Commit 27de0ee3 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Add block plugging to read paths 



This will help with some of the btree_trans srcu lock hold time warnings
that are still turning up; submit_bio() can block for awhile if the
device is sufficiently congested.

It's not a perfect solution since blk_plug bios are submitted when
scheduling; we might want a way to disable the "submit on context
switch" behaviour, or switch to our own plugging in the future.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent be5a7be1

fs/bcachefs/fs-io-buffered.c

+18 −1
Original line number Diff line number Diff line
@@ -248,6 +248,7 @@ void bch2_readahead(struct readahead_control *ractl) 
	struct bch_io_opts opts;

	struct folio *folio;

	struct readpages_iter readpages_iter;

	struct blk_plug plug;



	bch2_inode_opts_get(&opts, c, &inode->ei_inode);
@@ -255,6 +256,16 @@ void bch2_readahead(struct readahead_control *ractl) 
	if (ret)

		return;



	/*

	 * Besides being a general performance optimization, plugging helps with

	 * avoiding btree transaction srcu warnings - submitting a bio can

	 * block, and we don't want todo that with the transaction locked.

	 *

	 * However, plugged bios are submitted when we schedule; we ideally

	 * would have our own scheduler hook to call unlock_long() before

	 * scheduling.

	 */

	blk_start_plug(&plug);

	bch2_pagecache_add_get(inode);



	struct btree_trans *trans = bch2_trans_get(c);
@@ -281,7 +292,7 @@ void bch2_readahead(struct readahead_control *ractl) 
	bch2_trans_put(trans);



	bch2_pagecache_add_put(inode);



	blk_finish_plug(&plug);

	darray_exit(&readpages_iter.folios);

}
@@ -296,9 +307,13 @@ int bch2_read_single_folio(struct folio *folio, struct address_space *mapping) 
	struct bch_fs *c = inode->v.i_sb->s_fs_info;

	struct bch_read_bio *rbio;

	struct bch_io_opts opts;

	struct blk_plug plug;

	int ret;

	DECLARE_COMPLETION_ONSTACK(done);



	BUG_ON(folio_test_uptodate(folio));

	BUG_ON(folio_test_dirty(folio));



	if (!bch2_folio_create(folio, GFP_KERNEL))

		return -ENOMEM;
@@ -313,7 +328,9 @@ int bch2_read_single_folio(struct folio *folio, struct address_space *mapping) 
	rbio->bio.bi_iter.bi_sector = folio_sector(folio);

	BUG_ON(!bio_add_folio(&rbio->bio, folio, folio_size(folio), 0));



	blk_start_plug(&plug);

	bch2_trans_run(c, (bchfs_read(trans, rbio, inode_inum(inode), NULL), 0));

	blk_finish_plug(&plug);

	wait_for_completion(&done);



	ret = blk_status_to_errno(rbio->bio.bi_status);

fs/bcachefs/fs-io-direct.c

+5 −0
Original line number Diff line number Diff line
@@ -70,6 +70,7 @@ static int bch2_direct_IO_read(struct kiocb *req, struct iov_iter *iter) 
	struct bch_io_opts opts;

	struct dio_read *dio;

	struct bio *bio;

	struct blk_plug plug;

	loff_t offset = req->ki_pos;

	bool sync = is_sync_kiocb(req);

	size_t shorten;
@@ -128,6 +129,8 @@ static int bch2_direct_IO_read(struct kiocb *req, struct iov_iter *iter) 
	 */

	dio->should_dirty = iter_is_iovec(iter);



	blk_start_plug(&plug);



	goto start;

	while (iter->count) {

		bio = bio_alloc_bioset(NULL,
@@ -160,6 +163,8 @@ static int bch2_direct_IO_read(struct kiocb *req, struct iov_iter *iter) 
		bch2_read(c, rbio_init(bio, opts), inode_inum(inode));

	}



	blk_finish_plug(&plug);



	iter->count += shorten;



	if (sync) {