From: Amir Goldstein <amir73il@gmail.com>
To: Chengguang Xu <cgxu519@mykernel.net>
Cc: Jan Kara <jack@suse.cz>, miklos <miklos@szeredi.hu>,
linux-unionfs <linux-unionfs@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [RFC PATCH 1/5] fs: introduce notifier list for vfs inode
Date: Thu, 15 Oct 2020 19:06:44 +0300 [thread overview]
Message-ID: <CAOQ4uxhyh4i_0sEtkDkAsEARRU_J2Df1xKRSVZP9st8QPTPnww@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxhujP_pzguq+FJ87Mx4GBNzEWQs-izuXK1qhWu3EmLpJA@mail.gmail.com>
> Very well, I will try to explain with code:
>
> int ovl_inode_is_open_for_write(struct inode *inode)
> {
> struct inode *upper_inode = ovl_inode_upper(inode);
>
> return upper_inode && inode_is_open_for_write(upper_inode);
> }
>
> void ovl_maybe_mark_inode_dirty(struct inode *inode)
> {
> struct inode *upper_inode = ovl_inode_upper(inode);
>
> if (upper_inode && upper_inode->i_state & I_DIRTY_ALL)
> mark_inode_dirty(inode);
> }
>
> int ovl_open(struct inode *inode, struct file *file)
> {
> ...
> if (ovl_inode_is_open_for_write(file_inode(file)))
> ovl_add_inode_to_suspect_list(inode);
>
> file->private_data = realfile;
>
> return 0;
> }
>
> int ovl_release(struct inode *inode, struct file *file)
> {
> struct inode *inode = file_inode(file);
>
> if (ovl_inode_is_open_for_write(inode)) {
Darn! that should have been (!ovl_inode_is_open_for_write(inode))
and it should be done after fput() and grabbing inode reference with
ihold() before fput().
> ovl_maybe_mark_inode_dirty(inode);
> ovl_remove_inode_from_suspect_list(inode);
> }
>
> fput(file->private_data);
>
> return 0;
> }
>
> int ovl_drop_inode(struct inode *inode)
> {
> struct inode *upper_inode = ovl_inode_upper(inode);
>
> if (!upper_inode)
> return 1;
> if (upper_inode->i_state & I_DIRTY_ALL)
> return 0;
>
> return !inode_is_open_for_write(upper_inode);
> }
>
> static int ovl_sync_fs(struct super_block *sb, int wait)
> {
> struct ovl_fs *ofs = sb->s_fs_info;
> struct super_block *upper_sb;
> int ret;
>
> if (!ovl_upper_mnt(ofs))
> return 0;
>
> /*
> * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
> * All the super blocks will be iterated, including upper_sb.
> *
> * If this is a syncfs(2) call, then we do need to call
> * sync_filesystem() on upper_sb, but enough if we do it when being
> * called with wait == 1.
> */
> if (!wait) {
> /* mark inodes on the suspect list dirty if thier
> upper inode is dirty */
> ovl_mark_suspect_list_inodes_dirty();
> return 0;
> }
> ...
>
>
> The races are avoided because inode is added/removed from suspect
> list while overlay inode has a reference (from file) and because upper inode
> cannot be dirtied by overlayfs when overlay inode is not on the suspect list.
>
> Unless I am missing something.
>
> Thanks,
> Amir.
next prev parent reply other threads:[~2020-10-15 16:06 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-10 14:23 [RFC PATCH 0/5] implement containerized syncfs for overlayfs Chengguang Xu
2020-10-10 14:23 ` [RFC PATCH 1/5] fs: introduce notifier list for vfs inode Chengguang Xu
2020-10-14 16:15 ` Jan Kara
2020-10-15 3:03 ` Chengguang Xu
2020-10-15 6:11 ` Amir Goldstein
2020-10-15 11:29 ` Chengguang Xu
2020-10-15 12:32 ` Amir Goldstein
2020-10-15 13:13 ` Chengguang Xu
2020-10-15 16:02 ` Amir Goldstein
2020-10-15 16:06 ` Amir Goldstein [this message]
2020-10-16 1:56 ` Chengguang Xu
2020-10-16 4:39 ` Amir Goldstein
2020-10-16 7:43 ` Chengguang Xu
2020-10-15 3:25 ` Al Viro
2020-10-15 3:42 ` Chengguang Xu
2020-10-15 4:57 ` Al Viro
2020-10-15 10:56 ` Chengguang Xu
2020-10-16 7:09 ` Chengguang Xu
2020-10-16 9:22 ` Jan Kara
2020-10-10 14:23 ` [RFC PATCH 2/5] fs: export symbol of writeback_single_inode() Chengguang Xu
2020-10-10 14:23 ` [RFC PATCH 3/5] ovl: setup overlayfs' private bdi Chengguang Xu
2020-10-10 14:23 ` [RFC PATCH 4/5] ovl: monitor marking dirty activity of underlying upper inode Chengguang Xu
2020-10-10 14:23 ` [RFC PATCH 5/5] ovl: impement containerized syncfs for overlayfs Chengguang Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAOQ4uxhyh4i_0sEtkDkAsEARRU_J2Df1xKRSVZP9st8QPTPnww@mail.gmail.com \
--to=amir73il@gmail.com \
--cc=cgxu519@mykernel.net \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-unionfs@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).