btrfs: refactor btrfs_drop_extents() to make it easier to extend

There are many arguments for __btrfs_drop_extents() and its wrapper
btrfs_drop_extents(), which makes it hard to add more arguments to it and
requires changing every caller. I have added a couple myself back in 2014
commit 1acae57b ("Btrfs: faster file extent item replace operations")
and therefore know firsthand that it is a bit cumbersome to add additional
arguments to these functions.

Since I will need to add more arguments in a subsequent bug fix, this
change is preparatory work and adds a data structure that holds all the
arguments, for both input and output, that are passed to this function,
with some comments in the structure's definition mentioning what each
field is and how it relates to other fields.

Callers of this function need only to zero out the content of the
structure and setup only the fields they need. This also removes the
need to have both __btrfs_drop_extents() and btrfs_drop_extents(), so
now we have a single function named btrfs_drop_extents() that takes a
pointer to this new data structure (struct btrfs_drop_extents_args).
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -1233,6 +1233,58 @@ struct btrfs_replace_extent_info {
 	int insertions;
 };
 
+/* Arguments for btrfs_drop_extents() */
+struct btrfs_drop_extents_args {
+	/* Input parameters */
+
+	/*
+	 * If NULL, btrfs_drop_extents() will allocate and free its own path.
+	 * If 'replace_extent' is true, this must not be NULL. Also the path
+	 * is always released except if 'replace_extent' is true and
+	 * btrfs_drop_extents() sets 'extent_inserted' to true, in which case
+	 * the path is kept locked.
+	 */
+	struct btrfs_path *path;
+	/* Start offset of the range to drop extents from */
+	u64 start;
+	/* End (exclusive, last byte + 1) of the range to drop extents from */
+	u64 end;
+	/* If true drop all the extent maps in the range */
+	bool drop_cache;
+	/*
+	 * If true it means we want to insert a new extent after dropping all
+	 * the extents in the range. If this is true, the 'extent_item_size'
+	 * parameter must be set as well and the 'extent_inserted' field will
+	 * be set to true by btrfs_drop_extents() if it could insert the new
+	 * extent.
+	 * Note: when this is set to true the path must not be NULL.
+	 */
+	bool replace_extent;
+	/*
+	 * Used if 'replace_extent' is true. Size of the file extent item to
+	 * insert after dropping all existing extents in the range
+	 */
+	u32 extent_item_size;
+
+	/* Output parameters */
+
+	/*
+	 * Set to the minimum between the input parameter 'end' and the end
+	 * (exclusive, last byte + 1) of the last dropped extent. This is always
+	 * set even if btrfs_drop_extents() returns an error.
+	 */
+	u64 drop_end;
+	/*
+	 * Only set if 'replace_extent' is true. Set to true if we were able
+	 * to insert a replacement extent after dropping all extents in the
+	 * range, otherwise set to false by btrfs_drop_extents().
+	 * Also, if btrfs_drop_extents() has set this to true it means it
+	 * returned with the path locked, otherwise if it has set this to
+	 * false it has returned with the path released.
+	 */
+	bool extent_inserted;
+};
+
 struct btrfs_file_private {
 	void *filldir_buf;
 };
@@ -3119,16 +3171,9 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync);
 void btrfs_drop_extent_cache(struct btrfs_inode *inode, u64 start, u64 end,
 			     int skip_pinned);
 extern const struct file_operations btrfs_file_operations;
-int __btrfs_drop_extents(struct btrfs_trans_handle *trans,
-			 struct btrfs_root *root, struct btrfs_inode *inode,
-			 struct btrfs_path *path, u64 start, u64 end,
-			 u64 *drop_end, int drop_cache,
-			 int replace_extent,
-			 u32 extent_item_size,
-			 int *key_inserted);
 int btrfs_drop_extents(struct btrfs_trans_handle *trans,
-		       struct btrfs_root *root, struct inode *inode, u64 start,
-		       u64 end, int drop_cache);
+		       struct btrfs_root *root, struct btrfs_inode *inode,
+		       struct btrfs_drop_extents_args *args);
 int btrfs_replace_file_extents(struct inode *inode, struct btrfs_path *path,
 			   const u64 start, const u64 end,
 			   struct btrfs_replace_extent_info *extent_info,

