel Rosenberg <drosen@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20200815035637.15319-1-phillip@xxxxxxxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/fs/squashfs/block.c
+++ b/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;