f2fs: compress: fix inconsistent update of i_blocks in release_compress_blocks and reserve_compress_blocks

After release a file and subsequently reserve it, the FSCK flag is set
when the file is deleted, as shown in the following backtrace:

F2FS-fs (dm-48): Inconsistent i_blocks, ino:401231, iblocks:1448, sectors:1472
fs_rec_info_write_type+0x58/0x274
f2fs_rec_info_write+0x1c/0x2c
set_sbi_flag+0x74/0x98
dec_valid_block_count+0x150/0x190
f2fs_truncate_data_blocks_range+0x2d4/0x3cc
f2fs_do_truncate_blocks+0x2fc/0x5f0
f2fs_truncate_blocks+0x68/0x100
f2fs_truncate+0x80/0x128
f2fs_evict_inode+0x1a4/0x794
evict+0xd4/0x280
iput+0x238/0x284
do_unlinkat+0x1ac/0x298
__arm64_sys_unlinkat+0x48/0x68
invoke_syscall+0x58/0x11c

For clusters of the following type, i_blocks are decremented by 1 and
i_compr_blocks are incremented by 7 in release_compress_blocks, while
updates to i_blocks and i_compr_blocks are skipped in reserve_compress_blocks.

raw node:
D D D D D D D D
after compress:
C D D D D D D D
after reserve:
C D D D D D D D

Let's update i_blocks and i_compr_blocks properly in reserve_compress_blocks.

Fixes: eb8fbaa ("f2fs: compress: fix to check unreleased compressed cluster")
Signed-off-by: Qi Han <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

Author: Qi Han

fs/f2fs/file.c

@@ -3792,7 +3792,7 @@ static int reserve_compress_blocks(struct dnode_of_data *dn, pgoff_t count,
 		to_reserved = cluster_size - compr_blocks - reserved;
 
 		/* for the case all blocks in cluster were reserved */
-		if (to_reserved == 1) {
+		if (reserved && to_reserved == 1) {
 			dn->ofs_in_node += cluster_size;
 			goto next;
 		}