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loop: add helper lo_rw_aio_prep()

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Add helper lo_rw_aio_prep() to separate the preparation phase(setting up bio
vectors and initializing the iocb structure) from the actual I/O execution
in the loop block driver.

Prepare for using NOWAIT to improve loop performance.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei
2025-10-15 19:07:27 +08:00
committed by Jens Axboe
parent c3e6c11147
commit fd858d1ca9
1 changed files with 40 additions and 23 deletions
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63
drivers/block/loop.c
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@@ -350,21 +350,15 @@ static inline unsigned lo_cmd_nr_bvec(struct loop_cmd *cmd)
return nr_bvec;
}
static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
loff_t pos, int rw)
static int lo_rw_aio_prep(struct loop_device *lo, struct loop_cmd *cmd,
unsigned nr_bvec, loff_t pos)
{
struct iov_iter iter;
struct req_iterator rq_iter;
struct bio_vec *bvec;
struct request *rq = blk_mq_rq_from_pdu(cmd);
struct bio *bio = rq->bio;
struct file *file = lo->lo_backing_file;
struct bio_vec tmp;
unsigned int offset;
int nr_bvec = lo_cmd_nr_bvec(cmd);
int ret;
if (rq->bio != rq->biotail) {
struct req_iterator rq_iter;
struct bio_vec *bvec;
struct bio_vec tmp;
bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
GFP_NOIO);
@@ -382,8 +376,42 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
*bvec = tmp;
bvec++;
}
bvec = cmd->bvec;
} else {
cmd->bvec = NULL;
}
cmd->iocb.ki_pos = pos;
cmd->iocb.ki_filp = lo->lo_backing_file;
cmd->iocb.ki_ioprio = req_get_ioprio(rq);
if (cmd->use_aio) {
cmd->iocb.ki_complete = lo_rw_aio_complete;
cmd->iocb.ki_flags = IOCB_DIRECT;
} else {
cmd->iocb.ki_complete = NULL;
cmd->iocb.ki_flags = 0;
}
return 0;
}
static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
loff_t pos, int rw)
{
struct iov_iter iter;
struct bio_vec *bvec;
struct request *rq = blk_mq_rq_from_pdu(cmd);
struct bio *bio = rq->bio;
struct file *file = lo->lo_backing_file;
unsigned int offset;
int nr_bvec = lo_cmd_nr_bvec(cmd);
int ret;
ret = lo_rw_aio_prep(lo, cmd, nr_bvec, pos);
if (unlikely(ret))
return ret;
if (cmd->bvec) {
offset = 0;
bvec = cmd->bvec;
} else {
/*
* Same here, this bio may be started from the middle of the
@@ -398,17 +426,6 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
iter.iov_offset = offset;
cmd->iocb.ki_pos = pos;
cmd->iocb.ki_filp = file;
cmd->iocb.ki_ioprio = req_get_ioprio(rq);
if (cmd->use_aio) {
cmd->iocb.ki_complete = lo_rw_aio_complete;
cmd->iocb.ki_flags = IOCB_DIRECT;
} else {
cmd->iocb.ki_complete = NULL;
cmd->iocb.ki_flags = 0;
}
if (rw == ITER_SOURCE) {
kiocb_start_write(&cmd->iocb);
ret = file->f_op->write_iter(&cmd->iocb, &iter);