* Re: FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree
[not found] <1544536809243247@kroah.com>
@ 2018-12-11 15:23 ` Matthew Wilcox
2018-12-14 7:13 ` Greg KH
0 siblings, 1 reply; 5+ messages in thread
From: Matthew Wilcox @ 2018-12-11 15:23 UTC (permalink / raw)
To: gregkh; +Cc: jack, stable, linux-nvdimm
On Tue, Dec 11, 2018 at 03:00:09PM +0100, gregkh@linuxfoundation.org wrote:
>
> The patch below does not apply to the 4.19-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
I have only compile-tested this backport. Dan, do you want to run it
through some tests before Greg applies it?
>From e01d37913b5577acaa2e8e35200081eae2795087 Mon Sep 17 00:00:00 2001
From: Matthew Wilcox <willy@infradead.org>
Date: Tue, 11 Dec 2018 10:16:45 -0500
Subject: [PATCH 2/2] dax: Don't access a freed inode
commit 55e56f06ed71d9441f3abd5b1d3c1a870812b3fe upstream.
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>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
fs/dax.c | 69 ++++++++++++++++++++++++++------------------------------
1 file changed, 32 insertions(+), 37 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 3a2682a6c832..415605fafaeb 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -229,8 +229,8 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
*
* Must be called with the i_pages lock held.
*/
-static void *__get_unlocked_mapping_entry(struct address_space *mapping,
- pgoff_t index, void ***slotp, bool (*wait_fn)(void))
+static void *get_unlocked_mapping_entry(struct address_space *mapping,
+ pgoff_t index, void ***slotp)
{
void *entry, **slot;
struct wait_exceptional_entry_queue ewait;
@@ -240,8 +240,6 @@ static void *__get_unlocked_mapping_entry(struct address_space *mapping,
ewait.wait.func = wake_exceptional_entry_func;
for (;;) {
- bool revalidate;
-
entry = __radix_tree_lookup(&mapping->i_pages, index, NULL,
&slot);
if (!entry ||
@@ -256,30 +254,39 @@ static void *__get_unlocked_mapping_entry(struct address_space *mapping,
prepare_to_wait_exclusive(wq, &ewait.wait,
TASK_UNINTERRUPTIBLE);
xa_unlock_irq(&mapping->i_pages);
- revalidate = wait_fn();
+ schedule();
finish_wait(wq, &ewait.wait);
xa_lock_irq(&mapping->i_pages);
- if (revalidate) {
- put_unlocked_mapping_entry(mapping, index, entry);
- return ERR_PTR(-EAGAIN);
- }
}
}
-static bool entry_wait(void)
+/*
+ * 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 address_space *mapping, pgoff_t index,
+ void ***slotp, 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(mapping, index, entry, &ewait.key);
+ prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
+ xa_unlock_irq(&mapping->i_pages);
schedule();
+ finish_wait(wq, &ewait.wait);
+
/*
- * Never return an ERR_PTR() from
- * __get_unlocked_mapping_entry(), just keep looping.
+ * Entry lock waits are exclusive. Wake up the next waiter since
+ * we aren't sure we will acquire the entry lock and thus wake
+ * the next waiter up on unlock.
*/
- return false;
-}
-
-static void *get_unlocked_mapping_entry(struct address_space *mapping,
- pgoff_t index, void ***slotp)
-{
- return __get_unlocked_mapping_entry(mapping, index, slotp, entry_wait);
+ if (waitqueue_active(wq))
+ __wake_up(wq, TASK_NORMAL, 1, &ewait.key);
}
static void unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
@@ -398,19 +405,6 @@ static struct page *dax_busy_page(void *entry)
return NULL;
}
-static bool entry_wait_revalidate(void)
-{
- rcu_read_unlock();
- schedule();
- rcu_read_lock();
-
- /*
- * Tell __get_unlocked_mapping_entry() to take a break, we need
- * to revalidate page->mapping after dropping locks
- */
- return true;
-}
-
bool dax_lock_mapping_entry(struct page *page)
{
pgoff_t index;
@@ -446,14 +440,15 @@ bool dax_lock_mapping_entry(struct page *page)
}
index = page->index;
- entry = __get_unlocked_mapping_entry(mapping, index, &slot,
- entry_wait_revalidate);
+ entry = __radix_tree_lookup(&mapping->i_pages, index,
+ NULL, &slot);
if (!entry) {
xa_unlock_irq(&mapping->i_pages);
break;
- } else if (IS_ERR(entry)) {
- xa_unlock_irq(&mapping->i_pages);
- WARN_ON_ONCE(PTR_ERR(entry) != -EAGAIN);
+ } else if (slot_locked(mapping, slot)) {
+ rcu_read_unlock();
+ wait_entry_unlocked(mapping, index, &slot, entry);
+ rcu_read_lock();
continue;
}
lock_slot(mapping, slot);
--
2.19.1
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree
2018-12-11 15:23 ` FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree Matthew Wilcox
@ 2018-12-14 7:13 ` Greg KH
2018-12-21 20:31 ` Dan Williams
0 siblings, 1 reply; 5+ messages in thread
From: Greg KH @ 2018-12-14 7:13 UTC (permalink / raw)
To: Matthew Wilcox; +Cc: jack, stable, linux-nvdimm
On Tue, Dec 11, 2018 at 07:23:49AM -0800, Matthew Wilcox wrote:
> On Tue, Dec 11, 2018 at 03:00:09PM +0100, gregkh@linuxfoundation.org wrote:
> >
> > The patch below does not apply to the 4.19-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
>
> I have only compile-tested this backport. Dan, do you want to run it
> through some tests before Greg applies it?
