[PATCH 9/9] block: never take page references for ITER_BVEC

Christoph Hellwig
2019-06-26T13:49:52Z

If we pass pages through an iov_iter we always already have a reference
in the caller. Thus remove the ITER_BVEC_FLAG_NO_REF and don't take
reference to pages by default for bvec backed iov_iters.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
---
block/bio.c | 14 +-------------
drivers/block/loop.c | 16 ++++------------
fs/io_uring.c | 3 ---
include/linux/uio.h | 10 +---------
4 files changed, 6 insertions(+), 37 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index a96d33d2de44..3c9225caff8d 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -836,15 +836,6 @@ int bio_add_page(struct bio *bio, struct page *page,
}
EXPORT_SYMBOL(bio_add_page);

-static void bio_get_pages(struct bio *bio)
-{
- struct bvec_iter_all iter_all;
- struct bio_vec *bvec;
-
- bio_for_each_segment_all(bvec, bio, iter_all)
- get_page(bvec->bv_page);
-}
-
void bio_release_pages(struct bio *bio, bool mark_dirty)
{
struct bvec_iter_all iter_all;
@@ -960,11 +951,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
ret = __bio_iov_iter_get_pages(bio, iter);
} while (!ret && iov_iter_count(iter) && !bio_full(bio));

- if (iov_iter_bvec_no_ref(iter))
+ if (is_bvec)
bio_set_flag(bio, BIO_NO_PAGE_REF);
- else if (is_bvec)
- bio_get_pages(bio);
-
return bio->bi_vcnt ? 0 : ret;
}

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f11b7dc16e9d..44c9985f352a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -264,20 +264,12 @@ 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;

- loop_iov_iter_bvec(&i, WRITE, bvec, 1, bvec->bv_len);
+ iov_iter_bvec(&i, WRITE, bvec, 1, bvec->bv_len);

file_start_write(file);
bw = vfs_iter_write(file, &i, ppos, 0);
@@ -355,7 +347,7 @@ static int lo_read_simple(struct loop_device *lo, struct request *rq,
ssize_t len;

rq_for_each_segment(bvec, rq, iter) {
- loop_iov_iter_bvec(&i, READ, &bvec, 1, bvec.bv_len);
+ 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;
@@ -396,7 +388,7 @@ static int lo_read_transfer(struct loop_device *lo, struct request *rq,
b.bv_offset = 0;
b.bv_len = bvec.bv_len;

- loop_iov_iter_bvec(&i, READ, &b, 1, b.bv_len);
+ 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;
@@ -563,7 +555,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
}
atomic_set(&cmd->ref, 2);

- loop_iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
+ iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
iter.iov_offset = offset;

cmd->iocb.ki_pos = pos;
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 86a2bd721900..eb6ab1507913 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -997,9 +997,6 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len);
if (offset)
iov_iter_advance(iter, offset);
-
- /* don't drop a reference to these pages */
- iter->type |= ITER_BVEC_FLAG_NO_REF;
return 0;
}

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 2c90a0842ee8..cea1761c5672 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -19,9 +19,6 @@ struct kvec {
};

enum iter_type {
- /* set if ITER_BVEC doesn't hold a bv_page ref */
- ITER_BVEC_FLAG_NO_REF = 2,
-
/* iter types */
ITER_IOVEC = 4,
ITER_KVEC = 8,
@@ -56,7 +53,7 @@ struct iov_iter {

static inline enum iter_type iov_iter_type(const struct iov_iter *i)
{
- return i->type & ~(READ | WRITE | ITER_BVEC_FLAG_NO_REF);
+ return i->type & ~(READ | WRITE);
}

static inline bool iter_is_iovec(const struct iov_iter *i)
@@ -89,11 +86,6 @@ static inline unsigned char iov_iter_rw(const struct iov_iter *i)
return i->type & (READ | WRITE);
}

-static inline bool iov_iter_bvec_no_ref(const struct iov_iter *i)
-{
- return (i->type & ITER_BVEC_FLAG_NO_REF) != 0;
-}
-
/*
* Total number of bytes covered by an iovec.
*
--
2.20.1