Re: [PATCH] cifs: flush before set-info if we have writeable handles

[Pavel Shilovsky <piastryyy@gmail.com>]

пн, 15 июл. 2019 г. в 20:24, Ronnie Sahlberg <lsahlber@redhat.com>:
>
> Servers can defer destaging any data and updating the mtime until close().
> This means that if we do a setinfo to modify the mtime while other handles
> are open for write the server may overwrite our setinfo timestamps when
> if flushes the file on close() of the writeable handle.
>
> To avoid this we add an explicit flush() before any attempts to use setinfo
> and update the mtime IF we have writeable handles open.
>
> This makes "cp -p" preserve the mtime when copying files to some smb servers.
>
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/smb2inode.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/smb2inode.c b/fs/cifs/smb2inode.c
> index 278405d26c47..a3603ec3a086 100644
> --- a/fs/cifs/smb2inode.c
> +++ b/fs/cifs/smb2inode.c
> @@ -516,7 +516,11 @@ smb2_set_file_info(struct inode *inode, const char *full_path,
>  {
>         struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
>         struct tcon_link *tlink;
> +       struct cifs_tcon *tcon;
> +       struct TCP_Server_Info *server;
>         int rc;
> +       struct cifsInodeInfo *cifsi;
> +       struct cifsFileInfo *wrcfile;
>
>         if ((buf->CreationTime == 0) && (buf->LastAccessTime == 0) &&
>             (buf->LastWriteTime == 0) && (buf->ChangeTime == 0) &&
> @@ -527,7 +531,19 @@ smb2_set_file_info(struct inode *inode, const char *full_path,
>         if (IS_ERR(tlink))
>                 return PTR_ERR(tlink);
>
> -       rc = smb2_compound_op(xid, tlink_tcon(tlink), cifs_sb, full_path,
> +       tcon = tlink_tcon(tlink);
> +       server = tcon->ses->server;
> +
> +       if (buf->LastWriteTime) {
> +               cifsi = CIFS_I(inode);
> +               wrcfile = find_writable_file(cifsi, false);

use get_writable_file instead - this will allow us to get a real RC.
if -EBADF is returned then no writable handle and should proceed
normally, otherwise let's fail setattr.

> +               if (wrcfile) {
> +                       filemap_write_and_wait(inode->i_mapping);

If the above function returns error, the same problem that you are
trying to fix appears. If an error happen, we should fail setattr to
avoid corruption of timestamps.

> +                       server->ops->flush(xid, tcon, &wrcfile->fid);

the same logic applies to flush call - need to fail setattr if an error occured.

> +                       cifsFileInfo_put(wrcfile);
> +               }
> +       }
> +       rc = smb2_compound_op(xid, tcon, cifs_sb, full_path,
>                               FILE_WRITE_ATTRIBUTES, FILE_OPEN, 0, buf,
>                               SMB2_OP_SET_INFO);
>         cifs_put_tlink(tlink);
> --
> 2.13.6
>


--
Best regards,
Pavel Shilovsky