btrfs: add the ability to use NO_FLUSH for data reservations

In order to accommodate NOWAIT IOCB's we need to be able to do NO_FLUSH
data reservations, so plumb this through the delalloc reservation
system.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Stefan Roesch <shr@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/block-group.c

@@ -2850,7 +2850,7 @@ static int cache_save_setup(struct btrfs_block_group *block_group,
 	cache_size *= fs_info->sectorsize;
 
 	ret = btrfs_check_data_free_space(BTRFS_I(inode), &data_reserved, 0,
-					  cache_size);
+					  cache_size, false);
 	if (ret)
 		goto out_put;
 

fs/btrfs/delalloc-space.c

@@ -127,9 +127,11 @@ int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes)
 }
 
 int btrfs_check_data_free_space(struct btrfs_inode *inode,
-			struct extent_changeset **reserved, u64 start, u64 len)
+				struct extent_changeset **reserved, u64 start,
+				u64 len, bool noflush)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
+	enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_FLUSH_DATA;
 	int ret;
 
 	/* align the range */
@@ -137,7 +139,12 @@ int btrfs_check_data_free_space(struct btrfs_inode *inode,
 	      round_down(start, fs_info->sectorsize);
 	start = round_down(start, fs_info->sectorsize);
 
-	ret = btrfs_alloc_data_chunk_ondemand(inode, len);
+	if (noflush)
+		flush = BTRFS_RESERVE_NO_FLUSH;
+	else if (btrfs_is_free_space_inode(inode))
+		flush = BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE;
+
+	ret = btrfs_reserve_data_bytes(fs_info, len, flush);
 	if (ret < 0)
 		return ret;
 
@@ -454,7 +461,7 @@ int btrfs_delalloc_reserve_space(struct btrfs_inode *inode,
 {
 	int ret;
 
-	ret = btrfs_check_data_free_space(inode, reserved, start, len);
+	ret = btrfs_check_data_free_space(inode, reserved, start, len, false);
 	if (ret < 0)
 		return ret;
 	ret = btrfs_delalloc_reserve_metadata(inode, len, len, false);

fs/btrfs/delalloc-space.h

@@ -7,7 +7,8 @@ struct extent_changeset;
 
 int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes);
 int btrfs_check_data_free_space(struct btrfs_inode *inode,
-			struct extent_changeset **reserved, u64 start, u64 len);
+			struct extent_changeset **reserved, u64 start, u64 len,
+			bool noflush);
 void btrfs_free_reserved_data_space(struct btrfs_inode *inode,
 			struct extent_changeset *reserved, u64 start, u64 len);
 void btrfs_delalloc_release_space(struct btrfs_inode *inode,

fs/btrfs/file.c

@@ -1663,7 +1663,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
 		extent_changeset_release(data_reserved);
 		ret = btrfs_check_data_free_space(BTRFS_I(inode),
 						  &data_reserved, pos,
-						  write_bytes);
+						  write_bytes, false);
 		if (ret < 0) {
 			/*
 			 * If we don't have to COW at the offset, reserve

fs/btrfs/inode.c

@@ -4885,7 +4885,7 @@ int btrfs_truncate_block(struct btrfs_inode *inode, loff_t from, loff_t len,
 	block_end = block_start + blocksize - 1;
 
 	ret = btrfs_check_data_free_space(inode, &data_reserved, block_start,
-					  blocksize);
+					  blocksize, false);
 	if (ret < 0) {
 		if (btrfs_check_nocow_lock(inode, block_start, &write_bytes) > 0) {
 			/* For nocow case, no need to reserve data space */
@@ -7641,7 +7641,7 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
 	if (write && !(flags & IOMAP_NOWAIT)) {
 		ret = btrfs_check_data_free_space(BTRFS_I(inode),
 						  &dio_data->data_reserved,
-						  start, data_alloc_len);
+						  start, data_alloc_len, false);
 		if (!ret)
 			dio_data->data_space_reserved = true;
 		else if (ret && !(BTRFS_I(inode)->flags &

fs/btrfs/space-info.c

@@ -1760,7 +1760,8 @@ int btrfs_reserve_data_bytes(struct btrfs_fs_info *fs_info, u64 bytes,
 	int ret;
 
 	ASSERT(flush == BTRFS_RESERVE_FLUSH_DATA ||
-	       flush == BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE);
+	       flush == BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE ||
+	       flush == BTRFS_RESERVE_NO_FLUSH);
 	ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA);
 
 	ret = __reserve_bytes(fs_info, data_sinfo, bytes, flush);