[PATCH v2] fat: roll back the new entry when create/mkdir fails to build the inode

[zhoumin]

vfat_create(), vfat_mkdir(), msdos_create() and msdos_mkdir() add the
on-disk entry before calling fat_build_inode() to set up the VFS
inode.  If fat_build_inode() fails, the error is returned but the
entry stays on disk and the file or directory shows up after remount.

Remove the entry in that case.  For mkdir, also free the directory
cluster and decrement the parent's link count.

Signed-off-by: zhoumin <teczm@xxxxxxxxxxx>
---
Changes since v1:
 - Only undo the parent nlink and free the cluster when
   fat_remove_entries() succeeds.
 - Use a block scoped err2.
 - Reuse out_free instead of an open coded fat_free_clusters().

 fs/fat/namei_msdos.c | 22 ++++++++++++++++++----
 fs/fat/namei_vfat.c  | 22 ++++++++++++++++++----
 2 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index d46d1a3851f2..7f2c68149efd 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -292,11 +292,17 @@ static int msdos_create(struct mnt_idmap *idmap, struct inode *dir,
 	if (err)
 		goto out;
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
+		int err2;
+
 		err = PTR_ERR(inode);
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2)
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
 		goto out;
 	}
+	brelse(sinfo.bh);
 	fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
@@ -381,12 +387,20 @@ static struct dentry *msdos_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	inc_nlink(dir);
 
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
+		int err2;
+
 		err = PTR_ERR(inode);
-		/* the directory was completed, just return a error */
-		goto out;
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2) {
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
+			goto out;
+		}
+		drop_nlink(dir);
+		goto out_free;
 	}
+	brelse(sinfo.bh);
 	set_nlink(inode, 2);
 	fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index da3e89c0b16a..b366e0163272 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -771,11 +771,17 @@ static int vfat_create(struct mnt_idmap *idmap, struct inode *dir,
 	inode_inc_iversion(dir);
 
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
+		int err2;
+
 		err = PTR_ERR(inode);
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2)
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
 		goto out;
 	}
+	brelse(sinfo.bh);
 	inode_inc_iversion(inode);
 
 	d_instantiate(dentry, inode);
@@ -870,12 +876,20 @@ static struct dentry *vfat_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	inc_nlink(dir);
 
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
+		int err2;
+
 		err = PTR_ERR(inode);
-		/* the directory was completed, just return a error */
-		goto out;
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2) {
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
+			goto out;
+		}
+		drop_nlink(dir);
+		goto out_free;
 	}
+	brelse(sinfo.bh);
 	inode_inc_iversion(inode);
 	set_nlink(inode, 2);
 
-- 
2.53.0