* [PATCH][CIFS] Use FS_RENAME_DOES_D_MOVE to minimize races in rename
@ 2020-02-26 6:35 Steve French
2020-02-26 9:22 ` Amir Goldstein
0 siblings, 1 reply; 2+ messages in thread
From: Steve French @ 2020-02-26 6:35 UTC (permalink / raw)
To: CIFS; +Cc: linux-fsdevel
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Should be safer to do the dentry move immediately after the rename
rather than later.
--
Thanks,
Steve
[-- Attachment #2: 0001-cifs-do-d_move-in-rename.patch --]
[-- Type: text/x-patch, Size: 1415 bytes --]
From c1bc75178780665716ad14b8c40a8d8e58d0f3e3 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Tue, 25 Feb 2020 18:08:54 -0600
Subject: [PATCH] cifs: do d_move in rename
It is safer to do the d_move closer to the rename to
avoid races.
Signed-off-by: Steve French <stfrench@microsoft.com>
---
fs/cifs/cifsfs.c | 4 ++--
fs/cifs/inode.c | 2 ++
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index fa77fe5258b0..94e3ed4850b5 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1018,7 +1018,7 @@ struct file_system_type cifs_fs_type = {
.name = "cifs",
.mount = cifs_do_mount,
.kill_sb = cifs_kill_sb,
- /* .fs_flags */
+ .fs_flags = FS_RENAME_DOES_D_MOVE,
};
MODULE_ALIAS_FS("cifs");
@@ -1027,7 +1027,7 @@ static struct file_system_type smb3_fs_type = {
.name = "smb3",
.mount = smb3_do_mount,
.kill_sb = cifs_kill_sb,
- /* .fs_flags */
+ .fs_flags = FS_RENAME_DOES_D_MOVE,
};
MODULE_ALIAS_FS("smb3");
MODULE_ALIAS("smb3");
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 6543465595f6..7bb7ff110dc6 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1835,6 +1835,8 @@ cifs_do_rename(const unsigned int xid, struct dentry *from_dentry,
CIFSSMBClose(xid, tcon, fid.netfid);
}
do_rename_exit:
+ if (rc == 0)
+ d_move(from_dentry, to_dentry);
cifs_put_tlink(tlink);
return rc;
}
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH][CIFS] Use FS_RENAME_DOES_D_MOVE to minimize races in rename
2020-02-26 6:35 [PATCH][CIFS] Use FS_RENAME_DOES_D_MOVE to minimize races in rename Steve French
@ 2020-02-26 9:22 ` Amir Goldstein
0 siblings, 0 replies; 2+ messages in thread
From: Amir Goldstein @ 2020-02-26 9:22 UTC (permalink / raw)
To: Steve French; +Cc: CIFS, linux-fsdevel, Al Viro
On Wed, Feb 26, 2020 at 8:37 AM Steve French <smfrench@gmail.com> wrote:
>
What sort of rename races? Is that a real/reproducible problem?
> Should be safer to do the dentry move immediately after the rename
> rather than later.
>
Looking at what "later" means, you moved d_move() before
cifs_put_tlink(tlink);
and
shrink_dcache_parent(new_dentry);
detach_mounts(new_dentry);
I suppose cifs_put_tlink() is not the issue.
It makes me wonder about shrink_dcache_parent()/detach_mounts() -
they happen for some fs before d_move() and for some fs after d_move()
I think it kind of makes sense to have them moved after dentry is
unhashed anyway? (that is after d_move()).
Thanks,
Amir.
^ permalink raw reply [flat|nested] 2+ messages in thread
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