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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /fs/btrfs/extent_map.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/btrfs/extent_map.c')
-rw-r--r--fs/btrfs/extent_map.c1053
1 files changed, 1053 insertions, 0 deletions
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
new file mode 100644
index 0000000000..a6d8368ed0
--- /dev/null
+++ b/fs/btrfs/extent_map.c
@@ -0,0 +1,1053 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include "messages.h"
+#include "ctree.h"
+#include "volumes.h"
+#include "extent_map.h"
+#include "compression.h"
+#include "btrfs_inode.h"
+
+
+static struct kmem_cache *extent_map_cache;
+
+int __init extent_map_init(void)
+{
+ extent_map_cache = kmem_cache_create("btrfs_extent_map",
+ sizeof(struct extent_map), 0,
+ SLAB_MEM_SPREAD, NULL);
+ if (!extent_map_cache)
+ return -ENOMEM;
+ return 0;
+}
+
+void __cold extent_map_exit(void)
+{
+ kmem_cache_destroy(extent_map_cache);
+}
+
+/*
+ * Initialize the extent tree @tree. Should be called for each new inode or
+ * other user of the extent_map interface.
+ */
+void extent_map_tree_init(struct extent_map_tree *tree)
+{
+ tree->map = RB_ROOT_CACHED;
+ INIT_LIST_HEAD(&tree->modified_extents);
+ rwlock_init(&tree->lock);
+}
+
+/*
+ * Allocate a new extent_map structure. The new structure is returned with a
+ * reference count of one and needs to be freed using free_extent_map()
+ */
+struct extent_map *alloc_extent_map(void)
+{
+ struct extent_map *em;
+ em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
+ if (!em)
+ return NULL;
+ RB_CLEAR_NODE(&em->rb_node);
+ em->compress_type = BTRFS_COMPRESS_NONE;
+ refcount_set(&em->refs, 1);
+ INIT_LIST_HEAD(&em->list);
+ return em;
+}
+
+/*
+ * Drop the reference out on @em by one and free the structure if the reference
+ * count hits zero.
+ */
+void free_extent_map(struct extent_map *em)
+{
+ if (!em)
+ return;
+ if (refcount_dec_and_test(&em->refs)) {
+ WARN_ON(extent_map_in_tree(em));
+ WARN_ON(!list_empty(&em->list));
+ if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
+ kfree(em->map_lookup);
+ kmem_cache_free(extent_map_cache, em);
+ }
+}
+
+/* Do the math around the end of an extent, handling wrapping. */
+static u64 range_end(u64 start, u64 len)
+{
+ if (start + len < start)
+ return (u64)-1;
+ return start + len;
+}
+
+static int tree_insert(struct rb_root_cached *root, struct extent_map *em)
+{
+ struct rb_node **p = &root->rb_root.rb_node;
+ struct rb_node *parent = NULL;
+ struct extent_map *entry = NULL;
+ struct rb_node *orig_parent = NULL;
+ u64 end = range_end(em->start, em->len);
+ bool leftmost = true;
+
+ while (*p) {
+ parent = *p;
+ entry = rb_entry(parent, struct extent_map, rb_node);
+
+ if (em->start < entry->start) {
+ p = &(*p)->rb_left;
+ } else if (em->start >= extent_map_end(entry)) {
+ p = &(*p)->rb_right;
+ leftmost = false;
+ } else {
+ return -EEXIST;
+ }
+ }
+
+ orig_parent = parent;
+ while (parent && em->start >= extent_map_end(entry)) {
+ parent = rb_next(parent);
+ entry = rb_entry(parent, struct extent_map, rb_node);
+ }
+ if (parent)
+ if (end > entry->start && em->start < extent_map_end(entry))
+ return -EEXIST;
+
+ parent = orig_parent;
+ entry = rb_entry(parent, struct extent_map, rb_node);
+ while (parent && em->start < entry->start) {
+ parent = rb_prev(parent);
+ entry = rb_entry(parent, struct extent_map, rb_node);
+ }
+ if (parent)
+ if (end > entry->start && em->start < extent_map_end(entry))
+ return -EEXIST;
+
+ rb_link_node(&em->rb_node, orig_parent, p);
+ rb_insert_color_cached(&em->rb_node, root, leftmost);
+ return 0;
+}
+
+/*
+ * Search through the tree for an extent_map with a given offset. If it can't
+ * be found, try to find some neighboring extents
+ */
+static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
+ struct rb_node **prev_or_next_ret)
+{
+ struct rb_node *n = root->rb_node;
+ struct rb_node *prev = NULL;
+ struct rb_node *orig_prev = NULL;
+ struct extent_map *entry;
+ struct extent_map *prev_entry = NULL;
+
+ ASSERT(prev_or_next_ret);
+
+ while (n) {
+ entry = rb_entry(n, struct extent_map, rb_node);
+ prev = n;
+ prev_entry = entry;
+
+ if (offset < entry->start)
+ n = n->rb_left;
+ else if (offset >= extent_map_end(entry))
+ n = n->rb_right;
+ else
+ return n;
+ }
+
+ orig_prev = prev;
+ while (prev && offset >= extent_map_end(prev_entry)) {
+ prev = rb_next(prev);
+ prev_entry = rb_entry(prev, struct extent_map, rb_node);
+ }
+
+ /*
+ * Previous extent map found, return as in this case the caller does not
+ * care about the next one.
+ */
+ if (prev) {
+ *prev_or_next_ret = prev;
+ return NULL;
+ }
+
+ prev = orig_prev;
+ prev_entry = rb_entry(prev, struct extent_map, rb_node);
+ while (prev && offset < prev_entry->start) {
+ prev = rb_prev(prev);
+ prev_entry = rb_entry(prev, struct extent_map, rb_node);
+ }
+ *prev_or_next_ret = prev;
+
+ return NULL;
+}
+
+/* Check to see if two extent_map structs are adjacent and safe to merge. */
+static int mergable_maps(struct extent_map *prev, struct extent_map *next)
+{
+ if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
+ return 0;
+
+ /*
+ * don't merge compressed extents, we need to know their
+ * actual size
+ */
+ if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
+ return 0;
+
+ if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) ||
+ test_bit(EXTENT_FLAG_LOGGING, &next->flags))
+ return 0;
+
+ /*
+ * We don't want to merge stuff that hasn't been written to the log yet
+ * since it may not reflect exactly what is on disk, and that would be
+ * bad.
+ */
+ if (!list_empty(&prev->list) || !list_empty(&next->list))
+ return 0;
+
+ ASSERT(next->block_start != EXTENT_MAP_DELALLOC &&
+ prev->block_start != EXTENT_MAP_DELALLOC);
+
+ if (prev->map_lookup || next->map_lookup)
+ ASSERT(test_bit(EXTENT_FLAG_FS_MAPPING, &prev->flags) &&
+ test_bit(EXTENT_FLAG_FS_MAPPING, &next->flags));
+
+ if (extent_map_end(prev) == next->start &&
+ prev->flags == next->flags &&
+ prev->map_lookup == next->map_lookup &&
+ ((next->block_start == EXTENT_MAP_HOLE &&
+ prev->block_start == EXTENT_MAP_HOLE) ||
+ (next->block_start == EXTENT_MAP_INLINE &&
+ prev->block_start == EXTENT_MAP_INLINE) ||
+ (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
+ next->block_start == extent_map_block_end(prev)))) {
+ return 1;
+ }
+ return 0;
+}
+
+static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
+{
+ struct extent_map *merge = NULL;
+ struct rb_node *rb;
+
+ /*
+ * We can't modify an extent map that is in the tree and that is being
+ * used by another task, as it can cause that other task to see it in
+ * inconsistent state during the merging. We always have 1 reference for
+ * the tree and 1 for this task (which is unpinning the extent map or
+ * clearing the logging flag), so anything > 2 means it's being used by
+ * other tasks too.
+ */
+ if (refcount_read(&em->refs) > 2)
+ return;
+
+ if (em->start != 0) {
+ rb = rb_prev(&em->rb_node);
+ if (rb)
+ merge = rb_entry(rb, struct extent_map, rb_node);
+ if (rb && mergable_maps(merge, em)) {
+ em->start = merge->start;
+ em->orig_start = merge->orig_start;
+ em->len += merge->len;
+ em->block_len += merge->block_len;
+ em->block_start = merge->block_start;
+ em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
+ em->mod_start = merge->mod_start;
+ em->generation = max(em->generation, merge->generation);
+ set_bit(EXTENT_FLAG_MERGED, &em->flags);
+
+ rb_erase_cached(&merge->rb_node, &tree->map);
+ RB_CLEAR_NODE(&merge->rb_node);
+ free_extent_map(merge);
+ }
+ }
+
+ rb = rb_next(&em->rb_node);
+ if (rb)
+ merge = rb_entry(rb, struct extent_map, rb_node);
+ if (rb && mergable_maps(em, merge)) {
+ em->len += merge->len;
+ em->block_len += merge->block_len;
+ rb_erase_cached(&merge->rb_node, &tree->map);
+ RB_CLEAR_NODE(&merge->rb_node);
+ em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
+ em->generation = max(em->generation, merge->generation);
+ set_bit(EXTENT_FLAG_MERGED, &em->flags);
+ free_extent_map(merge);
+ }
+}
+
+/*
+ * Unpin an extent from the cache.
+ *
+ * @tree: tree to unpin the extent in
+ * @start: logical offset in the file
+ * @len: length of the extent
+ * @gen: generation that this extent has been modified in
+ *
+ * Called after an extent has been written to disk properly. Set the generation
+ * to the generation that actually added the file item to the inode so we know
+ * we need to sync this extent when we call fsync().
+ */
+int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
+ u64 gen)
+{
+ int ret = 0;
+ struct extent_map *em;
+ bool prealloc = false;
+
+ write_lock(&tree->lock);
+ em = lookup_extent_mapping(tree, start, len);
+
+ WARN_ON(!em || em->start != start);
+
+ if (!em)
+ goto out;
+
+ em->generation = gen;
+ clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+ em->mod_start = em->start;
+ em->mod_len = em->len;
+
+ if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
+ prealloc = true;
+ clear_bit(EXTENT_FLAG_FILLING, &em->flags);
+ }
+
+ try_merge_map(tree, em);
+
+ if (prealloc) {
+ em->mod_start = em->start;
+ em->mod_len = em->len;
+ }
+
+ free_extent_map(em);
+out:
+ write_unlock(&tree->lock);
+ return ret;
+
+}
+
+void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
+{
+ lockdep_assert_held_write(&tree->lock);
+
+ clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
+ if (extent_map_in_tree(em))
+ try_merge_map(tree, em);
+}
+
+static inline void setup_extent_mapping(struct extent_map_tree *tree,
+ struct extent_map *em,
+ int modified)
+{
+ refcount_inc(&em->refs);
+ em->mod_start = em->start;
+ em->mod_len = em->len;
+
+ if (modified)
+ list_move(&em->list, &tree->modified_extents);
+ else
+ try_merge_map(tree, em);
+}
+
+static void extent_map_device_set_bits(struct extent_map *em, unsigned bits)
+{
+ struct map_lookup *map = em->map_lookup;
+ u64 stripe_size = em->orig_block_len;
+ int i;
+
+ for (i = 0; i < map->num_stripes; i++) {
+ struct btrfs_io_stripe *stripe = &map->stripes[i];
+ struct btrfs_device *device = stripe->dev;
+
+ set_extent_bit(&device->alloc_state, stripe->physical,
+ stripe->physical + stripe_size - 1,
+ bits | EXTENT_NOWAIT, NULL);
+ }
+}
+
+static void extent_map_device_clear_bits(struct extent_map *em, unsigned bits)
+{
+ struct map_lookup *map = em->map_lookup;
+ u64 stripe_size = em->orig_block_len;
+ int i;
+
+ for (i = 0; i < map->num_stripes; i++) {
+ struct btrfs_io_stripe *stripe = &map->stripes[i];
+ struct btrfs_device *device = stripe->dev;
+
+ __clear_extent_bit(&device->alloc_state, stripe->physical,
+ stripe->physical + stripe_size - 1,
+ bits | EXTENT_NOWAIT,
+ NULL, NULL);
+ }
+}
+
+/*
+ * Add new extent map to the extent tree
+ *
+ * @tree: tree to insert new map in
+ * @em: map to insert
+ * @modified: indicate whether the given @em should be added to the
+ * modified list, which indicates the extent needs to be logged
+ *
+ * Insert @em into @tree or perform a simple forward/backward merge with
+ * existing mappings. The extent_map struct passed in will be inserted
+ * into the tree directly, with an additional reference taken, or a
+ * reference dropped if the merge attempt was successful.
+ */
+int add_extent_mapping(struct extent_map_tree *tree,
+ struct extent_map *em, int modified)
+{
+ int ret = 0;
+
+ lockdep_assert_held_write(&tree->lock);
+
+ ret = tree_insert(&tree->map, em);
+ if (ret)
+ goto out;
+
+ setup_extent_mapping(tree, em, modified);
+ if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags)) {
+ extent_map_device_set_bits(em, CHUNK_ALLOCATED);
+ extent_map_device_clear_bits(em, CHUNK_TRIMMED);
+ }
+out:
+ return ret;
+}
+
+static struct extent_map *
+__lookup_extent_mapping(struct extent_map_tree *tree,
+ u64 start, u64 len, int strict)
+{
+ struct extent_map *em;
+ struct rb_node *rb_node;
+ struct rb_node *prev_or_next = NULL;
+ u64 end = range_end(start, len);
+
+ rb_node = __tree_search(&tree->map.rb_root, start, &prev_or_next);
+ if (!rb_node) {
+ if (prev_or_next)
+ rb_node = prev_or_next;
+ else
+ return NULL;
+ }
+
+ em = rb_entry(rb_node, struct extent_map, rb_node);
+
+ if (strict && !(end > em->start && start < extent_map_end(em)))
+ return NULL;
+
+ refcount_inc(&em->refs);
+ return em;
+}
+
+/*
+ * Lookup extent_map that intersects @start + @len range.
+ *
+ * @tree: tree to lookup in
+ * @start: byte offset to start the search
+ * @len: length of the lookup range
+ *
+ * Find and return the first extent_map struct in @tree that intersects the
+ * [start, len] range. There may be additional objects in the tree that
+ * intersect, so check the object returned carefully to make sure that no
+ * additional lookups are needed.
+ */
+struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
+ u64 start, u64 len)
+{
+ return __lookup_extent_mapping(tree, start, len, 1);
+}
+
+/*
+ * Find a nearby extent map intersecting @start + @len (not an exact search).
+ *
+ * @tree: tree to lookup in
+ * @start: byte offset to start the search
+ * @len: length of the lookup range
+ *
+ * Find and return the first extent_map struct in @tree that intersects the
+ * [start, len] range.
+ *
+ * If one can't be found, any nearby extent may be returned
+ */
+struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
+ u64 start, u64 len)
+{
+ return __lookup_extent_mapping(tree, start, len, 0);
+}
+
+/*
+ * Remove an extent_map from the extent tree.
+ *
+ * @tree: extent tree to remove from
+ * @em: extent map being removed
+ *
+ * Remove @em from @tree. No reference counts are dropped, and no checks
+ * are done to see if the range is in use.
+ */
+void remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
+{
+ lockdep_assert_held_write(&tree->lock);
+
+ WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
+ rb_erase_cached(&em->rb_node, &tree->map);
+ if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
+ list_del_init(&em->list);
+ if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
+ extent_map_device_clear_bits(em, CHUNK_ALLOCATED);
+ RB_CLEAR_NODE(&em->rb_node);
+}
+
+static void replace_extent_mapping(struct extent_map_tree *tree,
+ struct extent_map *cur,
+ struct extent_map *new,
+ int modified)
+{
+ lockdep_assert_held_write(&tree->lock);
+
+ WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags));
+ ASSERT(extent_map_in_tree(cur));
+ if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags))
+ list_del_init(&cur->list);
+ rb_replace_node_cached(&cur->rb_node, &new->rb_node, &tree->map);
+ RB_CLEAR_NODE(&cur->rb_node);
+
+ setup_extent_mapping(tree, new, modified);
+}
+
+static struct extent_map *next_extent_map(const struct extent_map *em)
+{
+ struct rb_node *next;
+
+ next = rb_next(&em->rb_node);
+ if (!next)
+ return NULL;
+ return container_of(next, struct extent_map, rb_node);
+}
+
+static struct extent_map *prev_extent_map(struct extent_map *em)
+{
+ struct rb_node *prev;
+
+ prev = rb_prev(&em->rb_node);
+ if (!prev)
+ return NULL;
+ return container_of(prev, struct extent_map, rb_node);
+}
+
+/*
+ * Helper for btrfs_get_extent. Given an existing extent in the tree,
+ * the existing extent is the nearest extent to map_start,
+ * and an extent that you want to insert, deal with overlap and insert
+ * the best fitted new extent into the tree.
+ */
+static noinline int merge_extent_mapping(struct extent_map_tree *em_tree,
+ struct extent_map *existing,
+ struct extent_map *em,
+ u64 map_start)
+{
+ struct extent_map *prev;
+ struct extent_map *next;
+ u64 start;
+ u64 end;
+ u64 start_diff;
+
+ BUG_ON(map_start < em->start || map_start >= extent_map_end(em));
+
+ if (existing->start > map_start) {
+ next = existing;
+ prev = prev_extent_map(next);
+ } else {
+ prev = existing;
+ next = next_extent_map(prev);
+ }
+
+ start = prev ? extent_map_end(prev) : em->start;
+ start = max_t(u64, start, em->start);
+ end = next ? next->start : extent_map_end(em);
+ end = min_t(u64, end, extent_map_end(em));
+ start_diff = start - em->start;
+ em->start = start;
+ em->len = end - start;
+ if (em->block_start < EXTENT_MAP_LAST_BYTE &&
+ !test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
+ em->block_start += start_diff;
+ em->block_len = em->len;
+ }
+ return add_extent_mapping(em_tree, em, 0);
+}
+
+/*
+ * Add extent mapping into em_tree.
+ *
+ * @fs_info: the filesystem
+ * @em_tree: extent tree into which we want to insert the extent mapping
+ * @em_in: extent we are inserting
+ * @start: start of the logical range btrfs_get_extent() is requesting
+ * @len: length of the logical range btrfs_get_extent() is requesting
+ *
+ * Note that @em_in's range may be different from [start, start+len),
+ * but they must be overlapped.
+ *
+ * Insert @em_in into @em_tree. In case there is an overlapping range, handle
+ * the -EEXIST by either:
+ * a) Returning the existing extent in @em_in if @start is within the
+ * existing em.
+ * b) Merge the existing extent with @em_in passed in.
+ *
+ * Return 0 on success, otherwise -EEXIST.
+ *
+ */
+int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
+ struct extent_map_tree *em_tree,
+ struct extent_map **em_in, u64 start, u64 len)
+{
+ int ret;
+ struct extent_map *em = *em_in;
+
+ /*
+ * Tree-checker should have rejected any inline extent with non-zero
+ * file offset. Here just do a sanity check.
+ */
+ if (em->block_start == EXTENT_MAP_INLINE)
+ ASSERT(em->start == 0);
+
+ ret = add_extent_mapping(em_tree, em, 0);
+ /* it is possible that someone inserted the extent into the tree
+ * while we had the lock dropped. It is also possible that
+ * an overlapping map exists in the tree
+ */
+ if (ret == -EEXIST) {
+ struct extent_map *existing;
+
+ ret = 0;
+
+ existing = search_extent_mapping(em_tree, start, len);
+
+ trace_btrfs_handle_em_exist(fs_info, existing, em, start, len);
+
+ /*
+ * existing will always be non-NULL, since there must be
+ * extent causing the -EEXIST.
+ */
+ if (start >= existing->start &&
+ start < extent_map_end(existing)) {
+ free_extent_map(em);
+ *em_in = existing;
+ ret = 0;
+ } else {
+ u64 orig_start = em->start;
+ u64 orig_len = em->len;
+
+ /*
+ * The existing extent map is the one nearest to
+ * the [start, start + len) range which overlaps
+ */
+ ret = merge_extent_mapping(em_tree, existing,
+ em, start);
+ if (ret) {
+ free_extent_map(em);
+ *em_in = NULL;
+ WARN_ONCE(ret,
+"unexpected error %d: merge existing(start %llu len %llu) with em(start %llu len %llu)\n",
+ ret, existing->start, existing->len,
+ orig_start, orig_len);
+ }
+ free_extent_map(existing);
+ }
+ }
+
+ ASSERT(ret == 0 || ret == -EEXIST);
+ return ret;
+}
+
+/*
+ * Drop all extent maps from a tree in the fastest possible way, rescheduling
+ * if needed. This avoids searching the tree, from the root down to the first
+ * extent map, before each deletion.
