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![Josef Bacik](/assets/img/avatar_default.png)
We use the modified list to keep track of which extents have been modified so we know which ones are candidates for logging at fsync() time. Newly modified extents are added to the list at modification time, around the same time the ordered extent is created. We do this so that we don't have to wait for ordered extents to complete before we know what we need to log. The problem is when something like this happens log extent 0-4k on inode 1 copy csum for 0-4k from ordered extent into log sync log commit transaction log some other extent on inode 1 ordered extent for 0-4k completes and adds itself onto modified list again log changed extents see ordered extent for 0-4k has already been logged at this point we assume the csum has been copied sync log crash On replay we will see the extent 0-4k in the log, drop the original 0-4k extent which is the same one that we are replaying which also drops the csum, and then we won't find the csum in the log for that bytenr. This of course causes us to have errors about not having csums for certain ranges of our inode. So remove the modified list manipulation in unpin_extent_cache, any modified extents should have been added well before now, and we don't want them re-logged. This fixes my test that I could reliably reproduce this problem with. Thanks, cc: stable@vger.kernel.org Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
455 lines
12 KiB
C
455 lines
12 KiB
C
#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/hardirq.h>
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#include "ctree.h"
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#include "extent_map.h"
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static struct kmem_cache *extent_map_cache;
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int __init extent_map_init(void)
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{
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extent_map_cache = kmem_cache_create("btrfs_extent_map",
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sizeof(struct extent_map), 0,
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SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
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if (!extent_map_cache)
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return -ENOMEM;
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return 0;
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}
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void extent_map_exit(void)
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{
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if (extent_map_cache)
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kmem_cache_destroy(extent_map_cache);
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}
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/**
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* extent_map_tree_init - initialize extent map tree
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* @tree: tree to initialize
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*
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* Initialize the extent tree @tree. Should be called for each new inode
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* or other user of the extent_map interface.
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*/
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void extent_map_tree_init(struct extent_map_tree *tree)
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{
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tree->map = RB_ROOT;
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INIT_LIST_HEAD(&tree->modified_extents);
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rwlock_init(&tree->lock);
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}
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/**
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* alloc_extent_map - allocate new extent map structure
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*
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* Allocate a new extent_map structure. The new structure is
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* returned with a reference count of one and needs to be
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* freed using free_extent_map()
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*/
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struct extent_map *alloc_extent_map(void)
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{
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struct extent_map *em;
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em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
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if (!em)
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return NULL;
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RB_CLEAR_NODE(&em->rb_node);
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em->flags = 0;
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em->compress_type = BTRFS_COMPRESS_NONE;
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em->generation = 0;
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atomic_set(&em->refs, 1);
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INIT_LIST_HEAD(&em->list);
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return em;
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}
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/**
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* free_extent_map - drop reference count of an extent_map
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* @em: extent map beeing releasead
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*
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* Drops the reference out on @em by one and free the structure
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* if the reference count hits zero.
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*/
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void free_extent_map(struct extent_map *em)
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{
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if (!em)
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return;
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WARN_ON(atomic_read(&em->refs) == 0);
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if (atomic_dec_and_test(&em->refs)) {
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WARN_ON(extent_map_in_tree(em));
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WARN_ON(!list_empty(&em->list));
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if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
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kfree(em->bdev);
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kmem_cache_free(extent_map_cache, em);
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}
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}
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/* simple helper to do math around the end of an extent, handling wrap */
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static u64 range_end(u64 start, u64 len)
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{
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if (start + len < start)
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return (u64)-1;
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return start + len;
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}
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static int tree_insert(struct rb_root *root, struct extent_map *em)
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{
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struct rb_node **p = &root->rb_node;
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struct rb_node *parent = NULL;
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struct extent_map *entry = NULL;
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struct rb_node *orig_parent = NULL;
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u64 end = range_end(em->start, em->len);
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while (*p) {
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parent = *p;
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entry = rb_entry(parent, struct extent_map, rb_node);
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if (em->start < entry->start)
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p = &(*p)->rb_left;
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else if (em->start >= extent_map_end(entry))
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p = &(*p)->rb_right;
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else
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return -EEXIST;
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}
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orig_parent = parent;
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while (parent && em->start >= extent_map_end(entry)) {
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parent = rb_next(parent);
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entry = rb_entry(parent, struct extent_map, rb_node);
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}
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if (parent)
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if (end > entry->start && em->start < extent_map_end(entry))
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return -EEXIST;
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parent = orig_parent;
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entry = rb_entry(parent, struct extent_map, rb_node);
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while (parent && em->start < entry->start) {
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parent = rb_prev(parent);
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entry = rb_entry(parent, struct extent_map, rb_node);
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}
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if (parent)
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if (end > entry->start && em->start < extent_map_end(entry))
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return -EEXIST;
