f2fs: fix multiple f2fs_add_link() calls having same name
It turns out a stakable filesystem like sdcardfs in AOSP can trigger multiple
vfs_create() to lower filesystem. In that case, f2fs will add multiple dentries
having same name which breaks filesystem consistency.
Until upper layer fixes, let's work around by f2fs, which shows actually not
much performance regression.
Cc: <stable@vger.kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 827c5da..54aa30e 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -207,9 +207,13 @@
f2fs_put_page(dentry_page, 0);
}
- if (!de && room && F2FS_I(dir)->chash != namehash) {
- F2FS_I(dir)->chash = namehash;
- F2FS_I(dir)->clevel = level;
+ /* This is to increase the speed of f2fs_create */
+ if (!de && room) {
+ F2FS_I(dir)->task = current;
+ if (F2FS_I(dir)->chash != namehash) {
+ F2FS_I(dir)->chash = namehash;
+ F2FS_I(dir)->clevel = level;
+ }
}
return de;
@@ -643,14 +647,34 @@
struct inode *inode, nid_t ino, umode_t mode)
{
struct fscrypt_name fname;
+ struct page *page = NULL;
+ struct f2fs_dir_entry *de = NULL;
int err;
err = fscrypt_setup_filename(dir, name, 0, &fname);
if (err)
return err;
- err = __f2fs_do_add_link(dir, &fname, inode, ino, mode);
-
+ /*
+ * An immature stakable filesystem shows a race condition between lookup
+ * and create. If we have same task when doing lookup and create, it's
+ * definitely fine as expected by VFS normally. Otherwise, let's just
+ * verify on-disk dentry one more time, which guarantees filesystem
+ * consistency more.
+ */
+ if (current != F2FS_I(dir)->task) {
+ de = __f2fs_find_entry(dir, &fname, &page);
+ F2FS_I(dir)->task = NULL;
+ }
+ if (de) {
+ f2fs_dentry_kunmap(dir, page);
+ f2fs_put_page(page, 0);
+ err = -EEXIST;
+ } else if (IS_ERR(page)) {
+ err = PTR_ERR(page);
+ } else {
+ err = __f2fs_do_add_link(dir, &fname, inode, ino, mode);
+ }
fscrypt_free_filename(&fname);
return err;
}
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 28e9540..7b5e287 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -459,6 +459,7 @@
atomic_t dirty_pages; /* # of dirty pages */
f2fs_hash_t chash; /* hash value of given file name */
unsigned int clevel; /* maximum level of given file name */
+ struct task_struct *task; /* lookup and create consistency */
nid_t i_xattr_nid; /* node id that contains xattrs */
loff_t last_disk_size; /* lastly written file size */