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>
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@@ -21,6 +21,16 @@
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#include "ref-cache.h"
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#include "transaction.h"
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/*
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* leaf refs are used to cache the information about which extents
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* a given leaf has references on. This allows us to process that leaf
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* in btrfs_drop_snapshot without needing to read it back from disk.
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*/
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/*
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* kmalloc a leaf reference struct and update the counters for the
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* total ref cache size
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*/
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struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
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int nr_extents)
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{
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@@ -40,6 +50,10 @@ struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
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return ref;
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}
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/*
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* free a leaf reference struct and update the counters for the
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* total ref cache size
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*/
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void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
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{
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if (!ref)
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@@ -135,6 +149,10 @@ int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
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return 0;
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}
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/*
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* find the leaf ref for a given extent. This returns the ref struct with
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* a usage reference incremented
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*/
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struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
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u64 bytenr)
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{
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@@ -160,6 +178,10 @@ again:
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return NULL;
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}
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/*
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* add a fully filled in leaf ref struct
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* remove all the refs older than a given root generation
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*/
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int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
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int shared)
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{
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@@ -184,6 +206,10 @@ int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
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return ret;
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}
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/*
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* remove a single leaf ref from the tree. This drops the ref held by the tree
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* only
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*/
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int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
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{
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struct btrfs_leaf_ref_tree *tree;
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