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f86f7a75e2
Currently, in struct extent_map, we use an unsigned int (32 bits) to identify the compression type of an extent and an unsigned long (64 bits on a 64 bits platform, 32 bits otherwise) for flags. We are only using 6 different flags, so an unsigned long is excessive and we can use flags to identify the compression type instead of using a dedicated 32 bits field. We can easily have tens or hundreds of thousands (or more) of extent maps on busy and large filesystems, specially with compression enabled or many or large files with tons of small extents. So it's convenient to have the extent_map structure as small as possible in order to use less memory. So remove the compression type field from struct extent_map, use flags to identify the compression type and shorten the flags field from an unsigned long to a u32. This saves 8 bytes (on 64 bits platforms) and reduces the size of the structure from 136 bytes down to 128 bytes, using now only two cache lines, and increases the number of extent maps we can have per 4K page from 30 to 32. By using a u32 for the flags instead of an unsigned long, we no longer use test_bit(), set_bit() and clear_bit(), but that level of atomicity is not needed as most flags are never cleared once set (before adding an extent map to the tree), and the ones that can be cleared or set after an extent map is added to the tree, are always performed while holding the write lock on the extent map tree, while the reader holds a lock on the tree or tests for a flag that never changes once the extent map is in the tree (such as compression flags). Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
142 lines
3.9 KiB
C
142 lines
3.9 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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#include "compression.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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/* 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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ENUM_BIT(EXTENT_FLAG_PINNED),
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ENUM_BIT(EXTENT_FLAG_COMPRESS_ZLIB),
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ENUM_BIT(EXTENT_FLAG_COMPRESS_LZO),
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ENUM_BIT(EXTENT_FLAG_COMPRESS_ZSTD),
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/* pre-allocated extent */
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ENUM_BIT(EXTENT_FLAG_PREALLOC),
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/* Logging this extent */
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ENUM_BIT(EXTENT_FLAG_LOGGING),
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/* Filling in a preallocated extent */
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ENUM_BIT(EXTENT_FLAG_FILLING),
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/* This em is merged from two or more physically adjacent ems */
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ENUM_BIT(EXTENT_FLAG_MERGED),
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};
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/*
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* Keep this structure as compact as possible, as we can have really large
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* amounts of allocated extent maps at any time.
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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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u32 flags;
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refcount_t refs;
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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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struct btrfs_inode;
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static inline void extent_map_set_compression(struct extent_map *em,
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enum btrfs_compression_type type)
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{
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if (type == BTRFS_COMPRESS_ZLIB)
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em->flags |= EXTENT_FLAG_COMPRESS_ZLIB;
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else if (type == BTRFS_COMPRESS_LZO)
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em->flags |= EXTENT_FLAG_COMPRESS_LZO;
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else if (type == BTRFS_COMPRESS_ZSTD)
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em->flags |= EXTENT_FLAG_COMPRESS_ZSTD;
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}
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static inline enum btrfs_compression_type extent_map_compression(const struct extent_map *em)
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{
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if (em->flags & EXTENT_FLAG_COMPRESS_ZLIB)
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return BTRFS_COMPRESS_ZLIB;
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if (em->flags & EXTENT_FLAG_COMPRESS_LZO)
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return BTRFS_COMPRESS_LZO;
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if (em->flags & EXTENT_FLAG_COMPRESS_ZSTD)
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return BTRFS_COMPRESS_ZSTD;
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return BTRFS_COMPRESS_NONE;
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}
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/*
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* More efficient way to determine if extent is compressed, instead of using
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* 'extent_map_compression() != BTRFS_COMPRESS_NONE'.
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*/
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static inline bool extent_map_is_compressed(const struct extent_map *em)
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{
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return (em->flags & (EXTENT_FLAG_COMPRESS_ZLIB |
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EXTENT_FLAG_COMPRESS_LZO |
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EXTENT_FLAG_COMPRESS_ZSTD)) != 0;
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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(const 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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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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void remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em);
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int split_extent_map(struct btrfs_inode *inode, u64 start, u64 len, u64 pre,
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u64 new_logical);
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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 btrfs_inode *inode, 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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void btrfs_drop_extent_map_range(struct btrfs_inode *inode,
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u64 start, u64 end,
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bool skip_pinned);
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int btrfs_replace_extent_map_range(struct btrfs_inode *inode,
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struct extent_map *new_em,
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bool modified);
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#endif
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