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For extent maps, if they are not compressed extents and are adjacent by logical addresses and file offsets, they can be merged into one larger extent map. Such merged extent map will have the higher generation of all the original ones. But this brings a problem for autodefrag, as it relies on accurate extent_map::generation to determine if one extent should be defragged. For merged extent maps, their higher generation can mark some older extents to be defragged while the original extent map doesn't meet the minimal generation threshold. Thus this will cause extra IO. So solve the problem, here we introduce a new flag, EXTENT_FLAG_MERGED, to indicate if the extent map is merged from one or more ems. And for autodefrag, if we find a merged extent map, and its generation meets the generation requirement, we just don't use this one, and go back to defrag_get_extent() to read extent maps from subvolume trees. This could cause more read IO, but should result less defrag data write, so in the long run it should be a win for autodefrag. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
108 lines
2.9 KiB
C
108 lines
2.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef BTRFS_EXTENT_MAP_H
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#define BTRFS_EXTENT_MAP_H
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#include <linux/rbtree.h>
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#include <linux/refcount.h>
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#define EXTENT_MAP_LAST_BYTE ((u64)-4)
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#define EXTENT_MAP_HOLE ((u64)-3)
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#define EXTENT_MAP_INLINE ((u64)-2)
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/* used only during fiemap calls */
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#define EXTENT_MAP_DELALLOC ((u64)-1)
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/* bits for the extent_map::flags field */
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enum {
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/* this entry not yet on disk, don't free it */
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EXTENT_FLAG_PINNED,
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EXTENT_FLAG_COMPRESSED,
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/* pre-allocated extent */
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EXTENT_FLAG_PREALLOC,
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/* Logging this extent */
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EXTENT_FLAG_LOGGING,
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/* Filling in a preallocated extent */
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EXTENT_FLAG_FILLING,
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/* filesystem extent mapping type */
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EXTENT_FLAG_FS_MAPPING,
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/* This em is merged from two or more physically adjacent ems */
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EXTENT_FLAG_MERGED,
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};
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struct extent_map {
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struct rb_node rb_node;
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/* all of these are in bytes */
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u64 start;
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u64 len;
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u64 mod_start;
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u64 mod_len;
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u64 orig_start;
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u64 orig_block_len;
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u64 ram_bytes;
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u64 block_start;
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u64 block_len;
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/*
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* Generation of the extent map, for merged em it's the highest
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* generation of all merged ems.
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* For non-merged extents, it's from btrfs_file_extent_item::generation.
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*/
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u64 generation;
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unsigned long flags;
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/* Used for chunk mappings, flag EXTENT_FLAG_FS_MAPPING must be set */
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struct map_lookup *map_lookup;
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refcount_t refs;
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unsigned int compress_type;
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struct list_head list;
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};
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struct extent_map_tree {
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struct rb_root_cached map;
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struct list_head modified_extents;
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rwlock_t lock;
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};
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static inline int extent_map_in_tree(const struct extent_map *em)
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{
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return !RB_EMPTY_NODE(&em->rb_node);
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}
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static inline u64 extent_map_end(struct extent_map *em)
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{
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if (em->start + em->len < em->start)
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return (u64)-1;
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return em->start + em->len;
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}
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static inline u64 extent_map_block_end(struct extent_map *em)
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{
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if (em->block_start + em->block_len < em->block_start)
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return (u64)-1;
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return em->block_start + em->block_len;
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}
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void extent_map_tree_init(struct extent_map_tree *tree);
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struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
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u64 start, u64 len);
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int add_extent_mapping(struct extent_map_tree *tree,
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struct extent_map *em, int modified);
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void remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em);
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void replace_extent_mapping(struct extent_map_tree *tree,
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struct extent_map *cur,
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struct extent_map *new,
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int modified);
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struct extent_map *alloc_extent_map(void);
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void free_extent_map(struct extent_map *em);
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int __init extent_map_init(void);
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void __cold extent_map_exit(void);
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int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, u64 gen);
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void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em);
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struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
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u64 start, u64 len);
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int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
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struct extent_map_tree *em_tree,
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struct extent_map **em_in, u64 start, u64 len);
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#endif
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