On Mon, Jul 6, 2015 at 3:58 AM, Steven Whitehouse <swhit...@redhat.com> wrote:
>
> Hi,
>
>
> On 06/07/15 08:44, Ming Lin wrote:
>>
>> From: Kent Overstreet <kent.overstr...@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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