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-rw-r--r--block/bio.c43
1 files changed, 24 insertions, 19 deletions
diff --git a/block/bio.c b/block/bio.c
index 71a78d9fb8b7..b64cedc7f87c 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -849,20 +849,14 @@ static int __bio_iov_bvec_add_pages(struct bio *bio, struct iov_iter *iter)
size = bio_add_page(bio, bv->bv_page, len,
bv->bv_offset + iter->iov_offset);
if (size == len) {
- struct page *page;
- int i;
+ if (!bio_flagged(bio, BIO_NO_PAGE_REF)) {
+ struct page *page;
+ int i;
+
+ mp_bvec_for_each_page(page, bv, i)
+ get_page(page);
+ }
- /*
- * For the normal O_DIRECT case, we could skip grabbing this
- * reference and then not have to put them again when IO
- * completes. But this breaks some in-kernel users, like
- * splicing to/from a loop device, where we release the pipe
- * pages unconditionally. If we can fix that case, we can
- * get rid of the get here and the need to call
- * bio_release_pages() at IO completion time.
- */
- mp_bvec_for_each_page(page, bv, i)
- get_page(page);
iov_iter_advance(iter, size);
return 0;
}
@@ -925,10 +919,12 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
* This takes either an iterator pointing to user memory, or one pointing to
* kernel pages (BVEC iterator). If we're adding user pages, we pin them and
* map them into the kernel. On IO completion, the caller should put those
- * pages. For now, when adding kernel pages, we still grab a reference to the
- * page. This isn't strictly needed for the common case, but some call paths
- * end up releasing pages from eg a pipe and we can't easily control these.
- * See comment in __bio_iov_bvec_add_pages().
+ * pages. If we're adding kernel pages, and the caller told us it's safe to
+ * do so, we just have to add the pages to the bio directly. We don't grab an
+ * extra reference to those pages (the user should already have that), and we
+ * don't put the page on IO completion. The caller needs to check if the bio is
+ * flagged BIO_NO_PAGE_REF on IO completion. If it isn't, then pages should be
+ * released.
*
* The function tries, but does not guarantee, to pin as many pages as
* fit into the bio, or are requested in *iter, whatever is smaller. If
@@ -940,6 +936,13 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
const bool is_bvec = iov_iter_is_bvec(iter);
unsigned short orig_vcnt = bio->bi_vcnt;
+ /*
+ * If this is a BVEC iter, then the pages are kernel pages. Don't
+ * release them on IO completion, if the caller asked us to.
+ */
+ if (is_bvec && iov_iter_bvec_no_ref(iter))
+ bio_set_flag(bio, BIO_NO_PAGE_REF);
+
do {
int ret;
@@ -1696,7 +1699,8 @@ static void bio_dirty_fn(struct work_struct *work)
next = bio->bi_private;
bio_set_pages_dirty(bio);
- bio_release_pages(bio);
+ if (!bio_flagged(bio, BIO_NO_PAGE_REF))
+ bio_release_pages(bio);
bio_put(bio);
}
}
@@ -1713,7 +1717,8 @@ void bio_check_pages_dirty(struct bio *bio)
goto defer;
}
- bio_release_pages(bio);
+ if (!bio_flagged(bio, BIO_NO_PAGE_REF))
+ bio_release_pages(bio);
bio_put(bio);
return;
defer: