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

Jaegeuk Kim
2020-05-05T18:13:26Z

On 05/05, Eric Biggers wrote:
> On Tue, May 05, 2020 at 08:31:39AM -0700, Jaegeuk Kim wrote:
> > We had to grab the inode before retrieving i_ino.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> > fs/f2fs/file.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index a0a4413d6083b..9d4c3e3503567 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -168,6 +168,7 @@ static const struct vm_operations_struct f2fs_file_vm_ops = {
> > static int get_parent_ino(struct inode *inode, nid_t *pino)
> > {
> > struct dentry *dentry;
> > + struct inode *parent;
> >
> > inode = igrab(inode);
> > dentry = d_find_any_alias(inode);
> > @@ -175,8 +176,13 @@ static int get_parent_ino(struct inode *inode, nid_t *pino)
> > if (!dentry)
> > return 0;
> >
> > - *pino = parent_ino(dentry);
> > + parent = igrab(d_inode(dentry->d_parent));
> > dput(dentry);
> > + if (!parent)
> > + return 0;
> > +
> > + *pino = parent->i_ino;
> > + iput(parent);
> > return 1;

Hi Eric,

>
> This doesn't appear to be necessary. parent_ino() is:
>
> spin_lock(&dentry->d_lock);
> res = dentry->d_parent->d_inode->i_ino;
> spin_unlock(&dentry->d_lock);
>
> Since dentry is locked and referenced, ->d_parent is stable and positive.

I see, thanks. :)

>
> In the encrypt+casefold patch I was reviewing, it's indeed necessary, but only
> because there was a check of inode->i_flags added outside the locked region.
> The following would be simpler:
>
> spin_lock(&dentry->d_lock);
> dir = dentry->d_parent->d_inode;
> *pino = dir->i_ino;
> needs_recovery = IS_ENCRYPTED(dir) && IS_CASEFOLDED(dir);
> spin_unlock(&dentry->d_lock);

Ack.

>
> BTW, d_find_any_alias() is unnecessary too. This code should just be using
> file_dentry(file) from f2fs_do_sync_file().

How about this?

From 9aee969a413b1ed22b48573071bc93fbb4a2002d Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Tue, 5 May 2020 11:08:58 -0700
Subject: [PATCH] f2fs: remove unnecessary dentry locks

As Eric commented, let's kill unnecessary dentry ops when recovering
parent inode number.

Suggested-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
fs/f2fs/file.c | 26 ++++++--------------------
1 file changed, 6 insertions(+), 20 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index a0a4413d6083b..711cebad36fc5 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -165,21 +165,6 @@ static const struct vm_operations_struct f2fs_file_vm_ops = {
.page_mkwrite = f2fs_vm_page_mkwrite,
};

-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);
- if (!dentry)
- return 0;
-
- *pino = parent_ino(dentry);
- dput(dentry);
- return 1;
-}
-
static inline enum cp_reason_type need_do_checkpoint(struct inode *inode)
{
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
@@ -223,14 +208,15 @@ static bool need_inode_page_update(struct f2fs_sb_info *sbi, nid_t ino)
return ret;
}

-static void try_to_fix_pino(struct inode *inode)
+static void try_to_fix_pino(struct dentry *dentry)
{
+ struct inode *inode = d_inode(dentry);
struct f2fs_inode_info *fi = F2FS_I(inode);
- nid_t pino;

down_write(&fi->i_sem);
- if (file_wrong_pino(inode) && inode->i_nlink == 1 &&
- get_parent_ino(inode, &pino)) {
+ if (file_wrong_pino(inode) && inode->i_nlink == 1) {
+ nid_t pino = parent_ino(dentry);
+
f2fs_i_pino_write(inode, pino);
file_got_pino(inode);
}
@@ -310,7 +296,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
* We've secured consistency through sync_fs. Following pino
* will be used only for fsynced inodes after checkpoint.
*/
- try_to_fix_pino(inode);
+ try_to_fix_pino(file_dentry(file));
clear_inode_flag(inode, FI_APPEND_WRITE);
clear_inode_flag(inode, FI_UPDATE_WRITE);
goto out;
--
2.26.2.526.g744177e7f7-goog