Re: [f2fs-dev] [PATCH] f2fs: get parent inode when recovering pino

Eric Biggers
2020-05-05T19:01:11Z

On Tue, May 05, 2020 at 11:49:32AM -0700, Jaegeuk Kim wrote:
> How about this?
>
> From 2a6b0e53e592854306062a2dc35db2d8f79062f2 Mon Sep 17 00:00:00 2001
> From: Jaegeuk Kim <jaegeuk@kernel.org>
> Date: Tue, 5 May 2020 11:33:29 -0700
> Subject: [PATCH] f2fs: find a living dentry when finding parent ino
>
> We need to check any dentry still alive to get parent inode number.
>
> Suggested-by: Eric Biggers <ebiggers@kernel.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
> fs/f2fs/file.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index a0a4413d6083b..95139cb85faca 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -169,9 +169,8 @@ static int get_parent_ino(struct inode *inode, nid_t *pino)
> {
> struct dentry *dentry;
>
> - inode = igrab(inode);
> - dentry = d_find_any_alias(inode);
> - iput(inode);
> + /* Need to check if valid dentry still exists. */
> + dentry = d_find_alias(inode);
> if (!dentry)
> return 0;
>

It's fine, but it could use some more explanation. (What's a "valid dentry"?)
How about the following?

From f8fe7d57eead1423e8548ac7a5ec881d701466a5 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Tue, 5 May 2020 11:41:11 -0700
Subject: [PATCH] f2fs: correctly fix the parent inode number during fsync()

fsync() may be called on a deleted file that's still open. So when
fsync() tries to set the parent inode number when the inode has
LOST_PINO and i_nlink == 1 (to avoid later checkpoints), it needs to
make sure to get the parent directory via a non-deleted alias.

Also remove the unnecessary igrab() and iput(), as the caller already
holds a reference to the inode.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/f2fs/file.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 6ab8f621a3c5a2..b3069188fd3478 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -165,9 +165,11 @@ static int get_parent_ino(struct inode *inode, nid_t *pino)
{
struct dentry *dentry;

- inode = igrab(inode);
- dentry = d_find_any_alias(inode);
- iput(inode);
+ /*
+ * Make sure to get the non-deleted alias. The alias associated with
+ * the open file descriptor being fsync()'ed may be deleted already.
+ */
+ dentry = d_find_alias(inode);
if (!dentry)
return 0;

--
2.26.2