linux-kernel - Re: [f2fs-dev] [PATCH 6/6] f2fs: set I_LINKABLE early to avoid wrong access by vfs

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Message-ID: <20191211013124.GB57416@jaegeuk-macbookpro.roam.corp.google.com>
Date:   Tue, 10 Dec 2019 17:31:24 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 6/6] f2fs: set I_LINKABLE early to avoid wrong
 access by vfs

On 12/11, Chao Yu wrote:
> On 2019/12/11 9:21, Jaegeuk Kim wrote:
> > On 12/10, Chao Yu wrote:
> >> On 2019/12/10 6:23, Jaegeuk Kim wrote:
> >>> This patch moves setting I_LINKABLE early in rename2(whiteout) to avoid the
> >>> below warning.
> >>>
> >>> [ 3189.163385] WARNING: CPU: 3 PID: 59523 at fs/inode.c:358 inc_nlink+0x32/0x40
> >>> [ 3189.246979] Call Trace:
> >>> [ 3189.248707]  f2fs_init_inode_metadata+0x2d6/0x440 [f2fs]
> >>> [ 3189.251399]  f2fs_add_inline_entry+0x162/0x8c0 [f2fs]
> >>> [ 3189.254010]  f2fs_add_dentry+0x69/0xe0 [f2fs]
> >>> [ 3189.256353]  f2fs_do_add_link+0xc5/0x100 [f2fs]
> >>> [ 3189.258774]  f2fs_rename2+0xabf/0x1010 [f2fs]
> >>> [ 3189.261079]  vfs_rename+0x3f8/0xaa0
> >>> [ 3189.263056]  ? tomoyo_path_rename+0x44/0x60
> >>> [ 3189.265283]  ? do_renameat2+0x49b/0x550
> >>> [ 3189.267324]  do_renameat2+0x49b/0x550
> >>> [ 3189.269316]  __x64_sys_renameat2+0x20/0x30
> >>> [ 3189.271441]  do_syscall_64+0x5a/0x230
> >>> [ 3189.273410]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >>> [ 3189.275848] RIP: 0033:0x7f270b4d9a49
> >>>
> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> >>> ---
> >>>  fs/f2fs/namei.c | 27 +++++++++++++--------------
> >>>  1 file changed, 13 insertions(+), 14 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> >>> index a1c507b0b4ac..5d9584281935 100644
> >>> --- a/fs/f2fs/namei.c
> >>> +++ b/fs/f2fs/namei.c
> >>> @@ -797,6 +797,7 @@ static int __f2fs_tmpfile(struct inode *dir, struct dentry *dentry,
> >>>  
> >>>  	if (whiteout) {
> >>>  		f2fs_i_links_write(inode, false);
> >>> +		inode->i_state |= I_LINKABLE;
> >>>  		*whiteout = inode;
> >>>  	} else {
> >>>  		d_tmpfile(dentry, inode);
> >>> @@ -867,6 +868,12 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
> >>>  			F2FS_I(old_dentry->d_inode)->i_projid)))
> >>>  		return -EXDEV;
> >>>  
> >>> +	if (flags & RENAME_WHITEOUT) {
> >>> +		err = f2fs_create_whiteout(old_dir, &whiteout);
> >>> +		if (err)
> >>> +			return err;
> >>> +	}
> >>
> >> To record quota info correctly, we need to create whiteout inode after
> >> dquot_initialize(old_dir)?
> > 
> > __f2fs_tmpfile() will do it.
> 
> Okay.
> 
> Any comments on below question?
> 
> > 
> >>
> >>> +
> >>>  	err = dquot_initialize(old_dir);
> >>>  	if (err)
> >>>  		goto out;
> >>> @@ -898,17 +905,11 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
> >>>  		}
> >>>  	}
> >>>  
> >>> -	if (flags & RENAME_WHITEOUT) {
> >>> -		err = f2fs_create_whiteout(old_dir, &whiteout);
> >>> -		if (err)
> >>> -			goto out_dir;
> >>> -	}
> >>> -
> >>>  	if (new_inode) {
> >>>  
> >>>  		err = -ENOTEMPTY;
> >>>  		if (old_dir_entry && !f2fs_empty_dir(new_inode))
> >>> -			goto out_whiteout;
> >>> +			goto out_dir;
> >>>  
> >>>  		err = -ENOENT;
> >>>  		new_entry = f2fs_find_entry(new_dir, &new_dentry->d_name,
> >>> @@ -916,7 +917,7 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
> >>>  		if (!new_entry) {
> >>>  			if (IS_ERR(new_page))
> >>>  				err = PTR_ERR(new_page);
> >>> -			goto out_whiteout;
> >>> +			goto out_dir;
> >>>  		}
> >>>  
> >>>  		f2fs_balance_fs(sbi, true);
> >>> @@ -948,7 +949,7 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
> >>>  		err = f2fs_add_link(new_dentry, old_inode);
> >>>  		if (err) {
> >>>  			f2fs_unlock_op(sbi);
> >>> -			goto out_whiteout;
> >>> +			goto out_dir;
> >>>  		}
> >>>  
> >>>  		if (old_dir_entry)
> >>> @@ -972,7 +973,7 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
> >>>  				if (IS_ERR(old_page))
> >>>  					err = PTR_ERR(old_page);
> >>>  				f2fs_unlock_op(sbi);
> >>> -				goto out_whiteout;
> >>> +				goto out_dir;
> >>>  			}
> >>>  		}
> >>>  	}
> >>> @@ -991,7 +992,6 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
> >>>  	f2fs_delete_entry(old_entry, old_page, old_dir, NULL);
> >>>  
> >>>  	if (whiteout) {
> >>> -		whiteout->i_state |= I_LINKABLE;
> >>>  		set_inode_flag(whiteout, FI_INC_LINK);
> >>>  		err = f2fs_add_link(old_dentry, whiteout);
> >>
> >> [ 3189.256353]  f2fs_do_add_link+0xc5/0x100 [f2fs]
> >> [ 3189.258774]  f2fs_rename2+0xabf/0x1010 [f2fs]
> >>
> >> Does the call stack point here? if so, we have set I_LINKABLE before
> >> f2fs_add_link(), why the warning still be triggered?
> 
> Am I missing something?

Not sure exactly tho, I suspect some races before/after unlock_new_inode().

> 
> Thanks,
> 
> >>
> >> Thanks,
> >>
> >>>  		if (err)
> >>> @@ -1027,15 +1027,14 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
> >>>  	f2fs_unlock_op(sbi);
> >>>  	if (new_page)
> >>>  		f2fs_put_page(new_page, 0);
> >>> -out_whiteout:
> >>> -	if (whiteout)
> >>> -		iput(whiteout);
> >>>  out_dir:
> >>>  	if (old_dir_entry)
> >>>  		f2fs_put_page(old_dir_page, 0);
> >>>  out_old:
> >>>  	f2fs_put_page(old_page, 0);
> >>>  out:
> >>> +	if (whiteout)
> >>> +		iput(whiteout);
> >>>  	return err;
> >>>  }
> >>>  
> >>>
> > .
> >