* [PATCH v4] mm: Use a folio in the softleaf_is_device_private path
@ 2026-08-03 3:15 Hongfu Li
2026-08-03 6:25 ` Anshuman Khandual
2026-08-17 15:52 ` David Hildenbrand (Arm)
0 siblings, 2 replies; 5+ messages in thread
From: Hongfu Li @ 2026-08-03 3:15 UTC (permalink / raw)
To: akpm, david, ljs, liam, vbabka, rppt, surenb, mhocko
Cc: linux-mm, linux-kernel, hongfu.li, Hongfu Li
From: Hongfu Li <lihongfu@kylinos.cn>
Use the folio APIs in the device_private migration path of do_swap_page(),
replacing four calls to compound_head() with one.
Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
v4:
- Drop the do_non_swap_page() extraction (patch 2/2 from v2)
- Added Reviewed-by: Lorenzo Stoakes
- Link to v2: https://lore.kernel.org/all/20260723030752.16979-1-hongfu.li@linux.dev/
v3:
- Please ignore v3.
v2:
- Drop fault_folio, reuse the existing folio variable instead
- Refresh commit messages
- Update comment to use "folio" instead of "page" in the
device_private path
- Add Acked-by: David Hildenbrand
- Add patch 2/2 to extract do_non_swap_page() from do_swap_page()
- Link to v1: https://lore.kernel.org/all/20260721013347.65698-1-hongfu.li@linux.dev/
---
mm/memory.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 56b244552f13..bbb289ba09d3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4873,18 +4873,19 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
goto unlock;
/*
- * Get a page reference while we know the page can't be
+ * Get a folio reference while we know the folio can't be
* freed.
*/
- if (trylock_page(vmf->page)) {
+ folio = page_folio(vmf->page);
+ if (folio_trylock(folio)) {
struct dev_pagemap *pgmap;
- get_page(vmf->page);
+ folio_get(folio);
pte_unmap_unlock(vmf->pte, vmf->ptl);
pgmap = page_pgmap(vmf->page);
ret = pgmap->ops->migrate_to_ram(vmf);
- unlock_page(vmf->page);
- put_page(vmf->page);
+ folio_unlock(folio);
+ folio_put(folio);
} else {
pte_unmap(vmf->pte);
softleaf_entry_wait_on_locked(entry, vmf->ptl);
--
2.54.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v4] mm: Use a folio in the softleaf_is_device_private path
2026-08-03 3:15 [PATCH v4] mm: Use a folio in the softleaf_is_device_private path Hongfu Li
@ 2026-08-03 6:25 ` Anshuman Khandual
2026-08-17 15:52 ` David Hildenbrand (Arm)
1 sibling, 0 replies; 5+ messages in thread
From: Anshuman Khandual @ 2026-08-03 6:25 UTC (permalink / raw)
To: Hongfu Li
Cc: akpm, david, ljs, liam, vbabka, rppt, surenb, mhocko, linux-mm,
linux-kernel, Hongfu Li
On Mon, Aug 03, 2026 at 11:15:54AM +0800, Hongfu Li wrote:
> From: Hongfu Li <lihongfu@kylinos.cn>
>
> Use the folio APIs in the device_private migration path of do_swap_page(),
> replacing four calls to compound_head() with one.
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Anshumman Khandual <anshuman.khandual@arm.com>
> ---
> v4:
> - Drop the do_non_swap_page() extraction (patch 2/2 from v2)
> - Added Reviewed-by: Lorenzo Stoakes
> - Link to v2: https://lore.kernel.org/all/20260723030752.16979-1-hongfu.li@linux.dev/
> v3:
> - Please ignore v3.
> v2:
> - Drop fault_folio, reuse the existing folio variable instead
> - Refresh commit messages
> - Update comment to use "folio" instead of "page" in the
> device_private path
> - Add Acked-by: David Hildenbrand
> - Add patch 2/2 to extract do_non_swap_page() from do_swap_page()
> - Link to v1: https://lore.kernel.org/all/20260721013347.65698-1-hongfu.li@linux.dev/
> ---
> mm/memory.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 56b244552f13..bbb289ba09d3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4873,18 +4873,19 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> goto unlock;
>
> /*
> - * Get a page reference while we know the page can't be
> + * Get a folio reference while we know the folio can't be
> * freed.