fs/btrfs/inode.c

@@ -202,7 +202,7 @@ static int btrfs_init_inode_security(struct btrfs_trans_handle *trans,
  * no overlapping inline items exist in the btree
  */
 static int insert_inline_extent(struct btrfs_trans_handle *trans,
-				struct btrfs_path *path, int extent_inserted,
+				struct btrfs_path *path, bool extent_inserted,
 				struct btrfs_root *root, struct inode *inode,
 				u64 start, size_t size, size_t compressed_size,
 				int compress_type,
@@ -316,6 +316,7 @@ static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
 					  int compress_type,
 					  struct page **compressed_pages)
 {
+	struct btrfs_drop_extents_args drop_args = { 0 };
 	struct btrfs_root *root = inode->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_trans_handle *trans;
@@ -326,8 +327,6 @@ static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
 	u64 data_len = inline_len;
 	int ret;
 	struct btrfs_path *path;
-	int extent_inserted = 0;
-	u32 extent_item_size;
 
 	if (compressed_size)
 		data_len = compressed_size;
@@ -353,16 +352,20 @@ static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
 	}
 	trans->block_rsv = &inode->block_rsv;
 
+	drop_args.path = path;
+	drop_args.start = start;
+	drop_args.end = aligned_end;
+	drop_args.drop_cache = true;
+	drop_args.replace_extent = true;
+
 	if (compressed_size && compressed_pages)
-		extent_item_size = btrfs_file_extent_calc_inline_size(
+		drop_args.extent_item_size = btrfs_file_extent_calc_inline_size(
 		   compressed_size);
 	else
-		extent_item_size = btrfs_file_extent_calc_inline_size(
+		drop_args.extent_item_size = btrfs_file_extent_calc_inline_size(
 		    inline_len);
 
-	ret = __btrfs_drop_extents(trans, root, inode, path, start, aligned_end,
-				   NULL, 1, 1, extent_item_size,
-				   &extent_inserted);
+	ret = btrfs_drop_extents(trans, root, inode, &drop_args);
 	if (ret) {
 		btrfs_abort_transaction(trans, ret);
 		goto out;
@@ -370,7 +373,7 @@ static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
 
 	if (isize > actual_end)
 		inline_len = min_t(u64, isize, actual_end);
-	ret = insert_inline_extent(trans, path, extent_inserted,
+	ret = insert_inline_extent(trans, path, drop_args.extent_inserted,
 				   root, &inode->vfs_inode, start,
 				   inline_len, compressed_size,
 				   compress_type, compressed_pages);
@@ -2568,7 +2571,7 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 	u64 disk_bytenr = btrfs_stack_file_extent_disk_bytenr(stack_fi);
 	u64 num_bytes = btrfs_stack_file_extent_num_bytes(stack_fi);
 	u64 ram_bytes = btrfs_stack_file_extent_ram_bytes(stack_fi);
-	int extent_inserted = 0;
+	struct btrfs_drop_extents_args drop_args = { 0 };
 	int ret;
 
 	path = btrfs_alloc_path();
@@ -2584,13 +2587,16 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 	 * the caller is expected to unpin it and allow it to be merged
 	 * with the others.
 	 */
-	ret = __btrfs_drop_extents(trans, root, inode, path, file_pos,
-				   file_pos + num_bytes, NULL, 0,
-				   1, sizeof(*stack_fi), &extent_inserted);
+	drop_args.path = path;
+	drop_args.start = file_pos;
+	drop_args.end = file_pos + num_bytes;
+	drop_args.replace_extent = true;
+	drop_args.extent_item_size = sizeof(*stack_fi);
+	ret = btrfs_drop_extents(trans, root, inode, &drop_args);
 	if (ret)
 		goto out;
 
-	if (!extent_inserted) {
+	if (!drop_args.extent_inserted) {
 		ins.objectid = btrfs_ino(inode);
 		ins.offset = file_pos;
 		ins.type = BTRFS_EXTENT_DATA_KEY;
@@ -4748,6 +4754,7 @@ static int maybe_insert_hole(struct btrfs_root *root, struct inode *inode,
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_trans_handle *trans;
+	struct btrfs_drop_extents_args drop_args = { 0 };
 	int ret;
 
 	/*
@@ -4770,7 +4777,11 @@ static int maybe_insert_hole(struct btrfs_root *root, struct inode *inode,
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);
 
