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authorBob Peterson <rpeterso@redhat.com>2019-11-15 16:45:41 +0100
committerAndreas Gruenbacher <agruenba@redhat.com>2019-11-15 18:21:59 +0100
commitd99724c3c36ae73ed3908f5e3f2d103a48cd9ad0 (patch)
tree9c6ced7bd5fc803ca864c78ee981ea305e9c4c39 /fs/gfs2
parentgfs2: Abort gfs2_freeze if io error is seen (diff)
downloadlinux-d99724c3c36ae73ed3908f5e3f2d103a48cd9ad0.tar.xz
linux-d99724c3c36ae73ed3908f5e3f2d103a48cd9ad0.zip
gfs2: Close timing window with GLF_INVALIDATE_IN_PROGRESS
This patch closes a timing window in which two processes compete and overlap in the execution of do_xmote for the same glock: Process A Process B ------------------------------------ ----------------------------- 1. Grabs gl_lockref and calls do_xmote 2. Grabs gl_lockref but is blocked 3. Sets GLF_INVALIDATE_IN_PROGRESS 4. Unlocks gl_lockref 5. Calls do_xmote 6. Call glops->go_sync 7. test_and_clear_bit GLF_DIRTY 8. Call gfs2_log_flush Call glops->go_sync 9. (slow IO, so it blocks a long time) test_and_clear_bit GLF_DIRTY It's not dirty (step 7) returns 10. Tests GLF_INVALIDATE_IN_PROGRESS 11. Calls go_inval (rgrp_go_inval) 12. gfs2_rgrp_relse does brelse 13. truncate_inode_pages_range 14. Calls lm_lock UN In step 14 we've just told dlm to give the glock to another node when, in fact, process A has not finished the IO and synced all buffer_heads to disk and make sure their revokes are done. This patch fixes the problem by changing the GLF_INVALIDATE_IN_PROGRESS to use test_and_set_bit, and if the bit is already set, process B just ignores it and trusts that process A will do the do_xmote in the proper order. Signed-off-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Diffstat (limited to 'fs/gfs2')
-rw-r--r--fs/gfs2/glock.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index faa88bd594e2..b7123de7c180 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -558,7 +558,14 @@ __acquires(&gl->gl_lockref.lock)
GLOCK_BUG_ON(gl, gl->gl_state == gl->gl_target);
if ((target == LM_ST_UNLOCKED || target == LM_ST_DEFERRED) &&
glops->go_inval) {
- set_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
+ /*
+ * If another process is already doing the invalidate, let that
+ * finish first. The glock state machine will get back to this
+ * holder again later.
+ */
+ if (test_and_set_bit(GLF_INVALIDATE_IN_PROGRESS,
+ &gl->gl_flags))
+ return;
do_error(gl, 0); /* Fail queued try locks */
}
gl->gl_req = target;