[PATCH V5 11/16] block: ublk_drv: cleanup ublk_copy_user_pages

Ming Lei
2023-03-28T15:14:28Z

Clean up ublk_copy_user_pages() by using iov iter, and code
gets simplified a lot and becomes much more readable than before.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
drivers/block/ublk_drv.c | 112 +++++++++++++++++----------------------
1 file changed, 49 insertions(+), 63 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index fdccbf5fdaa1..cca0e95a89d8 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -419,49 +419,39 @@ static const struct block_device_operations ub_fops = {

#define UBLK_MAX_PIN_PAGES 32

-struct ublk_map_data {
- const struct request *rq;
- unsigned long ubuf;
- unsigned int len;
-};
-
struct ublk_io_iter {
struct page *pages[UBLK_MAX_PIN_PAGES];
- unsigned pg_off; /* offset in the 1st page in pages */
- int nr_pages; /* how many page pointers in pages */
struct bio *bio;
struct bvec_iter iter;
};

-static inline unsigned ublk_copy_io_pages(struct ublk_io_iter *data,
- unsigned max_bytes, bool to_vm)
+/* return how many pages are copied */
+static void ublk_copy_io_pages(struct ublk_io_iter *data,
+ size_t total, size_t pg_off, int dir)
{
- const unsigned total = min_t(unsigned, max_bytes,
- PAGE_SIZE - data->pg_off +
- ((data->nr_pages - 1) << PAGE_SHIFT));
unsigned done = 0;
unsigned pg_idx = 0;

while (done < total) {
struct bio_vec bv = bio_iter_iovec(data->bio, data->iter);
- const unsigned int bytes = min3(bv.bv_len, total - done,
- (unsigned)(PAGE_SIZE - data->pg_off));
+ unsigned int bytes = min3(bv.bv_len, (unsigned)total - done,
+ (unsigned)(PAGE_SIZE - pg_off));
void *bv_buf = bvec_kmap_local(&bv);
void *pg_buf = kmap_local_page(data->pages[pg_idx]);

- if (to_vm)
- memcpy(pg_buf + data->pg_off, bv_buf, bytes);
+ if (dir == ITER_DEST)
+ memcpy(pg_buf + pg_off, bv_buf, bytes);
else
- memcpy(bv_buf, pg_buf + data->pg_off, bytes);
+ memcpy(bv_buf, pg_buf + pg_off, bytes);

kunmap_local(pg_buf);
kunmap_local(bv_buf);

/* advance page array */
- data->pg_off += bytes;
- if (data->pg_off == PAGE_SIZE) {
+ pg_off += bytes;
+ if (pg_off == PAGE_SIZE) {
pg_idx += 1;
- data->pg_off = 0;
+ pg_off = 0;
}

done += bytes;
@@ -475,41 +465,40 @@ static inline unsigned ublk_copy_io_pages(struct ublk_io_iter *data,
data->iter = data->bio->bi_iter;
}
}
-
- return done;
}

-static int ublk_copy_user_pages(struct ublk_map_data *data, bool to_vm)
+/*
+ * Copy data between request pages and io_iter, and 'offset'
+ * is the start point of linear offset of request.
+ */
+static size_t ublk_copy_user_pages(const struct request *req,
+ struct iov_iter *uiter, int dir)
{
- const unsigned int gup_flags = to_vm ? FOLL_WRITE : 0;
- const unsigned long start_vm = data->ubuf;
- unsigned int done = 0;
struct ublk_io_iter iter = {
- .pg_off = start_vm & (PAGE_SIZE - 1),
- .bio = data->rq->bio,
- .iter = data->rq->bio->bi_iter,
+ .bio = req->bio,
+ .iter = req->bio->bi_iter,
};
- const unsigned int nr_pages = round_up(data->len +
- (start_vm & (PAGE_SIZE - 1)), PAGE_SIZE) >> PAGE_SHIFT;
-
- while (done < nr_pages) {
- const unsigned to_pin = min_t(unsigned, UBLK_MAX_PIN_PAGES,
- nr_pages - done);
- unsigned i, len;
-
- iter.nr_pages = get_user_pages_fast(start_vm +
- (done << PAGE_SHIFT), to_pin, gup_flags,
- iter.pages);
- if (iter.nr_pages <= 0)
- return done == 0 ? iter.nr_pages : done;
- len = ublk_copy_io_pages(&iter, data->len, to_vm);
- for (i = 0; i < iter.nr_pages; i++) {
- if (to_vm)
+ size_t done = 0;
+
+ while (iov_iter_count(uiter) && iter.bio) {
+ unsigned nr_pages;
+ size_t len, off;
+ int i;
+
+ len = iov_iter_get_pages2(uiter, iter.pages,
+ iov_iter_count(uiter),
+ UBLK_MAX_PIN_PAGES, &off);
+ if (len <= 0)
+ return done;
+
+ ublk_copy_io_pages(&iter, len, off, dir);
+ nr_pages = DIV_ROUND_UP(len + off, PAGE_SIZE);
+ for (i = 0; i < nr_pages; i++) {
+ if (dir == ITER_DEST)
set_page_dirty(iter.pages[i]);
put_page(iter.pages[i]);
}
- data->len -= len;
- done += iter.nr_pages;
+ done += len;
}

return done;
@@ -536,15 +525,14 @@ static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
* context is pretty fast, see ublk_pin_user_pages
*/
if (ublk_need_map_req(req)) {
- struct ublk_map_data data = {
- .rq = req,
- .ubuf = io->addr,
- .len = rq_bytes,
- };
+ struct iov_iter iter;
+ struct iovec iov;
+ const int dir = ITER_DEST;

- ublk_copy_user_pages(&data, true);
+ import_single_range(dir, u64_to_user_ptr(io->addr), rq_bytes,
+ &iov, &iter);

- return rq_bytes - data.len;
+ return ublk_copy_user_pages(req, &iter, dir);
}
return rq_bytes;
}
@@ -556,17 +544,15 @@ static int ublk_unmap_io(const struct ublk_queue *ubq,
const unsigned int rq_bytes = blk_rq_bytes(req);

if (ublk_need_unmap_req(req)) {
- struct ublk_map_data data = {
- .rq = req,
- .ubuf = io->addr,
- .len = io->res,
- };
+ struct iov_iter iter;
+ struct iovec iov;
+ const int dir = ITER_SOURCE;

WARN_ON_ONCE(io->res > rq_bytes);

- ublk_copy_user_pages(&data, false);
-
- return io->res - data.len;
+ import_single_range(dir, u64_to_user_ptr(io->addr), io->res,
+ &iov, &iter);
+ return ublk_copy_user_pages(req, &iter, dir);
}
return rq_bytes;
}
--
2.39.2