Thanks for the backport, I'll wait to hear from Dan before queueing this
up.
greg k-h
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree
2018-12-14 7:13 ` Greg KH
@ 2018-12-21 20:31 ` Dan Williams
2018-12-22 19:04 ` Sasha Levin
0 siblings, 1 reply; 5+ messages in thread
From: Dan Williams @ 2018-12-21 20:31 UTC (permalink / raw)
To: Greg KH; +Cc: Jan Kara, stable, Matthew Wilcox, linux-nvdimm
On Thu, Dec 13, 2018 at 11:14 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Dec 11, 2018 at 07:23:49AM -0800, Matthew Wilcox wrote:
> > On Tue, Dec 11, 2018 at 03:00:09PM +0100, gregkh@linuxfoundation.org wrote:
> > >
> > > The patch below does not apply to the 4.19-stable tree.
> > > If someone wants it applied there, or to any other stable or longterm
> > > tree, then please email the backport, including the original git commit
> > > id to <stable@vger.kernel.org>.
> >
> > I have only compile-tested this backport. Dan, do you want to run it
> > through some tests before Greg applies it?
>
> Thanks for the backport, I'll wait to hear from Dan before queueing this
> up.
Tested-by: Dan Williams <dan.j.williams@intel.com>
However, on the upstream version of this fix Linus pointed out an
additional fixup. Once that goes upstream [1] I'll circle back to
provide a fixed up version of this backport to keep -stable and
mainline more aligned.
[1]: https://marc.info/?l=linux-fsdevel&m=154542184202064&w=2
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree
2018-12-21 20:31 ` Dan Williams
@ 2018-12-22 19:04 ` Sasha Levin
2018-12-22 19:33 ` Dan Williams
0 siblings, 1 reply; 5+ messages in thread
From: Sasha Levin @ 2018-12-22 19:04 UTC (permalink / raw)
To: Dan Williams; +Cc: Greg KH, Jan Kara, stable, Matthew Wilcox, linux-nvdimm
On Fri, Dec 21, 2018 at 12:31:02PM -0800, Dan Williams wrote:
>On Thu, Dec 13, 2018 at 11:14 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>>
>> On Tue, Dec 11, 2018 at 07:23:49AM -0800, Matthew Wilcox wrote:
>> > On Tue, Dec 11, 2018 at 03:00:09PM +0100, gregkh@linuxfoundation.org wrote:
>> > >
>> > > The patch below does not apply to the 4.19-stable tree.
>> > > If someone wants it applied there, or to any other stable or longterm
>> > > tree, then please email the backport, including the original git commit
>> > > id to <stable@vger.kernel.org>.
>> >
>> > I have only compile-tested this backport. Dan, do you want to run it
>> > through some tests before Greg applies it?
>>
>> Thanks for the backport, I'll wait to hear from Dan before queueing this
>> up.
>
>Tested-by: Dan Williams <dan.j.williams@intel.com>
>
>However, on the upstream version of this fix Linus pointed out an
>additional fixup. Once that goes upstream [1] I'll circle back to
>provide a fixed up version of this backport to keep -stable and
>mainline more aligned.
>
>[1]: https://marc.info/?l=linux-fsdevel&m=154542184202064&w=2
Okay, I guess it makes sense to wait for the fixup before we pull this
backport in?
--
Thanks,
Sasha
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree
2018-12-22 19:04 ` Sasha Levin
@ 2018-12-22 19:33 ` Dan Williams
0 siblings, 0 replies; 5+ messages in thread
From: Dan Williams @ 2018-12-22 19:33 UTC (permalink / raw)
To: Sasha Levin; +Cc: Greg KH, Jan Kara, stable, Matthew Wilcox, linux-nvdimm
On Sat, Dec 22, 2018 at 11:04 AM Sasha Levin <sashal@kernel.org> wrote:
>
> On Fri, Dec 21, 2018 at 12:31:02PM -0800, Dan Williams wrote:
> >On Thu, Dec 13, 2018 at 11:14 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> >>
> >> On Tue, Dec 11, 2018 at 07:23:49AM -0800, Matthew Wilcox wrote:
> >> > On Tue, Dec 11, 2018 at 03:00:09PM +0100, gregkh@linuxfoundation.org wrote:
> >> > >
> >> > > The patch below does not apply to the 4.19-stable tree.
> >> > > If someone wants it applied there, or to any other stable or longterm
> >> > > tree, then please email the backport, including the original git commit
> >> > > id to <stable@vger.kernel.org>.
> >> >
> >> > I have only compile-tested this backport. Dan, do you want to run it
> >> > through some tests before Greg applies it?
> >>
> >> Thanks for the backport, I'll wait to hear from Dan before queueing this
> >> up.
> >
> >Tested-by: Dan Williams <dan.j.williams@intel.com>
> >
> >However, on the upstream version of this fix Linus pointed out an
> >additional fixup. Once that goes upstream [1] I'll circle back to
> >provide a fixed up version of this backport to keep -stable and
> >mainline more aligned.
> >
> >[1]: https://marc.info/?l=linux-fsdevel&m=154542184202064&w=2
>
> Okay, I guess it makes sense to wait for the fixup before we pull this
> backport in?
Yes, I'll send a replacement once mainline has that change.
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2018-12-11 15:23 ` FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree Matthew Wilcox
2018-12-14 7:13 ` Greg KH
2018-12-21 20:31 ` Dan Williams
2018-12-22 19:04 ` Sasha Levin
2018-12-22 19:33 ` Dan Williams
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