+ */
+static void drop_all_extent_maps_fast(struct extent_map_tree *tree)
+{
+ write_lock(&tree->lock);
+ while (!RB_EMPTY_ROOT(&tree->map.rb_root)) {
+ struct extent_map *em;
+ struct rb_node *node;
+
+ node = rb_first_cached(&tree->map);
+ em = rb_entry(node, struct extent_map, rb_node);
+ clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+ clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
+ remove_extent_mapping(tree, em);
+ free_extent_map(em);
+ cond_resched_rwlock_write(&tree->lock);
+ }
+ write_unlock(&tree->lock);
+}
+
+/*
+ * Drop all extent maps in a given range.
+ *
+ * @inode: The target inode.
+ * @start: Start offset of the range.
+ * @end: End offset of the range (inclusive value).
+ * @skip_pinned: Indicate if pinned extent maps should be ignored or not.
+ *
+ * This drops all the extent maps that intersect the given range [@start, @end].
+ * Extent maps that partially overlap the range and extend behind or beyond it,
+ * are split.
+ * The caller should have locked an appropriate file range in the inode's io
+ * tree before calling this function.
+ */
+void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end,
+ bool skip_pinned)
+{
+ struct extent_map *split;
+ struct extent_map *split2;
+ struct extent_map *em;
+ struct extent_map_tree *em_tree = &inode->extent_tree;
+ u64 len = end - start + 1;
+
+ WARN_ON(end < start);
+ if (end == (u64)-1) {
+ if (start == 0 && !skip_pinned) {
+ drop_all_extent_maps_fast(em_tree);
+ return;
+ }
+ len = (u64)-1;
+ } else {
+ /* Make end offset exclusive for use in the loop below. */
+ end++;
+ }
+
+ /*
+ * It's ok if we fail to allocate the extent maps, see the comment near
+ * the bottom of the loop below. We only need two spare extent maps in
+ * the worst case, where the first extent map that intersects our range
+ * starts before the range and the last extent map that intersects our
+ * range ends after our range (and they might be the same extent map),
+ * because we need to split those two extent maps at the boundaries.
+ */
+ split = alloc_extent_map();
+ split2 = alloc_extent_map();
+
+ write_lock(&em_tree->lock);
+ em = lookup_extent_mapping(em_tree, start, len);
+
+ while (em) {
+ /* extent_map_end() returns exclusive value (last byte + 1). */
+ const u64 em_end = extent_map_end(em);
+ struct extent_map *next_em = NULL;
+ u64 gen;
+ unsigned long flags;
+ bool modified;
+ bool compressed;
+
+ if (em_end < end) {
+ next_em = next_extent_map(em);
+ if (next_em) {
+ if (next_em->start < end)
+ refcount_inc(&next_em->refs);
+ else
+ next_em = NULL;
+ }
+ }
+
+ if (skip_pinned && test_bit(EXTENT_FLAG_PINNED, &em->flags)) {
+ start = em_end;
+ goto next;
+ }
+
+ flags = em->flags;
+ clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+ /*
+ * In case we split the extent map, we want to preserve the
+ * EXTENT_FLAG_LOGGING flag on our extent map, but we don't want
+ * it on the new extent maps.
+ */
+ clear_bit(EXTENT_FLAG_LOGGING, &flags);
+ modified = !list_empty(&em->list);
+
+ /*
+ * The extent map does not cross our target range, so no need to
+ * split it, we can remove it directly.
