Re: [PATCH v7 2/2] ceph: blocklist the kclient when receiving corrupted snap trace

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On 01/02/2023 21:12, Ilya Dryomov wrote:
On Wed, Feb 1, 2023 at 2:37 AM <xiubli@xxxxxxxxxx> wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>

When received corrupted snap trace we don't know what exactly has
happened in MDS side. And we shouldn't continue IOs and metadatas
access to MDS, which may corrupt or get incorrect contents.

This patch will just block all the further IO/MDS requests
immediately and then evict the kclient itself.

The reason why we still need to evict the kclient just after
blocking all the further IOs is that the MDS could revoke the caps
faster.

Cc: stable@xxxxxxxxxxxxxxx
URL: https://tracker.ceph.com/issues/57686
Reviewed-by: Venky Shankar <vshankar@xxxxxxxxxx>
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---
  fs/ceph/addr.c       | 17 +++++++++++++++--
  fs/ceph/caps.c       | 16 +++++++++++++---
  fs/ceph/file.c       |  9 +++++++++
  fs/ceph/mds_client.c | 28 +++++++++++++++++++++++++---
  fs/ceph/snap.c       | 38 ++++++++++++++++++++++++++++++++++++--
  fs/ceph/super.h      |  1 +
  6 files changed, 99 insertions(+), 10 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 8c74871e37c9..cac4083e387a 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -305,7 +305,7 @@ static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
         struct inode *inode = rreq->inode;
         struct ceph_inode_info *ci = ceph_inode(inode);
         struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
-       struct ceph_osd_request *req;
+       struct ceph_osd_request *req = NULL;
         struct ceph_vino vino = ceph_vino(inode);
         struct iov_iter iter;
         struct page **pages;
@@ -313,6 +313,11 @@ static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
         int err = 0;
         u64 len = subreq->len;

+       if (ceph_inode_is_shutdown(inode)) {
+               err = -EIO;
+               goto out;
+       }
+
         if (ceph_has_inline_data(ci) && ceph_netfs_issue_op_inline(subreq))
                 return;

@@ -563,6 +568,9 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)

         dout("writepage %p idx %lu\n", page, page->index);

+       if (ceph_inode_is_shutdown(inode))
+               return -EIO;
+
         /* verify this is a writeable snap context */
         snapc = page_snap_context(page);
         if (!snapc) {
@@ -1643,7 +1651,7 @@ int ceph_uninline_data(struct file *file)
         struct ceph_inode_info *ci = ceph_inode(inode);
         struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
         struct ceph_osd_request *req = NULL;
-       struct ceph_cap_flush *prealloc_cf;
+       struct ceph_cap_flush *prealloc_cf = NULL;
         struct folio *folio = NULL;
         u64 inline_version = CEPH_INLINE_NONE;
         struct page *pages[1];
@@ -1657,6 +1665,11 @@ int ceph_uninline_data(struct file *file)
         dout("uninline_data %p %llx.%llx inline_version %llu\n",
              inode, ceph_vinop(inode), inline_version);

+       if (ceph_inode_is_shutdown(inode)) {
+               err = -EIO;
+               goto out;
+       }
+
         if (inline_version == CEPH_INLINE_NONE)
                 return 0;

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index f75ad432f375..210e40037881 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -4078,6 +4078,7 @@ void ceph_handle_caps(struct ceph_mds_session *session,
         void *p, *end;
         struct cap_extra_info extra_info = {};
         bool queue_trunc;
+       bool close_sessions = false;

         dout("handle_caps from mds%d\n", session->s_mds);

@@ -4215,9 +4216,13 @@ void ceph_handle_caps(struct ceph_mds_session *session,
                 realm = NULL;
                 if (snaptrace_len) {
                         down_write(&mdsc->snap_rwsem);
-                       ceph_update_snap_trace(mdsc, snaptrace,
-                                              snaptrace + snaptrace_len,
-                                              false, &realm);
+                       if (ceph_update_snap_trace(mdsc, snaptrace,
+                                                  snaptrace + snaptrace_len,
+                                                  false, &realm)) {
+                               up_write(&mdsc->snap_rwsem);
+                               close_sessions = true;
+                               goto done;
+                       }
                         downgrade_write(&mdsc->snap_rwsem);
                 } else {
                         down_read(&mdsc->snap_rwsem);
@@ -4277,6 +4282,11 @@ void ceph_handle_caps(struct ceph_mds_session *session,
         iput(inode);
  out:
         ceph_put_string(extra_info.pool_ns);
+
+       /* Defer closing the sessions after s_mutex lock being released */
+       if (close_sessions)
+               ceph_mdsc_close_sessions(mdsc);
+
         return;

  flush_cap_releases:
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 764598e1efd9..3fbf4993d15d 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -943,6 +943,9 @@ static ssize_t ceph_sync_read(struct kiocb *iocb, struct iov_iter *to,
         dout("sync_read on file %p %llu~%u %s\n", file, off, (unsigned)len,
              (file->f_flags & O_DIRECT) ? "O_DIRECT" : "");

