f2fs: compress: don't redirty sparse cluster during {,de}compress

In f2fs_do_write_data_page, when the data block is NULL_ADDR, it skips
writepage considering that it has been already truncated.
This results in an infinite loop as the PAGECACHE_TAG_TOWRITE tag is not
cleared during the writeback process for a compressed file including
NULL_ADDR in compress_mode=user.

This is the reproduction process:

1. dd if=/dev/zero bs=4096 count=1024 seek=1024 of=testfile
2. f2fs_io compress testfile
3. dd if=/dev/zero bs=4096 count=1 conv=notrunc of=testfile
4. f2fs_io decompress testfile

To prevent the problem, let's check whether the cluster is fully
allocated before redirty its pages.

Fixes: 5fdb322ff2c2 ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE")
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Sunmin Jeong <s_min.jeong@samsung.com>
Tested-by: Jaewook Kim <jw5454.kim@samsung.com>
Signed-off-by: Yeongjin Gil <youngjin.gil@samsung.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 21 insertions, 18 deletions

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 50075f8d5e9b..0bfcc1bf5832 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4236,9 +4236,8 @@ static int f2fs_ioc_decompress_file(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct f2fs_inode_info *fi = F2FS_I(inode);
-	pgoff_t page_idx = 0, last_idx;
-	int cluster_size = fi->i_cluster_size;
-	int count, ret;
+	pgoff_t page_idx = 0, last_idx, cluster_idx;
+	int ret;
 
 	if (!f2fs_sb_has_compression(sbi) ||
 			F2FS_OPTION(sbi).compress_mode != COMPR_MODE_USER)
@@ -4273,10 +4272,15 @@ static int f2fs_ioc_decompress_file(struct file *filp)
 		goto out;
 
 	last_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+	last_idx >>= fi->i_log_cluster_size;
+
+	for (cluster_idx = 0; cluster_idx < last_idx; cluster_idx++) {
+		page_idx = cluster_idx << fi->i_log_cluster_size;
+
+		if (!f2fs_is_compressed_cluster(inode, page_idx))
+			continue;
 
-	count = last_idx - page_idx;
-	while (count && count >= cluster_size) {
-		ret = redirty_blocks(inode, page_idx, cluster_size);
+		ret = redirty_blocks(inode, page_idx, fi->i_cluster_size);
 		if (ret < 0)
 			break;
 
@@ -4286,9 +4290,6 @@ static int f2fs_ioc_decompress_file(struct file *filp)
 				break;
 		}
 
-		count -= cluster_size;
-		page_idx += cluster_size;
-
 		cond_resched();
 		if (fatal_signal_pending(current)) {
 			ret = -EINTR;
@@ -4315,9 +4316,9 @@ static int f2fs_ioc_compress_file(struct file *filp)
 {
 	struct inode *inode = file_inode(filp);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
-	pgoff_t page_idx = 0, last_idx;
-	int cluster_size = F2FS_I(inode)->i_cluster_size;
-	int count, ret;
+	struct f2fs_inode_info *fi = F2FS_I(inode);
+	pgoff_t page_idx = 0, last_idx, cluster_idx;
+	int ret;
 
 	if (!f2fs_sb_has_compression(sbi) ||
 			F2FS_OPTION(sbi).compress_mode != COMPR_MODE_USER)
@@ -4351,10 +4352,15 @@ static int f2fs_ioc_compress_file(struct file *filp)
 	set_inode_flag(inode, FI_ENABLE_COMPRESS);
 
 	last_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+	last_idx >>= fi->i_log_cluster_size;
 
-	count = last_idx - page_idx;
-	while (count && count >= cluster_size) {
-		ret = redirty_blocks(inode, page_idx, cluster_size);
+	for (cluster_idx = 0; cluster_idx < last_idx; cluster_idx++) {
+		page_idx = cluster_idx << fi->i_log_cluster_size;
+
+		if (f2fs_is_sparse_cluster(inode, page_idx))
+			continue;
+
+		ret = redirty_blocks(inode, page_idx, fi->i_cluster_size);
 		if (ret < 0)
 			break;
 
@@ -4364,9 +4370,6 @@ static int f2fs_ioc_compress_file(struct file *filp)
 				break;
 		}
 
-		count -= cluster_size;
-		page_idx += cluster_size;
-
 		cond_resched();
 		if (fatal_signal_pending(current)) {
 			ret = -EINTR;