+ */
+ if (em->start >= start && em_end <= end)
+ goto remove_em;
+
+ gen = em->generation;
+ compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
+
+ if (em->start < start) {
+ if (!split) {
+ split = split2;
+ split2 = NULL;
+ if (!split)
+ goto remove_em;
+ }
+ split->start = em->start;
+ split->len = start - em->start;
+
+ if (em->block_start < EXTENT_MAP_LAST_BYTE) {
+ split->orig_start = em->orig_start;
+ split->block_start = em->block_start;
+
+ if (compressed)
+ split->block_len = em->block_len;
+ else
+ split->block_len = split->len;
+ split->orig_block_len = max(split->block_len,
+ em->orig_block_len);
+ split->ram_bytes = em->ram_bytes;
+ } else {
+ split->orig_start = split->start;
+ split->block_len = 0;
+ split->block_start = em->block_start;
+ split->orig_block_len = 0;
+ split->ram_bytes = split->len;
+ }
+
+ split->generation = gen;
+ split->flags = flags;
+ split->compress_type = em->compress_type;
+ replace_extent_mapping(em_tree, em, split, modified);
+ free_extent_map(split);
+ split = split2;
+ split2 = NULL;
+ }
+ if (em_end > end) {
+ if (!split) {
+ split = split2;
+ split2 = NULL;
+ if (!split)
+ goto remove_em;
+ }
+ split->start = end;
+ split->len = em_end - end;
+ split->block_start = em->block_start;
+ split->flags = flags;
+ split->compress_type = em->compress_type;
+ split->generation = gen;
+
+ if (em->block_start < EXTENT_MAP_LAST_BYTE) {
+ split->orig_block_len = max(em->block_len,
+ em->orig_block_len);
+
+ split->ram_bytes = em->ram_bytes;
+ if (compressed) {
+ split->block_len = em->block_len;
+ split->orig_start = em->orig_start;
+ } else {
+ const u64 diff = start + len - em->start;
+
+ split->block_len = split->len;
+ split->block_start += diff;
+ split->orig_start = em->orig_start;
+ }
+ } else {
+ split->ram_bytes = split->len;
+ split->orig_start = split->start;
+ split->block_len = 0;
+ split->orig_block_len = 0;
+ }
+
+ if (extent_map_in_tree(em)) {
+ replace_extent_mapping(em_tree, em, split,
+ modified);
+ } else {
+ int ret;
+
+ ret = add_extent_mapping(em_tree, split,
+ modified);
+ /* Logic error, shouldn't happen. */
+ ASSERT(ret == 0);
+ if (WARN_ON(ret != 0) && modified)
+ btrfs_set_inode_full_sync(inode);
+ }
+ free_extent_map(split);
+ split = NULL;
+ }
+remove_em:
+ if (extent_map_in_tree(em)) {
+ /*
+ * If the extent map is still in the tree it means that
+ * either of the following is true:
+ *
+ * 1) It fits entirely in our range (doesn't end beyond
+ * it or starts before it);
+ *
+ * 2) It starts before our range and/or ends after our
+ * range, and we were not able to allocate the extent
+ * maps for split operations, @split and @split2.
+ *
+ * If we are at case 2) then we just remove the entire
+ * extent map - this is fine since if anyone needs it to
+ * access the subranges outside our range, will just
+ * load it again from the subvolume tree's file extent
+ * item. However if the extent map was in the list of
+ * modified extents, then we must mark the inode for a
+ * full fsync, otherwise a fast fsync will miss this
+ * extent if it's new and needs to be logged.
+ */
+ if ((em->start < start || em_end > end) && modified) {
+ ASSERT(!split);
+ btrfs_set_inode_full_sync(inode);
+ }
+ remove_extent_mapping(em_tree, em);
+ }
+
+ /*
+ * Once for the tree reference (we replaced or removed the
+ * extent map from the tree).
+ */
+ free_extent_map(em);
+next:
+ /* Once for us (for our lookup reference). */
+ free_extent_map(em);
+
+ em = next_em;
+ }
+
+ write_unlock(&em_tree->lock);
+
+ free_extent_map(split);
+ free_extent_map(split2);
+}
+
+/*
+ * Replace a range in the inode's extent map tree with a new extent map.
+ *
+ * @inode: The target inode.
+ * @new_em: The new extent map to add to the inode's extent map tree.
+ * @modified: Indicate if the new extent map should be added to the list of
+ * modified extents (for fast fsync tracking).
+ *
+ * Drops all the extent maps in the inode's extent map tree that intersect the
+ * range of the new extent map and adds the new extent map to the tree.
+ * The caller should have locked an appropriate file range in the inode's io
+ * tree before calling this function.