-	ret = btrfs_drop_extents(trans, root, inode, offset, offset + len, 1);
+	drop_args.start = offset;
+	drop_args.end = offset + len;
+	drop_args.drop_cache = true;
+
+	ret = btrfs_drop_extents(trans, root, BTRFS_I(inode), &drop_args);
 	if (ret) {
 		btrfs_abort_transaction(trans, ret);
 		btrfs_end_transaction(trans);

fs/btrfs/reflink.c

@@ -163,6 +163,7 @@ static int clone_copy_inline_extent(struct inode *dst,
 	const u64 aligned_end = ALIGN(new_key->offset + datal,
 				      fs_info->sectorsize);
 	struct btrfs_trans_handle *trans = NULL;
+	struct btrfs_drop_extents_args drop_args = { 0 };
 	int ret;
 	struct btrfs_key key;
 
@@ -252,7 +253,11 @@ static int clone_copy_inline_extent(struct inode *dst,
 		trans = NULL;
 		goto out;
 	}
-	ret = btrfs_drop_extents(trans, root, dst, drop_start, aligned_end, 1);
+	drop_args.path = path;
+	drop_args.start = drop_start;
+	drop_args.end = aligned_end;
+	drop_args.drop_cache = true;
+	ret = btrfs_drop_extents(trans, root, BTRFS_I(dst), &drop_args);
 	if (ret)
 		goto out;
 	ret = btrfs_insert_empty_item(trans, root, path, new_key, size);

fs/btrfs/tree-log.c

@@ -576,6 +576,7 @@ static noinline int replay_one_extent(struct btrfs_trans_handle *trans,
 				      struct extent_buffer *eb, int slot,
 				      struct btrfs_key *key)
 {
+	struct btrfs_drop_extents_args drop_args = { 0 };
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	int found_type;
 	u64 extent_end;
@@ -653,7 +654,10 @@ static noinline int replay_one_extent(struct btrfs_trans_handle *trans,
 	btrfs_release_path(path);
 
 	/* drop any overlapping extents */
-	ret = btrfs_drop_extents(trans, root, inode, start, extent_end, 1);
+	drop_args.start = start;
+	drop_args.end = extent_end;
+	drop_args.drop_cache = true;
+	ret = btrfs_drop_extents(trans, root, BTRFS_I(inode), &drop_args);
 	if (ret)
 		goto out;
 
@@ -2576,6 +2580,7 @@ static int replay_one_buffer(struct btrfs_root *log, struct extent_buffer *eb,
 			 * those prealloc extents just after replaying them.
 			 */
 			if (S_ISREG(mode)) {
+				struct btrfs_drop_extents_args drop_args = { 0 };
 				struct inode *inode;
 				u64 from;
 
@@ -2586,8 +2591,12 @@ static int replay_one_buffer(struct btrfs_root *log, struct extent_buffer *eb,
 				}
 				from = ALIGN(i_size_read(inode),
 					     root->fs_info->sectorsize);
-				ret = btrfs_drop_extents(wc->trans, root, inode,
-							 from, (u64)-1, 1);
+				drop_args.start = from;
+				drop_args.end = (u64)-1;
+				drop_args.drop_cache = true;
+				ret = btrfs_drop_extents(wc->trans, root,
+							 BTRFS_I(inode),
+							 &drop_args);
 				if (!ret) {
 					/* Update the inode's nbytes. */
 					ret = btrfs_update_inode(wc->trans,
@@ -4185,6 +4194,7 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
 			  struct btrfs_path *path,
 			  struct btrfs_log_ctx *ctx)
 {
+	struct btrfs_drop_extents_args drop_args = { 0 };
 	struct btrfs_root *log = root->log_root;
 	struct btrfs_file_extent_item *fi;
 	struct extent_buffer *leaf;
@@ -4193,19 +4203,21 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
 	u64 extent_offset = em->start - em->orig_start;
 	u64 block_len;
 	int ret;
-	int extent_inserted = 0;
 
 	ret = log_extent_csums(trans, inode, log, em, ctx);
 	if (ret)
 		return ret;
 
-	ret = __btrfs_drop_extents(trans, log, inode, path, em->start,
-				   em->start + em->len, NULL, 0, 1,
-				   sizeof(*fi), &extent_inserted);
+	drop_args.path = path;
+	drop_args.start = em->start;
+	drop_args.end = em->start + em->len;
+	drop_args.replace_extent = true;
+	drop_args.extent_item_size = sizeof(*fi);
+	ret = btrfs_drop_extents(trans, log, inode, &drop_args);
 	if (ret)
 		return ret;
 
-	if (!extent_inserted) {
+	if (!drop_args.extent_inserted) {
 		key.objectid = btrfs_ino(inode);
 		key.type = BTRFS_EXTENT_DATA_KEY;
 		key.offset = em->start;