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block: loop: mark bvec as ITER_BVEC_FLAG_NO_REF

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loop is one block device, for any bio submitted to this device,
the upper layer does guarantee that pages added to loop's bio won't
go away when the bio is in-flight.

So mark loop's bvec as ITER_BVEC_FLAG_NO_REF then get_page/put_page
can be saved for serving loop's IO.

Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2019-03-28 11:05:31 +08:00 committed by Jens Axboe
parent f6970f83ef
commit 81ba6abd2b
1 changed files with 12 additions and 4 deletions
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16
drivers/block/loop.c
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@ -264,12 +264,20 @@ lo_do_transfer(struct loop_device *lo, int cmd,
return ret;
}
static inline void loop_iov_iter_bvec(struct iov_iter *i,
unsigned int direction, const struct bio_vec *bvec,
unsigned long nr_segs, size_t count)
{
iov_iter_bvec(i, direction, bvec, nr_segs, count);
i->type |= ITER_BVEC_FLAG_NO_REF;
}
static int lo_write_bvec(struct file *file, struct bio_vec *bvec, loff_t *ppos)
{
struct iov_iter i;
ssize_t bw;
iov_iter_bvec(&i, WRITE, bvec, 1, bvec->bv_len);
loop_iov_iter_bvec(&i, WRITE, bvec, 1, bvec->bv_len);
file_start_write(file);
bw = vfs_iter_write(file, &i, ppos, 0);
@ -347,7 +355,7 @@ static int lo_read_simple(struct loop_device *lo, struct request *rq,
ssize_t len;
rq_for_each_segment(bvec, rq, iter) {
iov_iter_bvec(&i, READ, &bvec, 1, bvec.bv_len);
loop_iov_iter_bvec(&i, READ, &bvec, 1, bvec.bv_len);
len = vfs_iter_read(lo->lo_backing_file, &i, &pos, 0);
if (len < 0)
return len;
@ -388,7 +396,7 @@ static int lo_read_transfer(struct loop_device *lo, struct request *rq,
b.bv_offset = 0;
b.bv_len = bvec.bv_len;
iov_iter_bvec(&i, READ, &b, 1, b.bv_len);
loop_iov_iter_bvec(&i, READ, &b, 1, b.bv_len);
len = vfs_iter_read(lo->lo_backing_file, &i, &pos, 0);
if (len < 0) {
ret = len;
@ -555,7 +563,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
}
atomic_set(&cmd->ref, 2);
iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
loop_iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
iter.iov_offset = offset;
cmd->iocb.ki_pos = pos;