> */
> - if (trylock_page(vmf->page)) {
> + folio = page_folio(vmf->page);
> + if (folio_trylock(folio)) {
> struct dev_pagemap *pgmap;
>
> - get_page(vmf->page);
> + folio_get(folio);
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> pgmap = page_pgmap(vmf->page);
> ret = pgmap->ops->migrate_to_ram(vmf);
> - unlock_page(vmf->page);
> - put_page(vmf->page);
> + folio_unlock(folio);
> + folio_put(folio);
> } else {
> pte_unmap(vmf->pte);
> softleaf_entry_wait_on_locked(entry, vmf->ptl);
> --
> 2.54.0
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v4] mm: Use a folio in the softleaf_is_device_private path
2026-08-03 3:15 [PATCH v4] mm: Use a folio in the softleaf_is_device_private path Hongfu Li
2026-08-03 6:25 ` Anshuman Khandual
@ 2026-08-17 15:52 ` David Hildenbrand (Arm)
2026-08-17 15:57 ` David Hildenbrand (Arm)
1 sibling, 1 reply; 5+ messages in thread
From: David Hildenbrand (Arm) @ 2026-08-17 15:52 UTC (permalink / raw)
To: Hongfu Li, akpm, ljs, liam, vbabka, rppt, surenb, mhocko
Cc: linux-mm, linux-kernel, Hongfu Li
On 8/3/26 05:15, Hongfu Li wrote:
> From: Hongfu Li <lihongfu@kylinos.cn>
>
> Use the folio APIs in the device_private migration path of do_swap_page(),
> replacing four calls to compound_head() with one.
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> ---
> v4:
> - Drop the do_non_swap_page() extraction (patch 2/2 from v2)
> - Added Reviewed-by: Lorenzo Stoakes
> - Link to v2: https://lore.kernel.org/all/20260723030752.16979-1-hongfu.li@linux.dev/
> v3:
> - Please ignore v3.
> v2:
> - Drop fault_folio, reuse the existing folio variable instead
> - Refresh commit messages
> - Update comment to use "folio" instead of "page" in the
> device_private path
> - Add Acked-by: David Hildenbrand
> - Add patch 2/2 to extract do_non_swap_page() from do_swap_page()
> - Link to v1: https://lore.kernel.org/all/20260721013347.65698-1-hongfu.li@linux.dev/
> ---
> mm/memory.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 56b244552f13..bbb289ba09d3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4873,18 +4873,19 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> goto unlock;
>
> /*
> - * Get a page reference while we know the page can't be
> + * Get a folio reference while we know the folio can't be
> * freed.
> */
> - if (trylock_page(vmf->page)) {
> + folio = page_folio(vmf->page);
> + if (folio_trylock(folio)) {
> struct dev_pagemap *pgmap;
>
> - get_page(vmf->page);
> + folio_get(folio);
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> pgmap = page_pgmap(vmf->page);
> ret = pgmap->ops->migrate_to_ram(vmf);
> - unlock_page(vmf->page);
> - put_page(vmf->page);
> + folio_unlock(folio);
> + folio_put(folio);
> } else {
> pte_unmap(vmf->pte);
> softleaf_entry_wait_on_locked(entry, vmf->ptl);
Okay, so this breaks the HMM selftests:
# ok 30 hmm.hmm_device_private.migrate_anon_huge_fault
# # RUN hmm.hmm_device_private.migrate_partial_unmap_fault ...
[ 14.589125] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
[ 14.589178] Modules linked in: test_hmm
[ 14.589203] CPU: 25 UID: 0 PID: 653 Comm: hmm-tests Not tainted 7.2.0-rc5+ #14 PREEMPT
[ 14.589243] Hardware name: linux,dummy-virt (DT)
[ 14.589268] pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
[ 14.589300] pc : folio_unlock+0x78/0x88
[ 14.589326] lr : folio_unlock+0x78/0x88
[ 14.589349] sp : ffff80008284bb90
[ 14.589368] x29: ffff80008284bb90 x28: ffff0000cc8ce180 x27: 0000000000000000
[ 14.589406] x26: 0000000000000000 x25: ffff0000ca395dc0 x24: 0000000000000000
[ 14.589447] x23: 0000000020100073 x22: ffff0000c23d35c0 x21: ffffffffbfff8000
[ 14.589485] x20: ffffffffbfff8000 x19: ffff80008284bca0 x18: 0000000000000010
[ 14.589523] x17: 3030303030303030 x16: 2066666666666666 x15: 6630303030303030
[ 14.589562] x14: 0000000000000000 x13: 29296f696c6f6628 x12: 64656b636f6c5f74
[ 14.589603] x11: fffffffffffc7100 x10: fffffffffffc70b0 x9 : ffffb0504ff88f70
[ 14.589640] x8 : 3fffffffffffdfff x7 : ffff000c79b24bc0 x6 : 00000000000001a7
[ 14.589680] x5 : ffff000c79b24bc0 x4 : 0000000000000000 x3 : 0000000000000000
[ 14.589718] x2 : 0000000000000000 x1 : ffff0000cc8ce180 x0 : 000000000000003f
[ 14.589756] Call trace:
[ 14.589769] folio_unlock+0x78/0x88 (P)
[ 14.589792] do_swap_page+0xf40/0x1580
[ 14.589815] __handle_mm_fault+0x648/0xe68
[ 14.589838] handle_mm_fault+0x9c/0x330
[ 14.589858] do_page_fault+0x268/0x7e0
[ 14.589882] do_translation_fault+0x5c/0x80
[ 14.589904] do_mem_abort+0x48/0xa0
[ 14.589927] el0_da+0x38/0xd0
[ 14.589948] el0t_64_sync_handler+0xd0/0xe8
[ 14.589970] el0t_64_sync+0x198/0x1a0
[ 14.589990] Code: d65f03c0 d000eec1 913c4021 94015993 (d4210000)
I can only speculate that we need another
folio = page_folio(vmf->page);
after the migrate_to_ram() call.
