lkml.org 
[lkml]   [2011]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: fs/direct-io.c: don't try to allocate more than BIO_MAX_PAGES in a bio
Date
David Dillow <dillowda@ornl.gov> writes:

> When using devices that support max_segments > BIO_MAX_PAGES (256),
> direct IO tries to allocate a bio with more pages than allowed, which
> leads to an oops in dio_bio_alloc(). Clamp that request to the supported
> maximum.
>
> Signed-off-by: David Dillow <dillowda@ornl.gov>
> --
> dio_bio_alloc() doesn't check the result of bio_alloc(), so it
> dereferences a NULL pointer. bio_alloc(GFP_KERNEL, ...) doesn't fail
> unless it gets called for an invalid number of pages, so it seems a bit
> like overkill to check for failure in dio_bio_alloc(), though it would
> have saved me some time tracking this down.

We should always be checking return values. Mind respinning the patch
to include that?

> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 85882f6..9eb0553 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -583,6 +583,7 @@ static int dio_new_bio(struct dio *dio, sector_t start_sector)
> goto out;
> sector = start_sector << (dio->blkbits - 9);
> nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
> + nr_pages = min(nr_pages, BIO_MAX_PAGES);

This looks fine. Thanks for tracking it down!

Cheers,
Jeff


\
 
 \ /
  Last update: 2011-01-14 15:47    [W:0.053 / U:1.244 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site