block: never take page references for ITER_BVEC

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.

Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 6 insertions, 37 deletions

diff --git a/block/bio.c b/block/bio.c
index 1cbf2a7c245e..5733b9426231 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.
  *