From: Matthew Wilcox <willy@infradead.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
Dave Jiang <dave.jiang@intel.com>,
linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org,
stable@vger.kernel.org
Subject: [PATCH 2/2] dax: Don't access a freed inode
Date: Tue, 27 Nov 2018 13:16:34 -0800 [thread overview]
Message-ID: <20181127211634.4995-3-willy@infradead.org> (raw)
In-Reply-To: <20181127211634.4995-1-willy@infradead.org>
After we drop the i_pages lock, the inode can be freed at any time.
The get_unlocked_entry() code has no choice but to reacquire the lock,
so it can't be used here. Create a new wait_entry_unlocked() which takes
care not to acquire the lock or dereference the address_space in any way.
Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()")
Cc: stable@vger.kernel.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
fs/dax.c | 26 +++++++++++++++++++++++---
1 file changed, 23 insertions(+), 3 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index e69fc231833b..cf1805645d18 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -232,6 +232,28 @@ static void *get_unlocked_entry(struct xa_state *xas)
}
}
+/*
+ * The only thing keeping the address space around is the i_pages lock
+ * (it's cycled in clear_inode() after removing the entries from i_pages)
+ * After we call xas_unlock_irq(), we cannot touch xas->xa.
+ */
+static void wait_entry_unlocked(struct xa_state *xas, void *entry)
+{
+ struct wait_exceptional_entry_queue ewait;
+ wait_queue_head_t *wq;
+
+ init_wait(&ewait.wait);
+ ewait.wait.func = wake_exceptional_entry_func;
+
+ wq = dax_entry_waitqueue(xas, entry, &ewait.key);
+ prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
+ xas_unlock_irq(xas);
+ schedule();
+ finish_wait(wq, &ewait.wait);
+ if (waitqueue_active(wq))
+ __wake_up(wq, TASK_NORMAL, 1, &ewait.key);
+}
+
static void put_unlocked_entry(struct xa_state *xas, void *entry)
{
/* If we were the only waiter woken, wake the next one */
@@ -389,9 +411,7 @@ bool dax_lock_mapping_entry(struct page *page)
entry = xas_load(&xas);
if (dax_is_locked(entry)) {
rcu_read_unlock();
- entry = get_unlocked_entry(&xas);
- xas_unlock_irq(&xas);
- put_unlocked_entry(&xas, entry);
+ wait_entry_unlocked(&xas, entry);
rcu_read_lock();
continue;
}
--
2.19.1
next prev parent reply other threads:[~2018-11-27 21:16 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 21:16 [PATCH 0/2] Two DAX fixes for 4.20 Matthew Wilcox
2018-11-27 21:16 ` [PATCH 1/2] dax: Check page->mapping isn't NULL Matthew Wilcox
2018-11-28 9:18 ` Johannes Thumshirn
2018-11-28 11:46 ` Jan Kara
2018-11-27 21:16 ` Matthew Wilcox [this message]
2018-11-28 11:53 ` [PATCH 2/2] dax: Don't access a freed inode Jan Kara
2018-11-28 17:08 ` Dan Williams
2018-11-28 17:10 ` Matthew Wilcox
2018-11-28 19:44 ` [PATCH v2] " Dan Williams
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