2020-03-11 00:01:22

by Qian Cai

Subject: [PATCH] page-flags: fix a crash at SetPageError(THP_SWAP)

The commit bd4c82c22c36 ("mm, THP, swap: delay splitting THP after
swapped out") supported writing THP to a swap device but forgot to
upgrade an older commit df8c94d13c7e ("page-flags: define behavior of
FS/IO-related flags on compound pages") which could trigger a crash
during THP swapping out with DEBUG_VM_PGFLAGS=y,

kernel BUG at include/linux/page-flags.h:317!

page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page))
page:fffff3b2ec3a8000 refcount:512 mapcount:0 mapping:000000009eb0338c
index:0x7f6e58200 head:fffff3b2ec3a8000 order:9 compound_mapcount:0
compound_pincount:0
anon flags:
0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked)

end_swap_bio_write()
SetPageError(page)
VM_BUG_ON_PAGE(1 && PageCompound(page))

<IRQ>
bio_endio+0x297/0x560
dec_pending+0x218/0x430 [dm_mod]
clone_endio+0xe4/0x2c0 [dm_mod]
bio_endio+0x297/0x560
blk_update_request+0x201/0x920
scsi_end_request+0x6b/0x4b0
scsi_io_completion+0x509/0x7e0
scsi_finish_command+0x1ed/0x2a0
scsi_softirq_done+0x1c9/0x1d0
__blk_mqnterrupt+0xf/0x20
</IRQ>

Fix by checking PF_NO_TAIL in those places instead.

Fixes: bd4c82c22c36 ("mm, THP, swap: delay splitting THP after swapped out")
Cc: <[email protected]>
Signed-off-by: Qian Cai <[email protected]>
---
include/linux/page-flags.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 1bf83c8fcaa7..77de28bfefb0 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -311,7 +311,7 @@ static inline int TestClearPage##uname(struct page *page) { return 0; }

__PAGEFLAG(Locked, locked, PF_NO_TAIL)
PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
-PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
+PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL)
PAGEFLAG(Referenced, referenced, PF_HEAD)
TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
__SETPAGEFLAG(Referenced, referenced, PF_HEAD)
--
2.21.0 (Apple Git-122.2)

2020-03-11 00:49:31

by Huang, Ying

Subject: Re: [PATCH] page-flags: fix a crash at SetPageError(THP_SWAP)

Qian Cai <[email protected]> writes:

> The commit bd4c82c22c36 ("mm, THP, swap: delay splitting THP after
> swapped out") supported writing THP to a swap device but forgot to
> upgrade an older commit df8c94d13c7e ("page-flags: define behavior of
> FS/IO-related flags on compound pages") which could trigger a crash
> during THP swapping out with DEBUG_VM_PGFLAGS=y,
>
> kernel BUG at include/linux/page-flags.h:317!
>
> page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page))
> page:fffff3b2ec3a8000 refcount:512 mapcount:0 mapping:000000009eb0338c
> index:0x7f6e58200 head:fffff3b2ec3a8000 order:9 compound_mapcount:0
> compound_pincount:0
> anon flags:
> 0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked)
>
> end_swap_bio_write()
> SetPageError(page)
> VM_BUG_ON_PAGE(1 && PageCompound(page))
>
> <IRQ>
> bio_endio+0x297/0x560
> dec_pending+0x218/0x430 [dm_mod]
> clone_endio+0xe4/0x2c0 [dm_mod]
> bio_endio+0x297/0x560
> blk_update_request+0x201/0x920
> scsi_end_request+0x6b/0x4b0
> scsi_io_completion+0x509/0x7e0
> scsi_finish_command+0x1ed/0x2a0
> scsi_softirq_done+0x1c9/0x1d0
> __blk_mqnterrupt+0xf/0x20
> </IRQ>
>
> Fix by checking PF_NO_TAIL in those places instead.
>
> Fixes: bd4c82c22c36 ("mm, THP, swap: delay splitting THP after swapped out")
> Cc: <[email protected]>
> Signed-off-by: Qian Cai <[email protected]>

Good catch! Thanks!

