btrfs: document existence of extent_io ops callbacks
Some of the callbacks defined in btree_extent_io_ops and
btrfs_extent_io_ops do always exist so we don't need to check the
existence before each call. This patch just reorders the definition and
documents which are mandatory/optional.
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 67d663a..60d4f1b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4653,9 +4653,12 @@ static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info)
}
static const struct extent_io_ops btree_extent_io_ops = {
- .readpage_end_io_hook = btree_readpage_end_io_hook,
- .readpage_io_failed_hook = btree_io_failed_hook,
+ /* mandatory callbacks */
.submit_bio_hook = btree_submit_bio_hook,
+ .readpage_end_io_hook = btree_readpage_end_io_hook,
/* note we're sharing with inode.c for the merge bio hook */
.merge_bio_hook = btrfs_merge_bio_hook,
+
+ /* optional callbacks */
+ .readpage_io_failed_hook = btree_io_failed_hook,
};
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 78bb4d7..1f8478d 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -92,18 +92,27 @@ typedef int (extent_submit_bio_hook_t)(struct inode *inode, struct bio *bio,
int mirror_num, unsigned long bio_flags,
u64 bio_offset);
struct extent_io_ops {
- int (*fill_delalloc)(struct inode *inode, struct page *locked_page,
- u64 start, u64 end, int *page_started,
- unsigned long *nr_written);
- int (*writepage_start_hook)(struct page *page, u64 start, u64 end);
+ /*
+ * The following callbacks must be allways defined, the function
+ * pointer will be called unconditionally.
+ */
extent_submit_bio_hook_t *submit_bio_hook;
- int (*merge_bio_hook)(struct page *page, unsigned long offset,
- size_t size, struct bio *bio,
- unsigned long bio_flags);
- int (*readpage_io_failed_hook)(struct page *page, int failed_mirror);
int (*readpage_end_io_hook)(struct btrfs_io_bio *io_bio, u64 phy_offset,
struct page *page, u64 start, u64 end,
int mirror);
+ int (*merge_bio_hook)(struct page *page, unsigned long offset,
+ size_t size, struct bio *bio,
+ unsigned long bio_flags);
+
+ /*
+ * Optional hooks, called if the pointer is not NULL
+ */
+ int (*fill_delalloc)(struct inode *inode, struct page *locked_page,
+ u64 start, u64 end, int *page_started,
+ unsigned long *nr_written);
+ int (*readpage_io_failed_hook)(struct page *page, int failed_mirror);
+
+ int (*writepage_start_hook)(struct page *page, u64 start, u64 end);
void (*writepage_end_io_hook)(struct page *page, u64 start, u64 end,
struct extent_state *state, int uptodate);
void (*set_bit_hook)(struct inode *inode, struct extent_state *state,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b904c74..3b327c8 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -10547,10 +10547,13 @@ static const struct file_operations btrfs_dir_file_operations = {
};
static const struct extent_io_ops btrfs_extent_io_ops = {
- .fill_delalloc = run_delalloc_range,
+ /* mandatory callbacks */
.submit_bio_hook = btrfs_submit_bio_hook,
- .merge_bio_hook = btrfs_merge_bio_hook,
.readpage_end_io_hook = btrfs_readpage_end_io_hook,
+ .merge_bio_hook = btrfs_merge_bio_hook,
+
+ /* optional callbacks */
+ .fill_delalloc = run_delalloc_range,
.writepage_end_io_hook = btrfs_writepage_end_io_hook,
.writepage_start_hook = btrfs_writepage_start_hook,
.set_bit_hook = btrfs_set_bit_hook,