linux-kernel - [PATCH] fs/overlayfs: Drop dentry cache to prevent unknown file status

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Date:   Tue, 20 Mar 2018 14:03:50 +0800
From:   "王元良" <yuanliang.wyl@...baba-inc.com>
To:     miklos@...redi.hu
Cc:     <linux-unionfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "王元良" <yuanliang.wyl@...baba-inc.com>
Subject: [PATCH] fs/overlayfs: Drop dentry cache to prevent unknown file status

When the dentry cache is not destroyed, statfs will
take unknown status '?'
Undestroyed cache dentry also caused new file creating fails

Drop it using d_delete may be a choice

[root@...t /]
Loaded plugins: bestyumcache, branch, fastestmirror, langpacks
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache
fast
Cleaning repos: xxx.base.x86_64 ops.x.noarch ops.x.x86_64
Cleaning up everything
Cleaning up list of best yumcache
Cleaning up list of fastest mirrors

[root@...t /]
Loaded plugins: bestyumcache, branch, fastestmirror, langpacks
Cleaning repos: xxx.base.x86_64 ops.x.noarch ops.x.x86_64
Cleaning up everything
Cleaning up list of best yumcache
Traceback (most recent call last):
    File "/usr/bin/yum", line 29, in <module>
    yummain.user_main(sys.argv[1:], exit_code=True)
    File "/usr/share/yum-cli/yummain.py", line 365, in user_main
    errcode = main(args)
    File "/usr/share/yum-cli/yummain.py", line 174, in main
    result, resultmsgs = base.doCommands()
    File "/usr/share/yum-cli/cli.py", line 573, in doCommands
    return self.yum_cli_commands[self.basecmd].doCommand(self,
	    self.basecmd, self.extcmds)
	   File "/usr/share/yum-cli/yumcommands.py", line
    1475, in doCommand
    return base.cleanCli(extcmds)
    File "/usr/share/yum-cli/cli.py", line 1666, in
    cleanCli
    self.plugins.run('clean')
    File
    "/usr/lib/python2.7/site-packages/yum/plugins.py", line 188, in run
    func(conduitcls(self, self.base, conf, **kwargs))
    File "/usr/lib/yum-plugins/branch.py", line 65, in clean_hook
    os.remove(os.path.join(root,filespath))
    OSError: [Errno 2] No such file or directory:
	      '/var/cache/yum/x86_64/x/xxxx.noarch.stable/
	     b49e49b87d17818d799363091c7a01dde83b421d-primary.sqlite.bz2'

[root@...t /]
    ls: cannot access
    /var/cache/yum/x86_64/x/xxxx.noarch.stable/
    b49e49b87d17818d799363091c7a01dde83b421d-primary.sqlite.bz2:
    No such file or directory
    ls: cannot access
    /var/cache/yum/x86_64/x/xxxx.noarch.stable/cachecookie:
    No such file or directory
    ls: cannot access
    /var/cache/yum/x86_64/x/xxxx.noarch.stable/repomd.xml:
    No such file or directory
    total 0
    ?????????? ? ?    ?     ?            ?
    b49e49b87d17818d799363091c7a01dde83b421d-primary.sqlite.bz2
    ?????????? ? ?    ?     ?            ?
    cachecookie
    drwxr-xr-x 1 root root 30 Mar 15 16:12 gen
    drwxr-xr-x 2 root root  6 Jan 31 13:13
    packages
    ?????????? ? ?    ?     ?            ?
    repomd.xml

Signed-off-by: Yuanliang Wang <yuanliang.wyl@...baba-inc.com>
---
 fs/overlayfs/super.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index e7c8ac4..f9343d3 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -380,9 +380,15 @@ static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
 	return ret;
 }
 
+static int ovl_dentry_delete(const struct dentry *dentry)
+{
+	return 1;
+}
+
 static const struct dentry_operations ovl_dentry_operations = {
 	.d_release = ovl_dentry_release,
 	.d_real = ovl_d_real,
+	.d_delete = ovl_dentry_delete,
 };
 
 static const struct dentry_operations ovl_reval_dentry_operations = {
-- 
1.8.3.1