Acked-by: "Huang, Ying" <[email protected]>

> ---
> include/linux/page-flags.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 1bf83c8fcaa7..77de28bfefb0 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -311,7 +311,7 @@ static inline int TestClearPage##uname(struct page *page) { return 0; }
>
> __PAGEFLAG(Locked, locked, PF_NO_TAIL)
> PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
> -PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
> +PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL)
> PAGEFLAG(Referenced, referenced, PF_HEAD)
> TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
> __SETPAGEFLAG(Referenced, referenced, PF_HEAD)

2020-03-11 13:59:38

by David Hildenbrand

Subject: Re: [PATCH] page-flags: fix a crash at SetPageError(THP_SWAP)

On 11.03.20 00:58, Qian Cai wrote:
> The commit bd4c82c22c36 ("mm, THP, swap: delay splitting THP after
> swapped out") supported writing THP to a swap device but forgot to
> upgrade an older commit df8c94d13c7e ("page-flags: define behavior of
> FS/IO-related flags on compound pages") which could trigger a crash
> during THP swapping out with DEBUG_VM_PGFLAGS=y,
>
> kernel BUG at include/linux/page-flags.h:317!
>
> page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page))
> page:fffff3b2ec3a8000 refcount:512 mapcount:0 mapping:000000009eb0338c
> index:0x7f6e58200 head:fffff3b2ec3a8000 order:9 compound_mapcount:0
> compound_pincount:0
> anon flags:
> 0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked)
>
> end_swap_bio_write()
> SetPageError(page)
> VM_BUG_ON_PAGE(1 && PageCompound(page))
>
> <IRQ>
> bio_endio+0x297/0x560
> dec_pending+0x218/0x430 [dm_mod]
> clone_endio+0xe4/0x2c0 [dm_mod]
> bio_endio+0x297/0x560
> blk_update_request+0x201/0x920
> scsi_end_request+0x6b/0x4b0
> scsi_io_completion+0x509/0x7e0
> scsi_finish_command+0x1ed/0x2a0
> scsi_softirq_done+0x1c9/0x1d0
> __blk_mqnterrupt+0xf/0x20
> </IRQ>
>
> Fix by checking PF_NO_TAIL in those places instead.
>
> Fixes: bd4c82c22c36 ("mm, THP, swap: delay splitting THP after swapped out")
> Cc: <[email protected]>
> Signed-off-by: Qian Cai <[email protected]>
> ---
> include/linux/page-flags.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 1bf83c8fcaa7..77de28bfefb0 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -311,7 +311,7 @@ static inline int TestClearPage##uname(struct page *page) { return 0; }
>
> __PAGEFLAG(Locked, locked, PF_NO_TAIL)
> PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
> -PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
> +PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL)
> PAGEFLAG(Referenced, referenced, PF_HEAD)
> TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
> __SETPAGEFLAG(Referenced, referenced, PF_HEAD)
>

Reviewed-by: David Hildenbrand <[email protected]>

--
Thanks,

David / dhildenb

2020-03-13 21:44:44

by Rafael Aquini

Subject: Re: [PATCH] page-flags: fix a crash at SetPageError(THP_SWAP)

On Tue, Mar 10, 2020 at 07:58:46PM -0400, Qian Cai wrote:
> The commit bd4c82c22c36 ("mm, THP, swap: delay splitting THP after
> swapped out") supported writing THP to a swap device but forgot to
> upgrade an older commit df8c94d13c7e ("page-flags: define behavior of
> FS/IO-related flags on compound pages") which could trigger a crash
> during THP swapping out with DEBUG_VM_PGFLAGS=y,
>
> kernel BUG at include/linux/page-flags.h:317!
>
> page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page))
> page:fffff3b2ec3a8000 refcount:512 mapcount:0 mapping:000000009eb0338c
> index:0x7f6e58200 head:fffff3b2ec3a8000 order:9 compound_mapcount:0
> compound_pincount:0
> anon flags:
> 0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked)
>
> end_swap_bio_write()
> SetPageError(page)
> VM_BUG_ON_PAGE(1 && PageCompound(page))
>
> <IRQ>
> bio_endio+0x297/0x560
> dec_pending+0x218/0x430 [dm_mod]
> clone_endio+0xe4/0x2c0 [dm_mod]
> bio_endio+0x297/0x560
> blk_update_request+0x201/0x920
> scsi_end_request+0x6b/0x4b0
> scsi_io_completion+0x509/0x7e0
> scsi_finish_command+0x1ed/0x2a0
> scsi_softirq_done+0x1c9/0x1d0
> __blk_mqnterrupt+0xf/0x20
> </IRQ>
>
> Fix by checking PF_NO_TAIL in those places instead.
>
> Fixes: bd4c82c22c36 ("mm, THP, swap: delay splitting THP after swapped out")
> Cc: <[email protected]>
> Signed-off-by: Qian Cai <[email protected]>
> ---
> include/linux/page-flags.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 1bf83c8fcaa7..77de28bfefb0 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -311,7 +311,7 @@ static inline int TestClearPage##uname(struct page *page) { return 0; }
>
> __PAGEFLAG(Locked, locked, PF_NO_TAIL)
> PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
> -PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
> +PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL)
> PAGEFLAG(Referenced, referenced, PF_HEAD)
> TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
> __SETPAGEFLAG(Referenced, referenced, PF_HEAD)
> --
> 2.21.0 (Apple Git-122.2)
>
Acked-by: Rafael Aquini <[email protected]>