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rb_link_node(&em->rb_node, orig_parent, p);
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rb_insert_color(&em->rb_node, root);
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return 0;
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}
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/*
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* search through the tree for an extent_map with a given offset. If
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* it can't be found, try to find some neighboring extents
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*/
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static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
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struct rb_node **prev_ret,
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struct rb_node **next_ret)
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{
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struct rb_node *n = root->rb_node;
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struct rb_node *prev = NULL;
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struct rb_node *orig_prev = NULL;
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struct extent_map *entry;
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struct extent_map *prev_entry = NULL;
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while (n) {
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entry = rb_entry(n, struct extent_map, rb_node);
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prev = n;
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prev_entry = entry;
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if (offset < entry->start)
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n = n->rb_left;
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else if (offset >= extent_map_end(entry))
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n = n->rb_right;
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else
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return n;
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}
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if (prev_ret) {
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orig_prev = prev;
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while (prev && offset >= extent_map_end(prev_entry)) {
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prev = rb_next(prev);
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prev_entry = rb_entry(prev, struct extent_map, rb_node);
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}
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*prev_ret = prev;
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prev = orig_prev;
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}
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if (next_ret) {
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prev_entry = rb_entry(prev, struct extent_map, rb_node);
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while (prev && offset < prev_entry->start) {
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prev = rb_prev(prev);
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prev_entry = rb_entry(prev, struct extent_map, rb_node);
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}
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*next_ret = prev;
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}
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return NULL;
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}
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/* check to see if two extent_map structs are adjacent and safe to merge */
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static int mergable_maps(struct extent_map *prev, struct extent_map *next)
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{
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if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
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return 0;
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/*
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* don't merge compressed extents, we need to know their
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* actual size
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*/
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if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
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return 0;
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if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) ||
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test_bit(EXTENT_FLAG_LOGGING, &next->flags))
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return 0;
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/*
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* We don't want to merge stuff that hasn't been written to the log yet
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* since it may not reflect exactly what is on disk, and that would be
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* bad.
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*/
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if (!list_empty(&prev->list) || !list_empty(&next->list))
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return 0;
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if (extent_map_end(prev) == next->start &&
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prev->flags == next->flags &&
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prev->bdev == next->bdev &&
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((next->block_start == EXTENT_MAP_HOLE &&
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prev->block_start == EXTENT_MAP_HOLE) ||
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(next->block_start == EXTENT_MAP_INLINE &&
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prev->block_start == EXTENT_MAP_INLINE) ||
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(next->block_start == EXTENT_MAP_DELALLOC &&
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prev->block_start == EXTENT_MAP_DELALLOC) ||
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(next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
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next->block_start == extent_map_block_end(prev)))) {
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return 1;
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}
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return 0;
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}
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static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
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{
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struct extent_map *merge = NULL;
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struct rb_node *rb;
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if (em->start != 0) {
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rb = rb_prev(&em->rb_node);
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if (rb)
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merge = rb_entry(rb, struct extent_map, rb_node);
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if (rb && mergable_maps(merge, em)) {
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em->start = merge->start;
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em->orig_start = merge->orig_start;
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em->len += merge->len;
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em->block_len += merge->block_len;
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em->block_start = merge->block_start;
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em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
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em->mod_start = merge->mod_start;
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em->generation = max(em->generation, merge->generation);
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rb_erase(&merge->rb_node, &tree->map);
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RB_CLEAR_NODE(&merge->rb_node);
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free_extent_map(merge);
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}
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}
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rb = rb_next(&em->rb_node);
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if (rb)
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merge = rb_entry(rb, struct extent_map, rb_node);
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if (rb && mergable_maps(em, merge)) {
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em->len += merge->len;
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em->block_len += merge->block_len;
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rb_erase(&merge->rb_node, &tree->map);
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RB_CLEAR_NODE(&merge->rb_node);
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em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
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em->generation = max(em->generation, merge->generation);
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free_extent_map(merge);
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}
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}
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/**
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* unpin_extent_cache - unpin an extent from the cache
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* @tree: tree to unpin the extent in
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* @start: logical offset in the file
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* @len: length of the extent
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* @gen: generation that this extent has been modified in
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*
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* Called after an extent has been written to disk properly. Set the generation
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* to the generation that actually added the file item to the inode so we know
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* we need to sync this extent when we call fsync().
