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.

Fixes: 93e72b3 ("squashfs: migrate from ll_rw_block usage to BIO")
Reported-by: Nicolas Prochazka <[email protected]>
Reported-by: Tomoatsu Shimada <[email protected]>
Signed-off-by: Phillip Lougher <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Guenter Roeck <[email protected]>
Cc: Philippe Liard <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Adrien Schildknecht <[email protected]>
Cc: Daniel Rosenberg <[email protected]>
Cc: <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

fs/squashfs/block.c

@@ -87,7 +87,11 @@ static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
 	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;