btrfs: make can_nocow_extent nowait compatible

If we have NOWAIT specified on our IOCB and we're writing into a
PREALLOC or NOCOW extent then we need to be able to tell
can_nocow_extent that we don't want to wait on any locks or metadata IO.
Fix can_nocow_extent to allow for NOWAIT.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Stefan Roesch <shr@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3330,7 +3330,8 @@ int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
 				u64 offset, bool one_ordered);
 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
-			     struct list_head *list, int search_commit);
+			     struct list_head *list, int search_commit,
+			     bool nowait);
 void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
 				     const struct btrfs_path *path,
 				     struct btrfs_file_extent_item *fi,
@@ -3358,7 +3359,7 @@ int btrfs_check_data_csum(struct inode *inode, struct btrfs_bio *bbio,
 			  u32 bio_offset, struct page *page, u32 pgoff);
 noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
 			      u64 *orig_start, u64 *orig_block_len,
-			      u64 *ram_bytes, bool strict);
+			      u64 *ram_bytes, bool nowait, bool strict);
 
 void __btrfs_del_delalloc_inode(struct btrfs_root *root,
 				struct btrfs_inode *inode);

fs/btrfs/extent-tree.c

@@ -2220,6 +2220,12 @@ static noinline int check_delayed_ref(struct btrfs_root *root,
 	}
 
 	if (!mutex_trylock(&head->mutex)) {
+		if (path->nowait) {
+			spin_unlock(&delayed_refs->lock);
+			btrfs_put_transaction(cur_trans);
+			return -EAGAIN;
+		}
+
 		refcount_inc(&head->refs);
 		spin_unlock(&delayed_refs->lock);
 

fs/btrfs/file-item.c

@@ -511,7 +511,8 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u8 *dst
 }
 
 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
-			     struct list_head *list, int search_commit)
+			     struct list_head *list, int search_commit,
+			     bool nowait)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_key key;
@@ -533,6 +534,7 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 	if (!path)
 		return -ENOMEM;
 
+	path->nowait = nowait;
 	if (search_commit) {
 		path->skip_locking = 1;
 		path->reada = READA_FORWARD;

fs/btrfs/file.c

@@ -1501,7 +1501,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos,
 
 	btrfs_lock_and_flush_ordered_range(inode, lockstart, lockend, NULL);
 	ret = can_nocow_extent(&inode->vfs_inode, lockstart, &num_bytes,
-			NULL, NULL, NULL, false);
+			NULL, NULL, NULL, false, false);
 	if (ret <= 0) {
 		ret = 0;
 		btrfs_drew_write_unlock(&root->snapshot_lock);

fs/btrfs/inode.c

@@ -1666,7 +1666,7 @@ static noinline int run_delalloc_zoned(struct btrfs_inode *inode,
 }
 
 static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info,
-					u64 bytenr, u64 num_bytes)
+					u64 bytenr, u64 num_bytes, bool nowait)
 {
 	struct btrfs_root *csum_root = btrfs_csum_root(fs_info, bytenr);
 	struct btrfs_ordered_sum *sums;
@@ -1674,7 +1674,8 @@ static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info,
 	LIST_HEAD(list);
 
 	ret = btrfs_lookup_csums_range(csum_root, bytenr,
-				       bytenr + num_bytes - 1, &list, 0);
+				       bytenr + num_bytes - 1, &list, 0,
+				       nowait);
 	if (ret == 0 && list_empty(&list))
 		return 0;
 
@@ -1800,6 +1801,7 @@ static int can_nocow_file_extent(struct btrfs_path *path,
 	u8 extent_type;
 	int can_nocow = 0;
 	int ret = 0;
+	bool nowait = path->nowait;
 
