Hi Al,
On Tue, 29 Jan 2013, Al Viro wrote:
> On Mon, Jan 28, 2013 at 09:20:34PM -0800, Sage Weil wrote:
>
> > Yep, that is indeed a problem. I think we just need to do the r_aborted
> > and/or r_locked_dir check in the else if condition...
> >
> > > I'm not sure if we are guaranteed that ceph_readdir_prepopulate() won't
> > > get to its splice_dentry() and d_delete() calls in similar situations -
> > > I hadn't checked that one yet. If it isn't guaranteed, we have a problem
> > > there as well.
> >
> > ...and the condition guarding readdir_prepopulate(). :)
>
> > I think you're reading it correctly. The main thing to keep in mind here
> > is that we *do* need to call fill_inode() for the inode metadata on these
> > requests to keep the mds and client state in sync. The dentry state is
> > safe to ignore.
>
> You mean the parts under
> if (rinfo->head->is_dentry) {
> and
> if (rinfo->head->is_target) {
> in there? Because there's fill_inode() called from readdir_prepopulate()
> and it's a lot more problematic than those two...
Yep, patch below.
> > It would be great to have the dir i_mutex rules summarized somewhere, even
> > if it is just a copy of the below. It took a fair bit of trial and error
> > to infer what was going on when writing this code. :)
>
> Directory ->i_mutex rules are in part documented - "what VFS guarantees
> to hold" side is in Documentation/filesystems/directory-locking. It's
> the other side ("what locks are expected to be held by callers of dcache.c
> functions") that is badly missing...
>
> > Ping me when you've pushed that branch and I'll take a look...
>
> To [email protected]:/pub/scm/linux/kernel/git/viro/vfs.git
> 01a88fa..4056362 master -> master
>
> with tentative ceph patch in the very end. Should be on git.kernel.org
> shortly...
We should drop teh mds_client.c hunk from your patch, and then do
something like the below. I'll put it in the ceph tree so we can do some
basic testing. Unfortunately, the abort case is a bit annoying to
trigger.. we'll need to write a new test for it.
Thanks-
sage
>From 80d70ef02d5277af8e1355db74fffe71f7217e76 Mon Sep 17 00:00:00 2001
From: Sage Weil <[email protected]>
Date: Tue, 29 Jan 2013 13:01:15 -0800
Subject: [PATCH] ceph: prepopulate inodes only when request is aborted
If r_aborted is true, we do not hold the dir i_mutex, and cannot touch
the dcache. However, we still need to update the inodes with the state
returned by the MDS.
Reported-by: Al Viro <[email protected]>
Signed-off-by: Sage Weil <[email protected]>
---
fs/ceph/inode.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 77b1b18..b51653e 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1195,6 +1195,39 @@ done:
/*
* Prepopulate our cache with readdir results, leases, etc.
*/
+static int readdir_prepopulate_inodes_only(struct ceph_mds_request *req,
+ struct ceph_mds_session *session)
+{
+ struct ceph_mds_reply_info_parsed *rinfo = &req->r_reply_info;
+ int i, err = 0;
+
+ for (i = 0; i < rinfo->dir_nr; i++) {
+ struct ceph_vino vino;
+ struct inode *in;
+ int rc;
+
+ vino.ino = le64_to_cpu(rinfo->dir_in[i].in->ino);
+ vino.snap = le64_to_cpu(rinfo->dir_in[i].in->snapid);
+
+ in = ceph_get_inode(req->r_dentry->d_sb, vino);
+ if (IS_ERR(in)) {
+ err = PTR_ERR(in);
+ dout("new_inode badness got %d\n", err);
+ continue;
+ }
+ rc = fill_inode(in, &rinfo->dir_in[i], NULL, session,
+ req->r_request_started, -1,
+ &req->r_caps_reservation);
+ if (rc < 0) {
+ pr_err("fill_inode badness on %p got %d\n", in, rc);
+ err = rc;
+ continue;
+ }
+ }
+
+ return err;
+}
+
int ceph_readdir_prepopulate(struct ceph_mds_request *req,
struct ceph_mds_session *session)
{
@@ -1209,6 +1242,9 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
u64 frag = le32_to_cpu(rhead->args.readdir.frag);
struct ceph_dentry_info *di;
+ if (req->r_aborted)
+ return readdir_prepopulate_inodes_only(req, session);
+
if (le32_to_cpu(rinfo->head->op) == CEPH_MDS_OP_LSSNAP) {
snapdir = ceph_get_snapdir(parent->d_inode);
parent = d_find_alias(snapdir);
--
1.7.9.5
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