[PATCH] XArray: revert (unintentional?) behavior change

Partially revert commit 6684aba0780d ("XArray: Add extra debugging check
to xas_lock and friends"), fixing test failures in check_xa_alloc.

Fixes: 6684aba0780d ("XArray: Add extra debugging check to xas_lock and friends")
Signed-off-by: Tamir Duberstein <redacted>
---
Before this change:

  BUG at xa_alloc_index:57
  CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc7-next-20250321-00001-gf45bb5d4b2e8 #854 NONE
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   show_stack+0x18/0x24 (C)
   dump_stack_lvl+0x40/0x84
   dump_stack+0x18/0x24
   xa_alloc_index+0x118/0x15c
   check_xa_alloc_1+0x114/0x6e8
   check_xa_alloc+0x24/0x78
   xarray_checks+0x58/0xd4
   do_one_initcall+0x74/0x168
   do_initcall_level+0x8c/0xac
   do_initcalls+0x54/0x94
   do_basic_setup+0x18/0x24
   kernel_init_freeable+0xb8/0x120
   kernel_init+0x20/0x198
   ret_from_fork+0x10/0x20
  BUG at xa_alloc_index:57
  CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc7-next-20250321-00001-gf45bb5d4b2e8 #854 NONE
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   show_stack+0x18/0x24 (C)
   dump_stack_lvl+0x40/0x84
   dump_stack+0x18/0x24
   xa_alloc_index+0x118/0x15c
   check_xa_alloc_1+0x120/0x6e8
   check_xa_alloc+0x24/0x78
   xarray_checks+0x58/0xd4
   do_one_initcall+0x74/0x168
   do_initcall_level+0x8c/0xac
   do_initcalls+0x54/0x94
   do_basic_setup+0x18/0x24
   kernel_init_freeable+0xb8/0x120
   kernel_init+0x20/0x198
   ret_from_fork+0x10/0x20
  BUG at xa_erase_index:62
  CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc7-next-20250321-00001-gf45bb5d4b2e8 #854 NONE
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   show_stack+0x18/0x24 (C)
   dump_stack_lvl+0x40/0x84
   dump_stack+0x18/0x24
   xa_erase_index+0xb0/0xd8
   check_xa_alloc_1+0x12c/0x6e8
   check_xa_alloc+0x24/0x78
   xarray_checks+0x58/0xd4
   do_one_initcall+0x74/0x168
   do_initcall_level+0x8c/0xac
   do_initcalls+0x54/0x94
   do_basic_setup+0x18/0x24
   kernel_init_freeable+0xb8/0x120
   kernel_init+0x20/0x198
   ret_from_fork+0x10/0x20
  BUG at xa_erase_index:62
  CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc7-next-20250321-00001-gf45bb5d4b2e8 #854 NONE
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   show_stack+0x18/0x24 (C)
   dump_stack_lvl+0x40/0x84
   dump_stack+0x18/0x24
   xa_erase_index+0xb0/0xd8
   check_xa_alloc_1+0x160/0x6e8
   check_xa_alloc+0x24/0x78
   xarray_checks+0x58/0xd4
   do_one_initcall+0x74/0x168
   do_initcall_level+0x8c/0xac
   do_initcalls+0x54/0x94
   do_basic_setup+0x18/0x24
   kernel_init_freeable+0xb8/0x120
   kernel_init+0x20/0x198
   ret_from_fork+0x10/0x20
  XArray: 6782365 of 6782369 tests passed
---
 lib/xarray.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/xarray.c b/lib/xarray.c
index 261814d170d8..638c4c90e5b2 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c

@@ -2380,6 +2380,7 @@ void xa_destroy(struct xarray *xa)
 	unsigned long flags;
 	void *entry;
 
+	xas.xa_node = NULL;
 	xas_lock_irqsave(&xas, flags);
 	entry = xa_head_locked(xa);
 	RCU_INIT_POINTER(xa->xa_head, NULL);

---
base-commit: 9388ec571cb1adba59d1cded2300eeb11827679c
change-id: 20250321-xarray-fix-destroy-274090a7a18b

Best regards,
-- 
Tamir Duberstein [off-list ref]

On Fri, 21 Mar 2025 22:17:08 -0400 Tamir Duberstein [off-list ref] wrote:

Partially revert commit 6684aba0780d ("XArray: Add extra debugging check
to xas_lock and friends"), fixing test failures in check_xa_alloc.

Fixes: 6684aba0780d ("XArray: Add extra debugging check to xas_lock and friends")

Thanks.

6684aba0780d appears to be only in linux-next.  It has no Link: and my
efforts to google its origin story failed.  Help?

Hi Andrew,

On Fri, 21 Mar 2025 21:37:33 -0700 Andrew Morton [off-list ref] wrote:

On Fri, 21 Mar 2025 22:17:08 -0400 Tamir Duberstein [off-list ref] wrote:

quoted

Partially revert commit 6684aba0780d ("XArray: Add extra debugging check
to xas_lock and friends"), fixing test failures in check_xa_alloc.