 	fi = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_file_extent_item);
 	extent_type = btrfs_file_extent_type(leaf, fi);
@@ -1876,7 +1878,8 @@ static int can_nocow_file_extent(struct btrfs_path *path,
 	 * Force COW if csums exist in the range. This ensures that csums for a
 	 * given extent are either valid or do not exist.
 	 */
-	ret = csum_exist_in_range(root->fs_info, args->disk_bytenr, args->num_bytes);
+	ret = csum_exist_in_range(root->fs_info, args->disk_bytenr, args->num_bytes,
+				  nowait);
 	WARN_ON_ONCE(ret > 0 && is_freespace_inode);
 	if (ret != 0)
 		goto out;
@@ -7167,7 +7170,7 @@ static bool btrfs_extent_readonly(struct btrfs_fs_info *fs_info, u64 bytenr)
  */
 noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
 			      u64 *orig_start, u64 *orig_block_len,
-			      u64 *ram_bytes, bool strict)
+			      u64 *ram_bytes, bool nowait, bool strict)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct can_nocow_file_extent_args nocow_args = { 0 };
@@ -7183,6 +7186,7 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
+	path->nowait = nowait;
 
 	ret = btrfs_lookup_file_extent(NULL, root, path,
 			btrfs_ino(BTRFS_I(inode)), offset, 0);
@@ -7452,7 +7456,7 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
 		block_start = em->block_start + (start - em->start);
 
 		if (can_nocow_extent(inode, start, &len, &orig_start,
-				     &orig_block_len, &ram_bytes, false) == 1) {
+				     &orig_block_len, &ram_bytes, false, false) == 1) {
 			bg = btrfs_inc_nocow_writers(fs_info, block_start);
 			if (bg)
 				can_nocow = true;
@@ -11135,7 +11139,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
 		free_extent_map(em);
 		em = NULL;
 
-		ret = can_nocow_extent(inode, start, &len, NULL, NULL, NULL, true);
+		ret = can_nocow_extent(inode, start, &len, NULL, NULL, NULL, false, true);
 		if (ret < 0) {
 			goto out;
 		} else if (ret) {

fs/btrfs/relocation.c

@@ -4339,7 +4339,7 @@ int btrfs_reloc_clone_csums(struct btrfs_inode *inode, u64 file_pos, u64 len)
 	disk_bytenr = file_pos + inode->index_cnt;
 	csum_root = btrfs_csum_root(fs_info, disk_bytenr);
 	ret = btrfs_lookup_csums_range(csum_root, disk_bytenr,
-				       disk_bytenr + len - 1, &list, 0);
+				       disk_bytenr + len - 1, &list, 0, false);
 	if (ret)
 		goto out;
 

fs/btrfs/scrub.c

@@ -3229,7 +3229,7 @@ static int scrub_raid56_data_stripe_for_parity(struct scrub_ctx *sctx,
 
 		ret = btrfs_lookup_csums_range(csum_root, extent_start,
 					       extent_start + extent_size - 1,
-					       &sctx->csum_list, 1);
+					       &sctx->csum_list, 1, false);
 		if (ret) {
 			scrub_parity_mark_sectors_error(sparity, extent_start,
 							extent_size);
@@ -3455,7 +3455,7 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
 		if (extent_flags & BTRFS_EXTENT_FLAG_DATA) {
 			ret = btrfs_lookup_csums_range(csum_root, cur_logical,
 					cur_logical + scrub_len - 1,
-					&sctx->csum_list, 1);
+					&sctx->csum_list, 1, false);
 			if (ret)
 				break;
 		}

fs/btrfs/tree-log.c

@@ -801,7 +801,7 @@ static noinline int replay_one_extent(struct btrfs_trans_handle *trans,
 
 			ret = btrfs_lookup_csums_range(root->log_root,
 						csum_start, csum_end - 1,
-						&ordered_sums, 0);
+						&ordered_sums, 0, false);
 			if (ret)
 				goto out;
 			/*
@@ -4402,7 +4402,7 @@ static noinline int copy_items(struct btrfs_trans_handle *trans,
 		disk_bytenr += extent_offset;
 		ret = btrfs_lookup_csums_range(csum_root, disk_bytenr,
 					       disk_bytenr + extent_num_bytes - 1,
-					       &ordered_sums, 0);
+					       &ordered_sums, 0, false);
 		if (ret)
 			goto out;
 
@@ -4598,7 +4598,7 @@ static int log_extent_csums(struct btrfs_trans_handle *trans,
 	ret = btrfs_lookup_csums_range(csum_root,
 				       em->block_start + csum_offset,
 				       em->block_start + csum_offset +
-				       csum_len - 1, &ordered_sums, 0);
+				       csum_len - 1, &ordered_sums, 0, false);
 	if (ret)
 		return ret;