Commit 4088a47e authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

btrfs: add manual PSI accounting for compressed reads 



btrfs compressed reads try to always read the entire compressed chunk,
even if only a subset is requested.  Currently this is covered by the
magic PSI accounting underneath submit_bio, but that is about to go
away. Instead add manual psi_memstall_{enter,leave} annotations.

Note that for readahead this really should be using readahead_expand,
but the additionals reads are also done for plain ->read_folio where
readahead_expand can't work, so this overall logic is left as-is for
now.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarDavid Sterba <dsterba@suse.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220915094200.139713-4-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 527eb453

fs/btrfs/compression.c

+12 −2
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/string.h>

#include <linux/backing-dev.h>

#include <linux/writeback.h>

#include <linux/psi.h>

#include <linux/slab.h>

#include <linux/sched/mm.h>

#include <linux/log2.h>
@@ -519,7 +520,8 @@ static u64 bio_end_offset(struct bio *bio) 
 */

static noinline int add_ra_bio_pages(struct inode *inode,

				     u64 compressed_end,

				     struct compressed_bio *cb)

				     struct compressed_bio *cb,

				     unsigned long *pflags)

{

	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

	unsigned long end_index;
@@ -588,6 +590,9 @@ static noinline int add_ra_bio_pages(struct inode *inode, 
			continue;

		}



		if (PageWorkingset(page))

			psi_memstall_enter(pflags);



		ret = set_page_extent_mapped(page);

		if (ret < 0) {

			unlock_page(page);
@@ -674,6 +679,8 @@ void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, 
	u64 em_len;

	u64 em_start;

	struct extent_map *em;

	/* Initialize to 1 to make skip psi_memstall_leave unless needed */

	unsigned long pflags = 1;

	blk_status_t ret;

	int ret2;

	int i;
@@ -729,7 +736,7 @@ void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, 
		goto fail;

	}



	add_ra_bio_pages(inode, em_start + em_len, cb);

	add_ra_bio_pages(inode, em_start + em_len, cb, &pflags);



	/* include any pages we added in add_ra-bio_pages */

	cb->len = bio->bi_iter.bi_size;
@@ -810,6 +817,9 @@ void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, 
		}

	}



	if (!pflags)

		psi_memstall_leave(&pflags);



	if (refcount_dec_and_test(&cb->pending_ios))

		finish_compressed_bio_read(cb);

	return;