Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 985 insertions, 0 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
new file mode 100644
index 000000000..56d7580fd
--- /dev/null
+++ b/fs/btrfs/extent_map.c
@@ -0,0 +1,985 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/spinlock.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);
+}
+
+/**
+ * extent_map_tree_init - initialize extent map tree
+ * @tree:		tree to initialize
+ *
+ * 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);
+}
+
+/**
+ * alloc_extent_map - allocate new extent map structure
+ *
+ * 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;
+}
+
+/**
+ * free_extent_map - drop reference count of an extent_map
+ * @em:		extent map being released
+ *
+ * Drops 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);
+	}
+}
+
+/* simple helper to do math around the end of an extent, handling wrap */
+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_extent_cache - 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_bits_nowait(&device->alloc_state, stripe->physical,
+				 stripe->physical + stripe_size - 1, bits);
+	}
+}
+
+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,
+				   NULL, GFP_NOWAIT, 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_mapping - lookup extent_map
+ * @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);
+}
+
+/**
+ * search_extent_mapping - find a nearby extent map
+ * @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_extent_mapping - removes an extent_map from the extent tree
+ * @tree:	extent tree to remove from
+ * @em:		extent map being removed
+ *
+ * Removes @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);
+}
+
+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);
+}
+
+/*
+ * Get the extent map that immediately follows another one.
+ *
+ * @tree:       The extent map tree that the extent map belong to.
+ *              Holding read or write access on the tree's lock is required.
+ * @em:         An extent map from the given tree. The caller must ensure that
+ *              between getting @em and between calling this function, the
+ *              extent map @em is not removed from the tree - for example, by
+ *              holding the tree's lock for the duration of those 2 operations.
+ *
+ * Returns the extent map that immediately follows @em, or NULL if @em is the
+ * last extent map in the tree.
+ */
+struct extent_map *btrfs_next_extent_map(const struct extent_map_tree *tree,
+					 const struct extent_map *em)
+{
+	struct extent_map *next;
+
+	/* The lock must be acquired either in read mode or write mode. */
+	lockdep_assert_held(&tree->lock);
+	ASSERT(extent_map_in_tree(em));
+
+	next = next_extent_map(em);
+	if (next)
+		refcount_inc(&next->refs);
+
+	return next;
+}
+
+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;
+
+	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;
+}