Messages in this thread | | | Date | Mon, 6 Jul 2015 10:21:52 -0700 | Subject | Re: [PATCH v5 10/11] block: remove bio_get_nr_vecs() | From | Ming Lin <> |
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On Mon, Jul 6, 2015 at 3:58 AM, Steven Whitehouse <swhiteho@redhat.com> wrote: > > Hi, > > > On 06/07/15 08:44, Ming Lin wrote: >> >> From: Kent Overstreet <kent.overstreet@gmail.com> >> >> We can always fill up the bio now, no need to estimate the possible >> size based on queue parameters. > > [snip] >> >> diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c >> index 2c1ae86..64d3116 100644 >> --- a/fs/gfs2/lops.c >> +++ b/fs/gfs2/lops.c >> @@ -261,18 +261,11 @@ void gfs2_log_flush_bio(struct gfs2_sbd *sdp, int rw) >> static struct bio *gfs2_log_alloc_bio(struct gfs2_sbd *sdp, u64 blkno) >> { >> struct super_block *sb = sdp->sd_vfs; >> - unsigned nrvecs = bio_get_nr_vecs(sb->s_bdev); >> struct bio *bio; >> BUG_ON(sdp->sd_log_bio); >> - while (1) { >> - bio = bio_alloc(GFP_NOIO, nrvecs); >> - if (likely(bio)) >> - break; >> - nrvecs = max(nrvecs/2, 1U); >> - } >> - >> + bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES); >> bio->bi_iter.bi_sector = blkno * (sb->s_blocksize >> 9); >> bio->bi_bdev = sb->s_bdev; >> bio->bi_end_io = gfs2_end_log_write; > > > When I wrote this loop I understood that bio_alloc(GFP_NOIO, x) was only guaranteed to be successful in the case x = 1, and that for x > 1, it might return NULL. Does this now mean that for x = BIO_MAX_PAGES it will be guaranteed to never return NULL in this case?
Yes, it's guaranteed.
https://lkml.org/lkml/2013/11/26/47
commit df2cb6daa4cbc
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