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Date: Fri, 14 Aug 2020 21:30:33 -0700 From: Guenter Roeck <groeck@...gle.com> To: Phillip Lougher <phillip@...ashfs.org.uk> Cc: linux-kernel <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, Philippe Liard <pliard@...gle.com>, hch@....de, adrien+dev@...ischi.me, Guenter Roeck <groeck@...omium.org>, Daniel Rosenberg <drosen@...gle.com>, Nicolas Prochazka <nicolas.prochazka@...il.com>, Tomoatsu Shimada <shimada@...brix.com> Subject: Re: [PATCH] squashfs: avoid bio_alloc() failure with 1Mbyte blocks On Fri, Aug 14, 2020 at 8:57 PM Phillip Lougher <phillip@...ashfs.org.uk> wrote: > > This is a regression introduced by the "migrate from ll_rw_block usage > to BIO" patch. > > 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. > > Reported-by: Nicolas Prochazka <nicolas.prochazka@...il.com> > Reported-by: Tomoatsu Shimada <shimada@...brix.com> > Signed-off-by: Phillip Lougher <phillip@...ashfs.org.uk> Fixes: 93e72b3c612a ("squashfs: migrate from ll_rw_block usage to BIO") Reviewed-by: Guenter Roeck <groeck@...omium.org> > --- > fs/squashfs/block.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c > index 76bb1c846845..8a19773b5a0b 100644 > --- a/fs/squashfs/block.c > +++ b/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; > > -- > 2.20.1 >
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