From: Dan Williams <dan.j.williams@intel.com> To: linux-fsdevel@vger.kernel.org Cc: Jeff Smits <jeff.smits@intel.com>, Doug Nelson <doug.nelson@intel.com>, stable@vger.kernel.org, Jan Kara <jack@suse.cz>, "Matthew Wilcox (Oracle)" <willy@infradead.org>, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] fs/dax: Fix pmd vs pte conflict detection Date: Mon, 21 Oct 2019 09:29:20 -0700 [thread overview] Message-ID: <157167532455.3945484.11971474077040503994.stgit@dwillia2-desk3.amr.corp.intel.com> (raw) 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); _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
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From: Dan Williams <dan.j.williams@intel.com> To: linux-fsdevel@vger.kernel.org Cc: Jeff Smits <jeff.smits@intel.com>, Doug Nelson <doug.nelson@intel.com>, stable@vger.kernel.org, Jan Kara <jack@suse.cz>, Jeff Moyer <jmoyer@redhat.com>, "Matthew Wilcox \(Oracle\)" <willy@infradead.org>, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] fs/dax: Fix pmd vs pte conflict detection Date: Mon, 21 Oct 2019 09:29:20 -0700 [thread overview] Message-ID: <157167532455.3945484.11971474077040503994.stgit@dwillia2-desk3.amr.corp.intel.com> (raw) 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);
next reply other threads:[~2019-10-21 19:04 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-21 16:29 Dan Williams [this message] 2019-10-21 16:29 ` [PATCH v2] fs/dax: Fix pmd vs pte conflict detection Dan Williams 2019-10-22 7:27 ` Johannes Thumshirn 2019-10-22 7:27 ` Johannes Thumshirn 2019-10-27 5:17 ` [fs/dax] a70e8083a9: fio.read_bw_MBps 523.2% improvement kernel test robot 2019-10-27 5:17 ` kernel test robot 2019-10-27 5:17 ` kernel test robot
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