[f2fs-dev] [PATCH v2 1/2] f2fs: don't allow unaligned truncation to smaller size on pinned file

[wangzijie]

To prevent scattered pin block generation, don't allow non-section aligned truncation
to smaller size on pinned file. But for truncation to larger size, after
commit 3fdd89b452c2("f2fs: prevent writing without fallocate() for pinned files"),
we only support overwrite IO to pinned file, so we don't need to consider
attr->ia_size > i_size case.

Signed-off-by: wangzijie <wangzijie1@xxxxxxxxx>
---
v2:
- add comments and change a proper subject
---
 fs/f2fs/file.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 6bd3de64f..09be6e849 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1026,6 +1026,7 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 {
 	struct inode *inode = d_inode(dentry);
 	struct f2fs_inode_info *fi = F2FS_I(inode);
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	int err;
 
 	if (unlikely(f2fs_cp_error(F2FS_I_SB(inode))))
@@ -1047,6 +1048,17 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 			!IS_ALIGNED(attr->ia_size,
 			F2FS_BLK_TO_BYTES(fi->i_cluster_size)))
 			return -EINVAL;
+		/*
+		 * To prevent scattered pin block generation, we don't
+		 * allow smaller size unaligned truncation for pinned file.
+		 * We only support overwrite IO to pinned file, so don't
+		 * care about larger size truncation.
+		 */
+		if (f2fs_is_pinned_file(inode) &&
+			attr->ia_size < i_size_read(inode) &&
+			!IS_ALIGNED(attr->ia_size,
+			F2FS_BLK_TO_BYTES(CAP_BLKS_PER_SEC(sbi))))
+			return -EINVAL;
 	}
 
 	err = setattr_prepare(idmap, dentry, attr);
-- 
2.25.1