[PATCH] f2fs: compress: fix to cover f2fs_disable_compressed_file() w/ i_sem

[Chao Yu]

- f2fs_disable_compressed_file
  - check inode_has_data
					- f2fs_file_mmap
					- mkwrite
					 - f2fs_get_block_locked
					 : update metadata in compressed
					   inode's disk layout
  - fi->i_flags &= ~F2FS_COMPR_FL
  - clear_inode_flag(inode, FI_COMPRESSED_FILE);

we should use i_sem lock to prevent above race case.

Meanwhile, this patch adds i_size check to restrict compress inode
conversion condition.

Fixes: 4c8ff7095bef ("f2fs: support data compression")
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
 fs/f2fs/f2fs.h | 18 ++++++++++++++++--
 fs/f2fs/file.c |  5 ++---
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 74729db0b381..e2e0ca45f881 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4406,19 +4406,33 @@ static inline int set_compress_context(struct inode *inode)
 #endif
 }
 
+static inline bool inode_has_data(struct inode *inode)
+{
+	return (S_ISREG(inode->i_mode) &&
+		(F2FS_HAS_BLOCKS(inode) || i_size_read(inode)));
+}
+
 static inline bool f2fs_disable_compressed_file(struct inode *inode)
 {
 	struct f2fs_inode_info *fi = F2FS_I(inode);
 
-	if (!f2fs_compressed_file(inode))
+	f2fs_down_write(&F2FS_I(inode)->i_sem);
+
+	if (!f2fs_compressed_file(inode)) {
+		f2fs_up_write(&F2FS_I(inode)->i_sem);
 		return true;
-	if (S_ISREG(inode->i_mode) && F2FS_HAS_BLOCKS(inode))
+	}
+	if (f2fs_is_mmap_file(inode) || inode_has_data(inode)) {
+		f2fs_up_write(&F2FS_I(inode)->i_sem);
 		return false;
+	}
 
 	fi->i_flags &= ~F2FS_COMPR_FL;
 	stat_dec_compr_inode(inode);
 	clear_inode_flag(inode, FI_COMPRESSED_FILE);
 	f2fs_mark_inode_dirty_sync(inode, true);
+
+	f2fs_up_write(&F2FS_I(inode)->i_sem);
 	return true;
 }
 
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 0e4c871d6aed..5e5df234eb92 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1926,8 +1926,7 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
 
 			f2fs_down_write(&F2FS_I(inode)->i_sem);
 			if (!f2fs_may_compress(inode) ||
-					(S_ISREG(inode->i_mode) &&
-					F2FS_HAS_BLOCKS(inode))) {
+					inode_has_data(inode)) {
 				f2fs_up_write(&F2FS_I(inode)->i_sem);
 				return -EINVAL;
 			}
@@ -4011,7 +4010,7 @@ static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
 		goto out;
 	}
 
-	if (F2FS_HAS_BLOCKS(inode)) {
+	if (inode_has_data(inode)) {
 		ret = -EFBIG;
 		goto out;
 	}
-- 
2.40.1