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*/
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int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
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u64 gen)
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{
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int ret = 0;
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struct extent_map *em;
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bool prealloc = false;
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write_lock(&tree->lock);
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em = lookup_extent_mapping(tree, start, len);
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WARN_ON(!em || em->start != start);
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if (!em)
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goto out;
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em->generation = gen;
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clear_bit(EXTENT_FLAG_PINNED, &em->flags);
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em->mod_start = em->start;
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em->mod_len = em->len;
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if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
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prealloc = true;
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clear_bit(EXTENT_FLAG_FILLING, &em->flags);
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}
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try_merge_map(tree, em);
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if (prealloc) {
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em->mod_start = em->start;
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em->mod_len = em->len;
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}
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free_extent_map(em);
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out:
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write_unlock(&tree->lock);
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return ret;
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}
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void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
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{
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clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
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if (extent_map_in_tree(em))
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try_merge_map(tree, em);
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}
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static inline void setup_extent_mapping(struct extent_map_tree *tree,
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struct extent_map *em,
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int modified)
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{
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atomic_inc(&em->refs);
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em->mod_start = em->start;
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em->mod_len = em->len;
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if (modified)
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list_move(&em->list, &tree->modified_extents);
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else
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try_merge_map(tree, em);
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}
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/**
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* add_extent_mapping - add new extent map to the extent tree
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* @tree: tree to insert new map in
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* @em: map to insert
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*
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* Insert @em into @tree or perform a simple forward/backward merge with
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* existing mappings. The extent_map struct passed in will be inserted
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* into the tree directly, with an additional reference taken, or a
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* reference dropped if the merge attempt was successful.
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*/
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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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{
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int ret = 0;
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ret = tree_insert(&tree->map, em);
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if (ret)
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goto out;
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setup_extent_mapping(tree, em, modified);
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out:
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return ret;
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}
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static struct extent_map *
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__lookup_extent_mapping(struct extent_map_tree *tree,
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u64 start, u64 len, int strict)
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{
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struct extent_map *em;
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struct rb_node *rb_node;
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struct rb_node *prev = NULL;
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struct rb_node *next = NULL;
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u64 end = range_end(start, len);
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rb_node = __tree_search(&tree->map, start, &prev, &next);
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if (!rb_node) {
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if (prev)
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rb_node = prev;
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else if (next)
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rb_node = next;
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else
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return NULL;
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}
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em = rb_entry(rb_node, struct extent_map, rb_node);
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if (strict && !(end > em->start && start < extent_map_end(em)))
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return NULL;
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atomic_inc(&em->refs);
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return em;
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}
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/**
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* lookup_extent_mapping - lookup extent_map
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* @tree: tree to lookup in
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* @start: byte offset to start the search
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* @len: length of the lookup range
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*
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* Find and return the first extent_map struct in @tree that intersects the
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* [start, len] range. There may be additional objects in the tree that
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* intersect, so check the object returned carefully to make sure that no
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* additional lookups are needed.
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*/
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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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{
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return __lookup_extent_mapping(tree, start, len, 1);
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}
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/**
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* search_extent_mapping - find a nearby extent map
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* @tree: tree to lookup in
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* @start: byte offset to start the search
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* @len: length of the lookup range
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*
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* Find and return the first extent_map struct in @tree that intersects the
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* [start, len] range.
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*
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* If one can't be found, any nearby extent may be returned
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*/
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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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{
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return __lookup_extent_mapping(tree, start, len, 0);
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}
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/**
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* remove_extent_mapping - removes an extent_map from the extent tree
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* @tree: extent tree to remove from
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* @em: extent map beeing removed
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*
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* Removes @em from @tree. No reference counts are dropped, and no checks
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* are done to see if the range is in use
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*/
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int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
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{
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int ret = 0;
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WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
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rb_erase(&em->rb_node, &tree->map);
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if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
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list_del_init(&em->list);
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RB_CLEAR_NODE(&em->rb_node);
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return ret;
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}
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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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{
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WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags));
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ASSERT(extent_map_in_tree(cur));
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if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags))
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list_del_init(&cur->list);
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rb_replace_node(&cur->rb_node, &new->rb_node, &tree->map);
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RB_CLEAR_NODE(&cur->rb_node);
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setup_extent_mapping(tree, new, modified);
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}
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