* [PATCH v2] fs/dax: Fix pmd vs pte conflict detection
@ 2019-10-21 16:29 Dan Williams
2019-10-22 7:27 ` Johannes Thumshirn
0 siblings, 1 reply; 2+ messages in thread
From: Dan Williams @ 2019-10-21 16:29 UTC (permalink / raw)
To: linux-fsdevel
Cc: Jeff Smits, Doug Nelson, stable, Jan Kara, Jeff Moyer,
Matthew Wilcox (Oracle),
linux-nvdimm, linux-kernel
Users reported a v5.3 performance regression and inability to establish
huge page mappings. A revised version of the ndctl "dax.sh" huge page
unit test identifies commit 23c84eb78375 "dax: Fix missed wakeup with
PMD faults" as the source.
Update get_unlocked_entry() to check for NULL entries before checking
the entry order, otherwise NULL is misinterpreted as a present pte
conflict. The 'order' check needs to happen before the locked check as
an unlocked entry at the wrong order must fallback to lookup the correct
order.
Reported-by: Jeff Smits <jeff.smits@intel.com>
Reported-by: Doug Nelson <doug.nelson@intel.com>
Cc: <stable@vger.kernel.org>
Fixes: 23c84eb78375 ("dax: Fix missed wakeup with PMD faults")
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
Changes in v2:
- Update the changelog to reflect the user visible effects of the bug
(Jeff)
fs/dax.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 6bf81f931de3..2cc43cd914eb 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -220,10 +220,11 @@ static void *get_unlocked_entry(struct xa_state *xas, unsigned int order)
for (;;) {
entry = xas_find_conflict(xas);
+ if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
+ return entry;
if (dax_entry_order(entry) < order)
return XA_RETRY_ENTRY;
- if (!entry || WARN_ON_ONCE(!xa_is_value(entry)) ||
- !dax_is_locked(entry))
+ if (!dax_is_locked(entry))
return entry;
wq = dax_entry_waitqueue(xas, entry, &ewait.key);
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] fs/dax: Fix pmd vs pte conflict detection
2019-10-21 16:29 [PATCH v2] fs/dax: Fix pmd vs pte conflict detection Dan Williams
@ 2019-10-22 7:27 ` Johannes Thumshirn
0 siblings, 0 replies; 2+ messages in thread
From: Johannes Thumshirn @ 2019-10-22 7:27 UTC (permalink / raw)
To: Dan Williams, linux-fsdevel
Cc: Jeff Smits, Doug Nelson, stable, Jan Kara,
Matthew Wilcox (Oracle),
linux-nvdimm, linux-kernel
Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
--
Johannes Thumshirn SUSE Labs Filesystems
jthumshirn@suse.de +49 911 74053 689
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5
90409 Nürnberg
Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
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