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: Christoph Hellwig <hch@lst.de>
Acked-by: David Sterba <dsterba@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220915094200.139713-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index e84d22c..370788b 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -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;