+ */
+int btrfs_replace_extent_map_range(struct btrfs_inode *inode,
+ struct extent_map *new_em,
+ bool modified)
+{
+ const u64 end = new_em->start + new_em->len - 1;
+ struct extent_map_tree *tree = &inode->extent_tree;
+ int ret;
+
+ ASSERT(!extent_map_in_tree(new_em));
+
+ /*
+ * The caller has locked an appropriate file range in the inode's io
+ * tree, but getting -EEXIST when adding the new extent map can still
+ * happen in case there are extents that partially cover the range, and
+ * this is due to two tasks operating on different parts of the extent.
+ * See commit 18e83ac75bfe67 ("Btrfs: fix unexpected EEXIST from
+ * btrfs_get_extent") for an example and details.
+ */
+ do {
+ btrfs_drop_extent_map_range(inode, new_em->start, end, false);
+ write_lock(&tree->lock);
+ ret = add_extent_mapping(tree, new_em, modified);
+ write_unlock(&tree->lock);
+ } while (ret == -EEXIST);
+
+ return ret;
+}
+
+/*
+ * Split off the first pre bytes from the extent_map at [start, start + len],
+ * and set the block_start for it to new_logical.
+ *
+ * This function is used when an ordered_extent needs to be split.
+ */
+int split_extent_map(struct btrfs_inode *inode, u64 start, u64 len, u64 pre,
+ u64 new_logical)
+{
+ struct extent_map_tree *em_tree = &inode->extent_tree;
+ struct extent_map *em;
+ struct extent_map *split_pre = NULL;
+ struct extent_map *split_mid = NULL;
+ int ret = 0;
+ unsigned long flags;
+
+ ASSERT(pre != 0);
+ ASSERT(pre < len);
+
+ split_pre = alloc_extent_map();
+ if (!split_pre)
+ return -ENOMEM;
+ split_mid = alloc_extent_map();
+ if (!split_mid) {
+ ret = -ENOMEM;
+ goto out_free_pre;
+ }
+
+ lock_extent(&inode->io_tree, start, start + len - 1, NULL);
+ write_lock(&em_tree->lock);
+ em = lookup_extent_mapping(em_tree, start, len);
+ if (!em) {
+ ret = -EIO;
+ goto out_unlock;
+ }
+
+ ASSERT(em->len == len);
+ ASSERT(!test_bit(EXTENT_FLAG_COMPRESSED, &em->flags));
+ ASSERT(em->block_start < EXTENT_MAP_LAST_BYTE);
+ ASSERT(test_bit(EXTENT_FLAG_PINNED, &em->flags));
+ ASSERT(!test_bit(EXTENT_FLAG_LOGGING, &em->flags));
+ ASSERT(!list_empty(&em->list));
+
+ flags = em->flags;
+ clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+
+ /* First, replace the em with a new extent_map starting from * em->start */
+ split_pre->start = em->start;
+ split_pre->len = pre;
+ split_pre->orig_start = split_pre->start;
+ split_pre->block_start = new_logical;
+ split_pre->block_len = split_pre->len;
+ split_pre->orig_block_len = split_pre->block_len;
+ split_pre->ram_bytes = split_pre->len;
+ split_pre->flags = flags;
+ split_pre->compress_type = em->compress_type;
+ split_pre->generation = em->generation;
+
+ replace_extent_mapping(em_tree, em, split_pre, 1);
+
+ /*
+ * Now we only have an extent_map at:
+ * [em->start, em->start + pre]
+ */
+
+ /* Insert the middle extent_map. */
+ split_mid->start = em->start + pre;
+ split_mid->len = em->len - pre;
+ split_mid->orig_start = split_mid->start;
+ split_mid->block_start = em->block_start + pre;
+ split_mid->block_len = split_mid->len;
+ split_mid->orig_block_len = split_mid->block_len;
+ split_mid->ram_bytes = split_mid->len;
+ split_mid->flags = flags;
+ split_mid->compress_type = em->compress_type;
+ split_mid->generation = em->generation;
+ add_extent_mapping(em_tree, split_mid, 1);
+
+ /* Once for us */
+ free_extent_map(em);
+ /* Once for the tree */
+ free_extent_map(em);
+
+out_unlock:
+ write_unlock(&em_tree->lock);
+ unlock_extent(&inode->io_tree, start, start + len - 1, NULL);
+ free_extent_map(split_mid);
+out_free_pre:
+ free_extent_map(split_pre);
+ return ret;
+}