[rh7,29/30] fs: direct-io: don't dirtying pages for ITER_BVEC/ITER_KVEC direct read

Submitted by Kirill Tkhai on May 20, 2020, 4:06 p.m.

Details

Message ID 158999078021.2234365.574750858418617812.stgit@localhost.localdomain
State New
Series "fs, direct_IO: Switch to iov_iter and allow bio_vec for ext4"
Headers show

Commit Message

Kirill Tkhai May 20, 2020, 4:06 p.m.
From: Ming Lei <ming.lei@canonical.com>

ms commit 53cbf3b157a0

When direct read IO is submitted from kernel, it is often
unnecessary to dirty pages, for example of loop, dirtying pages
have been considered in the upper filesystem(over loop) side
already, and they don't need to be dirtied again.

So this patch doesn't dirtying pages for ITER_BVEC/ITER_KVEC
direct read, and loop should be the 1st case to use ITER_BVEC/ITER_KVEC
for direct read I/O.

The patch is based on previous Dave's patch.

Reviewed-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

Otherwise bio_set_pages_dirty() results in deadlock for bvec pages.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 fs/direct-io.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Patch hide | download patch | download mbox

diff --git a/fs/direct-io.c b/fs/direct-io.c
index f7e464d8bcdb..1c3a4851e5cf 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -129,6 +129,7 @@  struct dio {
 	int page_errors;		/* errno from get_user_pages() */
 	int is_async;			/* is IO async ? */
 	bool defer_completion;		/* defer AIO completion to workqueue? */
+	bool should_dirty;		/* if pages should be dirtied */
 	int io_error;			/* IO error in completion path */
 	unsigned long refcount;		/* direct_io_worker() and bios */
 	struct bio *bio_list;		/* singly linked via bi_private */
@@ -471,7 +472,7 @@  static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
 	dio->refcount++;
 	spin_unlock_irqrestore(&dio->bio_lock, flags);
 
-	if (dio->is_async && dio->rw == READ)
+	if (dio->is_async && dio->rw == READ && dio->should_dirty)
 		bio_set_pages_dirty(bio);
 
 	if (sdio->submit_io)
@@ -542,13 +543,14 @@  static int dio_bio_complete(struct dio *dio, struct bio *bio)
 	if (!uptodate)
 		dio->io_error = -EIO;
 
-	if (dio->is_async && dio->rw == READ) {
+	if (dio->is_async && dio->rw == READ && dio->should_dirty) {
 		bio_check_pages_dirty(bio);	/* transfers ownership */
 	} else {
 		bio_for_each_segment_all(bvec, bio, i) {
 			struct page *page = bvec->bv_page;
 
-			if (dio->rw == READ && !PageCompound(page))
+			if (dio->rw == READ && !PageCompound(page) &&
+					dio->should_dirty)
 				set_page_dirty_lock(page);
 			page_cache_release(page);
 		}
@@ -1324,6 +1326,7 @@  do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	spin_lock_init(&dio->bio_lock);
 	dio->refcount = 1;
 
+	dio->should_dirty = iov_iter_has_iovec(iter);
 	sdio.iter = iter;
 	sdio.final_block_in_request =
 		(offset + iov_iter_count(iter)) >> blkbits;