btrfs: introduce submit_compressed_bio() for compression

The new helper, submit_compressed_bio(), will aggregate the following
work:

- Increase compressed_bio::pending_bios
- Remap the endio function
- Map and submit the bio

This slightly reorders calls to btrfs_csum_one_bio or
btrfs_lookup_bio_sums but but none of them does anything regarding IO
submission so this is effectively no change. We mainly care about order
of

- atomic_inc
- btrfs_bio_wq_end_io
- btrfs_map_bio

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index dabb3a88f2e5b130f91293ed2e662c3eab1b6e9a..60b4da6ce93fb2fb42470e97fbe2df0ee96c436f 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -419,6 +419,21 @@ out:
        bio_put(bio);
 }
 
+static blk_status_t submit_compressed_bio(struct btrfs_fs_info *fs_info,
+                                         struct compressed_bio *cb,
+                                         struct bio *bio, int mirror_num)
+{
+       blk_status_t ret;
+
+       ASSERT(bio->bi_iter.bi_size);
+       atomic_inc(&cb->pending_bios);
+       ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
+       if (ret)
+               return ret;
+       ret = btrfs_map_bio(fs_info, bio, mirror_num);
+       return ret;
+}
+
 /*
  * worker function to build and submit bios for previously compressed pages.
  * The corresponding pages in the inode should be marked for writeback
@@ -514,19 +529,13 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 
                page->mapping = NULL;
                if (submit || len < PAGE_SIZE) {
-                       atomic_inc(&cb->pending_bios);
-                       ret = btrfs_bio_wq_end_io(fs_info, bio,
-                                                 BTRFS_WQ_ENDIO_DATA);
-                       if (ret)
-                               goto finish_cb;
-
                        if (!skip_sum) {
                                ret = btrfs_csum_one_bio(inode, bio, start, 1);
                                if (ret)
                                        goto finish_cb;
                        }
 
-                       ret = btrfs_map_bio(fs_info, bio, 0);
+                       ret = submit_compressed_bio(fs_info, cb, bio, 0);
                        if (ret)
                                goto finish_cb;
 
@@ -553,18 +562,13 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
                cond_resched();
        }
 
-       atomic_inc(&cb->pending_bios);
-       ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
-       if (ret)
-               goto last_bio;
-
        if (!skip_sum) {
                ret = btrfs_csum_one_bio(inode, bio, start, 1);
                if (ret)
                        goto last_bio;
        }
 
-       ret = btrfs_map_bio(fs_info, bio, 0);
+       ret = submit_compressed_bio(fs_info, cb, bio, 0);
        if (ret)
                goto last_bio;
 
@@ -868,12 +872,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
                if (submit || bio_add_page(comp_bio, page, pg_len, 0) < pg_len) {
                        unsigned int nr_sectors;
 
-                       atomic_inc(&cb->pending_bios);
-                       ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
-                                                 BTRFS_WQ_ENDIO_DATA);
-                       if (ret)
-                               goto finish_cb;
-
                        ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
                        if (ret)
                                goto finish_cb;
@@ -882,7 +880,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
                                                  fs_info->sectorsize);
                        sums += fs_info->csum_size * nr_sectors;
 
-                       ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
+                       ret = submit_compressed_bio(fs_info, cb, comp_bio, mirror_num);
                        if (ret)
                                goto finish_cb;
 
@@ -897,16 +895,11 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
                cur_disk_byte += pg_len;
        }
 
-       atomic_inc(&cb->pending_bios);
-       ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
-       if (ret)
-               goto last_bio;
-
        ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
        if (ret)
                goto last_bio;
 
-       ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
+       ret = submit_compressed_bio(fs_info, cb, comp_bio, mirror_num);
        if (ret)
                goto last_bio;