+       if (ceph_inode_is_shutdown(inode))
+               return -EIO;
Hi Xiubo,

ceph_sync_read() is called only from ceph_read_iter() which already
checks for ceph_inode_is_shutdown() (although the generated error is
ESTALE instead of EIO).  Is the new one in ceph_sync_read() actually
needed?

If the answer is yes, why hasn't a corresponding check been added to
ceph_sync_write()?

Before I generated this patch based on the fscrypt patches,  this will be renamed to __ceph_sync_read() and also will be called by fill_fscrypt_truncate(). I just forgot this and after rebasing I didn't adjust it.

I have updated the 'wip-snap-trace-blocklist' branch by removing it from here and ceph_direct_read_write(). And I will fix this later in the fscrypt patches.


+
         if (!len)
                 return 0;
         /*
@@ -1287,6 +1290,9 @@ ceph_direct_read_write(struct kiocb *iocb, struct iov_iter *iter,
         bool write = iov_iter_rw(iter) == WRITE;
         bool should_dirty = !write && user_backed_iter(iter);

+       if (ceph_inode_is_shutdown(inode))
+               return -EIO;
Similarly, ceph_direct_read_write() is called from ceph_read_iter() and
ceph_write_iter(), both of which check for ceph_inode_is_shutdown() at
the top already.

+
         if (write && ceph_snap(file_inode(file)) != CEPH_NOSNAP)
                 return -EROFS;

@@ -2011,6 +2017,9 @@ static int ceph_zero_partial_object(struct inode *inode,
         loff_t zero = 0;
         int op;

+       if (ceph_inode_is_shutdown(inode))
+               return -EIO;
+
         if (!length) {
                 op = offset ? CEPH_OSD_OP_DELETE : CEPH_OSD_OP_TRUNCATE;
                 length = &zero;
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 26a0a8b9975e..df78d30c1cce 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -806,6 +806,9 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
  {
         struct ceph_mds_session *s;

+       if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO)
+               return ERR_PTR(-EIO);
+
         if (mds >= mdsc->mdsmap->possible_max_rank)
                 return ERR_PTR(-EINVAL);

@@ -1478,6 +1481,9 @@ static int __open_session(struct ceph_mds_client *mdsc,
         int mstate;
         int mds = session->s_mds;

+       if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO)
+               return -EIO;
+
         /* wait for mds to go active? */
         mstate = ceph_mdsmap_get_state(mdsc->mdsmap, mds);
         dout("open_session to mds%d (%s)\n", mds,
@@ -2860,6 +2866,11 @@ static void __do_request(struct ceph_mds_client *mdsc,
                 return;
         }

+       if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO) {
+               dout("do_request metadata corrupted\n");
+               err = -EIO;
+               goto finish;
+       }
         if (req->r_timeout &&
             time_after_eq(jiffies, req->r_started + req->r_timeout)) {
                 dout("do_request timed out\n");
@@ -3245,6 +3256,7 @@ static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
         u64 tid;
         int err, result;
         int mds = session->s_mds;
+       bool close_sessions = false;

         if (msg->front.iov_len < sizeof(*head)) {
                 pr_err("mdsc_handle_reply got corrupt (short) reply\n");
@@ -3351,10 +3363,15 @@ static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
         realm = NULL;
         if (rinfo->snapblob_len) {
                 down_write(&mdsc->snap_rwsem);
-               ceph_update_snap_trace(mdsc, rinfo->snapblob,
+               err = ceph_update_snap_trace(mdsc, rinfo->snapblob,
                                 rinfo->snapblob + rinfo->snapblob_len,
                                 le32_to_cpu(head->op) == CEPH_MDS_OP_RMSNAP,
                                 &realm);
+               if (err) {
+                       up_write(&mdsc->snap_rwsem);
+                       close_sessions = true;
+                       goto out_err;
+               }
                 downgrade_write(&mdsc->snap_rwsem);
         } else {
                 down_read(&mdsc->snap_rwsem);
@@ -3412,6 +3429,10 @@ static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
                                      req->r_end_latency, err);
  out:
         ceph_mdsc_put_request(req);
+
+       /* Defer closing the sessions after s_mutex lock being released */
+       if (close_sessions)
+               ceph_mdsc_close_sessions(mdsc);
         return;
  }

