Btrfs: add and improve comments
This improves the comments at the top of many functions. It didn't
dive into the guts of functions because I was trying to
avoid merging problems with the new allocator and back reference work.
extent-tree.c and volumes.c were both skipped, and there is definitely
more work todo in cleaning and commenting the code.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 0577fda..0b2e623 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -25,27 +25,58 @@
/* in memory btrfs inode */
struct btrfs_inode {
+ /* which subvolume this inode belongs to */
struct btrfs_root *root;
+
+ /* the block group preferred for allocations. This pointer is buggy
+ * and needs to be replaced with a bytenr instead
+ */
struct btrfs_block_group_cache *block_group;
+
+ /* key used to find this inode on disk. This is used by the code
+ * to read in roots of subvolumes
+ */
struct btrfs_key location;
+
+ /* the extent_tree has caches of all the extent mappings to disk */
struct extent_map_tree extent_tree;
+
+ /* the io_tree does range state (DIRTY, LOCKED etc) */
struct extent_io_tree io_tree;
+
+ /* special utility tree used to record which mirrors have already been
+ * tried when checksums fail for a given block
+ */
struct extent_io_tree io_failure_tree;
+
+ /* held while inserting checksums to avoid races */
struct mutex csum_mutex;
+
+ /* held while inesrting or deleting extents from files */
struct mutex extent_mutex;
+
+ /* held while logging the inode in tree-log.c */
struct mutex log_mutex;
- struct inode vfs_inode;
+
+ /* used to order data wrt metadata */
struct btrfs_ordered_inode_tree ordered_tree;
+ /* standard acl pointers */
struct posix_acl *i_acl;
struct posix_acl *i_default_acl;
/* for keeping track of orphaned inodes */
struct list_head i_orphan;
+ /* list of all the delalloc inodes in the FS. There are times we need
+ * to write all the delalloc pages to disk, and this list is used
+ * to walk them all.
+ */
struct list_head delalloc_inodes;
- /* full 64 bit generation number */
+ /* full 64 bit generation number, struct vfs_inode doesn't have a big
+ * enough field for this.
+ */
u64 generation;
/*
@@ -57,10 +88,25 @@
*/
u64 logged_trans;
- /* trans that last made a change that should be fully fsync'd */
+ /*
+ * trans that last made a change that should be fully fsync'd. This
+ * gets reset to zero each time the inode is logged
+ */
u64 log_dirty_trans;
+
+ /* total number of bytes pending delalloc, used by stat to calc the
+ * real block usage of the file
+ */
u64 delalloc_bytes;
+
+ /*
+ * the size of the file stored in the metadata on disk. data=ordered
+ * means the in-memory i_size might be larger than the size on disk
+ * because not all the blocks are written yet.
+ */
u64 disk_i_size;
+
+ /* flags field from the on disk inode */
u32 flags;
/*
@@ -68,6 +114,8 @@
* number for new files that are created
*/
u64 index_cnt;
+
+ struct inode vfs_inode;
};
static inline struct btrfs_inode *BTRFS_I(struct inode *inode)