From: Jan Kara <jack@suse.cz>
To: Chengguang Xu <cgxu519@mykernel.net>
Cc: miklos@szeredi.hu, amir73il@gmail.com, jack@suse.cz,
linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [RFC PATCH v2 2/8] ovl: implement ->writepages operation
Date: Mon, 2 Nov 2020 18:17:41 +0100 [thread overview]
Message-ID: <20201102171741.GE23988@quack2.suse.cz> (raw)
In-Reply-To: <20201025034117.4918-3-cgxu519@mykernel.net>
On Sun 25-10-20 11:41:11, Chengguang Xu wrote:
> Implement overlayfs' ->writepages operation so that
> we can sync dirty data/metadata to upper filesystem.
>
> Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
> ---
> fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index b584dca845ba..f27fc5be34df 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -11,6 +11,7 @@
> #include <linux/posix_acl.h>
> #include <linux/ratelimit.h>
> #include <linux/fiemap.h>
> +#include <linux/writeback.h>
> #include "overlayfs.h"
>
>
> @@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = {
> .update_time = ovl_update_time,
> };
>
> +static int ovl_writepages(struct address_space *mapping,
> + struct writeback_control *wbc)
> +{
> + struct inode *upper_inode = ovl_inode_upper(mapping->host);
> + struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info;
> + struct writeback_control tmp_wbc = *wbc;
> +
> + if (!ovl_should_sync(ofs))
> + return 0;
> +
> + /*
> + * for sync(2) writeback, it has a separate external IO
> + * completion path by checking PAGECACHE_TAG_WRITEBACK
> + * in pagecache, we have to set for_sync to 0 in thie case,
> + * let writeback waits completion after syncing individual
> + * dirty inode, because we haven't implemented overlayfs'
> + * own pagecache yet.
> + */
> + if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL))
> + tmp_wbc.for_sync = 0;
This looks really hacky as it closely depends on the internal details of
writeback implementation. I'd be more open to say export wait_sb_inodes()
for overlayfs use... Because that's what I gather you need in your
overlayfs ->syncfs() implementation.
Honza
> +
> + return sync_inode(upper_inode, &tmp_wbc);
> +}
> +
> static const struct address_space_operations ovl_aops = {
> + .writepages = ovl_writepages,
> /* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
> .direct_IO = noop_direct_IO,
> };
> --
> 2.26.2
>
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2020-11-02 17:17 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-25 3:41 [RFC PATCH v2 0/8] implement containerized syncfs for overlayfs Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 1/8] ovl: setup overlayfs' private bdi Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 2/8] ovl: implement ->writepages operation Chengguang Xu
2020-11-02 17:17 ` Jan Kara [this message]
2020-11-04 12:18 ` Chengguang Xu
2020-11-05 13:55 ` Jan Kara
2020-11-06 5:57 ` Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 3/8] ovl: implement overlayfs' ->evict_inode operation Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 4/8] ovl: mark overlayfs' inode dirty on modification Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 5/8] ovl: mark overlayfs' inode dirty on shared writable mmap Chengguang Xu
2020-11-02 17:30 ` Jan Kara
2020-11-04 11:54 ` Chengguang Xu
2020-11-05 14:03 ` Jan Kara
2020-11-05 14:21 ` Amir Goldstein
2020-11-05 15:54 ` Jan Kara
2020-11-06 2:41 ` Chengguang Xu
2020-11-06 8:50 ` Jan Kara
2020-11-06 9:47 ` Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 6/8] ovl: implement overlayfs' ->write_inode operation Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 7/8] ovl: cache dirty overlayfs' inode Chengguang Xu
2020-10-25 3:41 ` [RFC PATCH v2 8/8] ovl: implement containerized syncfs for overlayfs Chengguang Xu
2020-10-30 15:46 ` [RFC PATCH v2 0/8] " Miklos Szeredi
2020-10-31 12:22 ` Chengguang Xu
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