Skip to content

L
linux
Switch branch/tag
  1. 04 Sep, 2019 5 commits
    • Bob Peterson's avatar
      gfs2: Use async glocks for rename · ad26967b
      Bob Peterson authored 
      Because s_vfs_rename_mutex is not cluster-wide, multiple nodes can
reverse the roles of which directories are "old" and which are "new" for
the purposes of rename. This can cause deadlocks where two nodes end up
waiting for each other.

There can be several layers of directory dependencies across many nodes.

This patch fixes the problem by acquiring all gfs2_rename's inode glocks
asychronously and waiting for all glocks to be acquired.  That way all
inodes are locked regardless of the order.

The timeout value for multiple asynchronous glocks is calculated to be
the total of the individual wait times for each glock times two.

Since gfs2_exchange is very similar to gfs2_rename, both functions are
patched in the same way.

A new async glock wait queue, sd_async_glock_wait, keeps a list of
waiters for these events. If gfs2's holder_wake function detects an
async holder, it wakes up any waiters for the event. The waiter only
tests whether any of its requests are still pending.

Since the glocks are sent to dlm asychronously, the wait function needs
to check to see which glocks, if any, were granted.

If a glock is granted by dlm (and therefore held), its minimum hold time
is checked and adjusted as necessary, as other glock grants do.

If the event times out, all glocks held thus far must be dequeued to
resolve any existing deadlocks.  Then, if there are any outstanding
locking requests, we need to loop around and wait for dlm to respond to
those requests too.  After we release all requests, we return -ESTALE to
the caller (vfs rename) which loops around and retries the request.

    Node1           Node2
    ---------       ---------
1.  Enqueue A       Enqueue B
2.  Enqueue B       Enqueue A
3.  A granted
6.                  B granted
7.  Wait for B
8.                  Wait for A
9.                  A times out (since Node 1 holds A)
10.                 Dequeue B (since it was granted)
11.                 Wait for all requests from DLM
12. B Granted (since Node2 released it in step 10)
13. Rename
14. Dequeue A
15.                 DLM Grants A
16.                 Dequeue A (due to the timeout and since we
                    no longer have B held for our task).
17. Dequeue B
18.                 Return -ESTALE to vfs
19.                 VFS retries the operation, goto step 1.

This release-all-locks / acquire-all-locks may slow rename / exchange
down as both nodes struggle in the same way and do the same thing.
However, this will only happen when there is contention for the same
inodes, which ought to be rare.
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
      ad26967b
    • Andreas Gruenbacher's avatar
      gfs2: create function gfs2_glock_update_hold_time · 01123cf1
      Andreas Gruenbacher authored 
      This patch moves the code that updates glock minimum hold
time to a separate function. This will be called by a future
patch.
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
      01123cf1
    • Bob Peterson's avatar
      gfs2: separate holder for rgrps in gfs2_rename · bc74aaef
      Bob Peterson authored 
      Before this patch, gfs2_rename added a holder for the rgrp glock to
its array of holders, ghs. There's nothing wrong with that, but this
patch separates it into a separate holder. This is done to ensure
it's always locked last as per the proper glock lock ordering,
and also to pave the way for a future patch in which we will
lock the non-rgrp glocks asynchronously.
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
      bc74aaef
    • Markus Elfring's avatar
      gfs2: Delete an unnecessary check before brelse() · bccaef90
      Markus Elfring authored 
      The brelse() function tests whether its argument is NULL and then
returns immediately.  Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

[The same applies to brelse() in gfs2_dir_no_add (which Coccinelle
apparently missed), so fix that as well.]
Signed-off-by: default avatarMarkus Elfring <elfring@users.sourceforge.net>
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
      bccaef90
    • Andreas Gruenbacher's avatar
      gfs2: Minor PAGE_SIZE arithmetic cleanups · 45eb0504
      Andreas Gruenbacher authored 
      Replace divisions by PAGE_SIZE with shifts by PAGE_SHIFT and similar.
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
      45eb0504
  3. 03 Sep, 2019 4 commits
  5. 09 Aug, 2019 5 commits
  7. 05 Aug, 2019 1 commit
  9. 04 Aug, 2019 10 commits
  11. 03 Aug, 2019 15 commits
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7