[PATCH v2 2/6] btrfs: add READAHEAD extent buffer flag

[Arne Jansen]

Add a READAHEAD extent buffer flag.
Add a function to trigger a read with this flag set.

Changes v2:
 - use extent buffer flags instead of extent state flags

Signed-off-by: Arne Jansen <sensi...@gmx.net>
---
 fs/btrfs/disk-io.c   |   32 ++++++++++++++++++++++++++++++++
 fs/btrfs/disk-io.h   |    2 ++
 fs/btrfs/extent_io.h |    1 +
 3 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 0339cc0..0195172 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -945,6 +945,38 @@ int readahead_tree_block(struct btrfs_root *root, u64 
bytenr, u32 blocksize,
        return ret;
 }
 
+int reada_tree_block_flagged(struct btrfs_root *root, u64 bytenr, u32 
blocksize,
+                        int mirror_num, struct extent_buffer **eb)
+{
+       struct extent_buffer *buf = NULL;
+       struct inode *btree_inode = root->fs_info->btree_inode;
+       struct extent_io_tree *io_tree = &BTRFS_I(btree_inode)->io_tree;
+       int ret;
+
+       buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
+       if (!buf)
+               return 0;
+
+       set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags);
+
+       ret = read_extent_buffer_pages(io_tree, buf, 0, 0, 1, btree_get_extent,
+                                mirror_num);
+       if (ret) {
+               free_extent_buffer(buf);
+               return ret;
+       }
+
+       if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) {
+               *eb = buf;
+               return -EIO;
+       } else if (extent_buffer_uptodate(io_tree, buf, NULL)) {
+               *eb = buf;
+       } else {
+               free_extent_buffer(buf);
+       }
+       return 0;
+}
+
 struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root,
                                            u64 bytenr, u32 blocksize)
 {
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index a0b610a..fb35c4e 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -40,6 +40,8 @@ struct extent_buffer *read_tree_block(struct btrfs_root 
*root, u64 bytenr,
                                      u32 blocksize, u64 parent_transid);
 int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,
                         u64 parent_transid);
+int reada_tree_block_flagged(struct btrfs_root *root, u64 bytenr, u32 
blocksize,
+                        int mirror_num, struct extent_buffer **eb);
 struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
                                                   u64 bytenr, u32 blocksize);
 int clean_tree_block(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 118c30b..e0a09e8 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -32,6 +32,7 @@
 #define EXTENT_BUFFER_BLOCKING 1
 #define EXTENT_BUFFER_DIRTY 2
 #define EXTENT_BUFFER_CORRUPT 3
+#define EXTENT_BUFFER_READAHEAD 4      /* this got triggered by readahead */
 
 /* these are flags for extent_clear_unlock_delalloc */
 #define EXTENT_CLEAR_UNLOCK_PAGE 0x1
-- 
1.7.3.4

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