From: Dan Williams <dan.j.williams@intel.com>
To: linux-fsdevel@vger.kernel.org
Cc: Jan Kara <jack@suse.cz>,
linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org,
Matthew Wilcox <willy@infradead.org>,
stable@vger.kernel.org, Ross Zwisler <zwisler@kernel.org>
Subject: [PATCH v2] filesystem-dax: Fix dax_layout_busy_page() livelock
Date: Sat, 06 Oct 2018 22:59:56 -0700 [thread overview]
Message-ID: <153889193718.3143179.3432479794012686784.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)
In the presence of multi-order entries the typical
pagevec_lookup_entries() pattern may loop forever:
while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
min(end - index, (pgoff_t)PAGEVEC_SIZE),
indices)) {
...
for (i = 0; i < pagevec_count(&pvec); i++) {
index = indices[i];
...
}
index++; /* BUG */
}
The loop updates 'index' for each index found and then increments to the
next possible page to continue the lookup. However, if the last entry in
the pagevec is multi-order then the next possible page index is more
than 1 page away. Fix this locally for the filesystem-dax case by
checking for dax-multi-order entries. Going forward new users of
multi-order entries need to be similarly careful, or we need a generic
way to report the page increment in the radix iterator.
Fixes: 5fac7408d828 ("mm, fs, dax: handle layout changes to pinned dax...")
Cc: <stable@vger.kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
Changes in v2:
* Only update nr_pages if the last entry in the pagevec is multi-order.
fs/dax.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 4becbf168b7f..0fb270f0a0ef 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -666,6 +666,8 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
min(end - index, (pgoff_t)PAGEVEC_SIZE),
indices)) {
+ pgoff_t nr_pages = 1;
+
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *pvec_ent = pvec.pages[i];
void *entry;
@@ -680,8 +682,15 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
xa_lock_irq(&mapping->i_pages);
entry = get_unlocked_mapping_entry(mapping, index, NULL);
- if (entry)
+ if (entry) {
page = dax_busy_page(entry);
+ /*
+ * Account for multi-order entries at
+ * the end of the pagevec.
+ */
+ if (i + 1 >= pagevec_count(&pvec))
+ nr_pages = 1UL << dax_radix_order(entry);
+ }
put_unlocked_mapping_entry(mapping, index, entry);
xa_unlock_irq(&mapping->i_pages);
if (page)
@@ -696,7 +705,7 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
*/
pagevec_remove_exceptionals(&pvec);
pagevec_release(&pvec);
- index++;
+ index += nr_pages;
if (page)
break;
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next reply other threads:[~2018-10-07 6:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-07 5:59 Dan Williams [this message]
2018-10-08 13:42 ` [PATCH v2] filesystem-dax: Fix dax_layout_busy_page() livelock Jan Kara
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