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author | Jens Axboe <jens.axboe@oracle.com> | 2009-04-15 09:00:07 +0200 |
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committer | Jens Axboe <jens.axboe@oracle.com> | 2009-04-15 12:10:12 +0200 |
commit | 86c824b9434e764d01489688e4e38aee43b93fcf (patch) | |
tree | 0aa776b6fb5af04e9392c3f49842eeee97a5bd74 /fs/bio.c | |
parent | 61e0d47c33cc371f725bcda4a47ae0efe652dba8 (diff) | |
download | linux-3.10-86c824b9434e764d01489688e4e38aee43b93fcf.tar.gz linux-3.10-86c824b9434e764d01489688e4e38aee43b93fcf.tar.bz2 linux-3.10-86c824b9434e764d01489688e4e38aee43b93fcf.zip |
bio: add documentation to bio_alloc()
Explain that with __GFP_WAIT set it will not fail, and that the caller
must never allocate more than 1 bio at the time.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'fs/bio.c')
-rw-r--r-- | fs/bio.c | 18 |
1 files changed, 18 insertions, 0 deletions
@@ -348,6 +348,24 @@ err: return NULL; } +/** + * bio_alloc - allocate a bio for I/O + * @gfp_mask: the GFP_ mask given to the slab allocator + * @nr_iovecs: number of iovecs to pre-allocate + * + * Description: + * bio_alloc will allocate a bio and associated bio_vec array that can hold + * at least @nr_iovecs entries. Allocations will be done from the + * fs_bio_set. Also see @bio_alloc_bioset. + * + * If %__GFP_WAIT is set, then bio_alloc will always be able to allocate + * a bio. This is due to the mempool guarantees. To make this work, callers + * must never allocate more than 1 bio at the time from this pool. Callers + * that need to allocate more than 1 bio must always submit the previously + * allocate bio for IO before attempting to allocate a new one. Failure to + * do so can cause livelocks under memory pressure. + * + **/ struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs) { struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set); |