Fixes: 6684aba0780d ("XArray: Add extra debugging check to xas_lock and friends")  

Thanks.

6684aba0780d appears to be only in linux-next.  It has no Link: and my
efforts to google its origin story failed.  Help?

Its been sitting in Matthew's xarray tree
(git://git.infradead.org/users/willy/xarray.git#main) since Sep 24 2024
and linux-next since then.

-- 
Cheers,
Stephen Rothwell

Le 22/03/2025 à 05:37, Andrew Morton a écrit :

On Fri, 21 Mar 2025 22:17:08 -0400 Tamir Duberstein [off-list ref] wrote:

quoted

Partially revert commit 6684aba0780d ("XArray: Add extra debugging check
to xas_lock and friends"), fixing test failures in check_xa_alloc.

Fixes: 6684aba0780d ("XArray: Add extra debugging check to xas_lock and friends")

Thanks.

6684aba0780d appears to be only in linux-next.  It has no Link: and my
efforts to google its origin story failed.  Help?

Apparently comes from git://git.infradead.org/users/willy/xarray.git

On Fri, Mar 21, 2025 at 09:37:33PM -0700, Andrew Morton wrote:

On Fri, 21 Mar 2025 22:17:08 -0400 Tamir Duberstein [off-list ref] wrote:

quoted

Partially revert commit 6684aba0780d ("XArray: Add extra debugging check
to xas_lock and friends"), fixing test failures in check_xa_alloc.

Fixes: 6684aba0780d ("XArray: Add extra debugging check to xas_lock and friends")

Thanks.

6684aba0780d appears to be only in linux-next.  It has no Link: and my
efforts to google its origin story failed.  Help?

It was added back in september to willy's tree due to an XFS data corruption bug.
See https://lore.kernel.org/linux-mm/ZvLhrF5lj3x596Qm@casper.infradead.org/ and
https://git.infradead.org/?p=users/willy/xarray.git;a=commitdiff;h=6684aba0780da9f505c202f27e68ee6d18c0aa66.

-- 
Pedro

On Fri, Mar 21, 2025 at 10:17:08PM -0400, Tamir Duberstein wrote:

Partially revert commit 6684aba0780d ("XArray: Add extra debugging check
to xas_lock and friends"), fixing test failures in check_xa_alloc.

Fixes: 6684aba0780d ("XArray: Add extra debugging check to xas_lock and friends")

This doesn't fix anything.  The first failure is:

#6  0x0000555555649979 in XAS_INVALID (xas=xas@entry=0x7ffff4a003a0)
    at ../shared/linux/../../../../include/linux/xarray.h:1434
#7  0x000055555564f545 in check_xas_retry (xa=xa@entry=0x55555591ba00 <array>)
--Type <RET> for more, q to quit, c to continue without paging--
    at ../../../lib/test_xarray.c:131
#8  0x0000555555663869 in xarray_checks () at ../../../lib/test_xarray.c:2221
#9  0x00005555556639ab in xarray_tests () at xarray.c:15

That has nothing to do with xa_destroy().  What on earth are you doing?

Anyway, I'm at LSFMM and it'a Saturday.  I shan't be looking at this
until the 27th.  There's clearly no urgency since you're the first one
to notice in six months.

On Sat, Mar 22, 2025 at 5:13 PM Matthew Wilcox [off-list ref] wrote:

On Fri, Mar 21, 2025 at 10:17:08PM -0400, Tamir Duberstein wrote:

quoted

Partially revert commit 6684aba0780d ("XArray: Add extra debugging check
to xas_lock and friends"), fixing test failures in check_xa_alloc.

Fixes: 6684aba0780d ("XArray: Add extra debugging check to xas_lock and friends")

This doesn't fix anything.  The first failure is:

#6  0x0000555555649979 in XAS_INVALID (xas=xas@entry=0x7ffff4a003a0)
    at ../shared/linux/../../../../include/linux/xarray.h:1434
#7  0x000055555564f545 in check_xas_retry (xa=xa@entry=0x55555591ba00 <array>)
--Type <RET> for more, q to quit, c to continue without paging--
    at ../../../lib/test_xarray.c:131
#8  0x0000555555663869 in xarray_checks () at ../../../lib/test_xarray.c:2221
#9  0x00005555556639ab in xarray_tests () at xarray.c:15

That's not what I see when I boot a kernel with CONFIG_TEST_XARRAY=y.

That has nothing to do with xa_destroy().  What on earth are you doing?

I'm running the kernel in a VM on arm64. What are you doing?

Anyway, I'm at LSFMM and it'a Saturday.  I shan't be looking at this
until the 27th.  There's clearly no urgency since you're the first one
to notice in six months.

Sure. I misunderstood the purpose of linux-next, thinking that if a
commit is in there then it will soon head to mainline. I realize now
this isn't the case.