@@ -5011,7 +5032,7 @@ static bool done_closing_sessions(struct ceph_mds_client *mdsc, int skipped)
  }

  /*
- * called after sb is ro.
+ * called after sb is ro or when metadata corrupted.
   */
  void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
  {
@@ -5301,7 +5322,8 @@ static void mds_peer_reset(struct ceph_connection *con)
         struct ceph_mds_client *mdsc = s->s_mdsc;

         pr_warn("mds%d closed our session\n", s->s_mds);
-       send_mds_reconnect(mdsc, s);
+       if (READ_ONCE(mdsc->fsc->mount_state) != CEPH_MOUNT_FENCE_IO)
+               send_mds_reconnect(mdsc, s);
  }

  static void mds_dispatch(struct ceph_connection *con, struct ceph_msg *msg)
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index e4151852184e..e985e4e3ed85 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -1,6 +1,7 @@
  // SPDX-License-Identifier: GPL-2.0
  #include <linux/ceph/ceph_debug.h>

+#include <linux/fs.h>
  #include <linux/sort.h>
  #include <linux/slab.h>
  #include <linux/iversion.h>
@@ -766,8 +767,10 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
         struct ceph_snap_realm *realm;
         struct ceph_snap_realm *first_realm = NULL;
         struct ceph_snap_realm *realm_to_rebuild = NULL;
+       struct ceph_client *client = mdsc->fsc->client;
         int rebuild_snapcs;
         int err = -ENOMEM;
+       int ret;
         LIST_HEAD(dirty_realms);

         lockdep_assert_held_write(&mdsc->snap_rwsem);
@@ -884,6 +887,27 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
         if (first_realm)
                 ceph_put_snap_realm(mdsc, first_realm);
         pr_err("%s error %d\n", __func__, err);
+
+       /*
+        * When receiving a corrupted snap trace we don't know what
+        * exactly has happened in MDS side. And we shouldn't continue
+        * writing to OSD, which may corrupt the snapshot contents.
+        *
+        * Just try to blocklist this kclient and then this kclient
+        * must be remounted to continue after the corrupted metadata
+        * fixed in the MDS side.
+        */
+       WRITE_ONCE(mdsc->fsc->mount_state, CEPH_MOUNT_FENCE_IO);
+       ret = ceph_monc_blocklist_add(&client->monc, &client->msgr.inst.addr);
+       if (ret)
+               pr_err("%s blocklist of %s failed: %d", __func__,
A newline is missing at the end here, I have added it.

+                      ceph_pr_addr(&client->msgr.inst.addr), ret);
+
+       WARN(1, "%s: %s%sdo remount to continue%s",
+            __func__, ret ? "" : ceph_pr_addr(&client->msgr.inst.addr),
+            ret ? "" : " was blocklisted, ",
+            err == -EIO ? " after corrupted snaptrace is fixed" : "");
+
         return err;
  }

@@ -984,6 +1008,7 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
         __le64 *split_inos = NULL, *split_realms = NULL;
         int i;
         int locked_rwsem = 0;
+       bool close_sessions = false;

         /* decode */
         if (msg->front.iov_len < sizeof(*h))
@@ -1092,8 +1117,12 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
          * update using the provided snap trace. if we are deleting a
          * snap, we can avoid queueing cap_snaps.
          */
-       ceph_update_snap_trace(mdsc, p, e,
-                              op == CEPH_SNAP_OP_DESTROY, NULL);
+       if (ceph_update_snap_trace(mdsc, p, e,
+                                  op == CEPH_SNAP_OP_DESTROY,
+                                  NULL)) {
+               close_sessions = true;
+               goto bad;
+       }

         if (op == CEPH_SNAP_OP_SPLIT)
                 /* we took a reference when we created the realm, above */
@@ -1112,6 +1141,11 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
  out:
         if (locked_rwsem)
                 up_write(&mdsc->snap_rwsem);
+
+       /* Defer closing the sessions after s_mutex lock being released */
s_mutex doesn't seem to be held here.  Did you mean snap_rwsem or does
the locking not matter at all in this case?

I assume it's the latter so I have removed this comment.  Let me know
if it needs to be added back and mention snap_rwsem (or something else
entirely) instead.

There are 3 places will do this and the other two will hold the s_mutex. But here it won't, so it's okay to remove it here.

Thanks

- Xiubo

I have pushed the result to wip-snap-trace-blocklist branch for now,
until the question of either redundant or missing checks in file.c is
clarified.

Thanks,

                 Ilya

--
Best Regards,

Xiubo Li (李秀波)

Email: xiubli@xxxxxxxxxx/xiubli@xxxxxxx
Slack: @Xiubo Li




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