Let me try that real quick.
--
Cheers,
David
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v4] mm: Use a folio in the softleaf_is_device_private path
2026-08-17 15:52 ` David Hildenbrand (Arm)
@ 2026-08-17 15:57 ` David Hildenbrand (Arm)
2026-08-17 16:39 ` Lorenzo Stoakes (ARM)
0 siblings, 1 reply; 5+ messages in thread
From: David Hildenbrand (Arm) @ 2026-08-17 15:57 UTC (permalink / raw)
To: Hongfu Li, akpm, ljs, liam, vbabka, rppt, surenb, mhocko
Cc: linux-mm, linux-kernel, Hongfu Li
On 8/17/26 17:52, David Hildenbrand (Arm) wrote:
> On 8/3/26 05:15, Hongfu Li wrote:
>> From: Hongfu Li <lihongfu@kylinos.cn>
>>
>> Use the folio APIs in the device_private migration path of do_swap_page(),
>> replacing four calls to compound_head() with one.
>>
>> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
>> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
>> Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
>> ---
>> v4:
>> - Drop the do_non_swap_page() extraction (patch 2/2 from v2)
>> - Added Reviewed-by: Lorenzo Stoakes
>> - Link to v2: https://lore.kernel.org/all/20260723030752.16979-1-hongfu.li@linux.dev/
>> v3:
>> - Please ignore v3.
>> v2:
>> - Drop fault_folio, reuse the existing folio variable instead
>> - Refresh commit messages
>> - Update comment to use "folio" instead of "page" in the
>> device_private path
>> - Add Acked-by: David Hildenbrand
>> - Add patch 2/2 to extract do_non_swap_page() from do_swap_page()
>> - Link to v1: https://lore.kernel.org/all/20260721013347.65698-1-hongfu.li@linux.dev/
>> ---
>> mm/memory.c | 11 ++++++-----
>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 56b244552f13..bbb289ba09d3 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -4873,18 +4873,19 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>> goto unlock;
>>
>> /*
>> - * Get a page reference while we know the page can't be
>> + * Get a folio reference while we know the folio can't be
>> * freed.
>> */
>> - if (trylock_page(vmf->page)) {
>> + folio = page_folio(vmf->page);
>> + if (folio_trylock(folio)) {
>> struct dev_pagemap *pgmap;
>>
>> - get_page(vmf->page);
>> + folio_get(folio);
>> pte_unmap_unlock(vmf->pte, vmf->ptl);
>> pgmap = page_pgmap(vmf->page);
>> ret = pgmap->ops->migrate_to_ram(vmf);
>> - unlock_page(vmf->page);
>> - put_page(vmf->page);
>> + folio_unlock(folio);
>> + folio_put(folio);
>> } else {
>> pte_unmap(vmf->pte);
>> softleaf_entry_wait_on_locked(entry, vmf->ptl);
>
> Okay, so this breaks the HMM selftests:
>
> # ok 30 hmm.hmm_device_private.migrate_anon_huge_fault
> # # RUN hmm.hmm_device_private.migrate_partial_unmap_fault ...
> [ 14.589125] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
> [ 14.589178] Modules linked in: test_hmm
> [ 14.589203] CPU: 25 UID: 0 PID: 653 Comm: hmm-tests Not tainted 7.2.0-rc5+ #14 PREEMPT
> [ 14.589243] Hardware name: linux,dummy-virt (DT)
> [ 14.589268] pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> [ 14.589300] pc : folio_unlock+0x78/0x88
> [ 14.589326] lr : folio_unlock+0x78/0x88
> [ 14.589349] sp : ffff80008284bb90
> [ 14.589368] x29: ffff80008284bb90 x28: ffff0000cc8ce180 x27: 0000000000000000
> [ 14.589406] x26: 0000000000000000 x25: ffff0000ca395dc0 x24: 0000000000000000
> [ 14.589447] x23: 0000000020100073 x22: ffff0000c23d35c0 x21: ffffffffbfff8000
> [ 14.589485] x20: ffffffffbfff8000 x19: ffff80008284bca0 x18: 0000000000000010
> [ 14.589523] x17: 3030303030303030 x16: 2066666666666666 x15: 6630303030303030
> [ 14.589562] x14: 0000000000000000 x13: 29296f696c6f6628 x12: 64656b636f6c5f74
> [ 14.589603] x11: fffffffffffc7100 x10: fffffffffffc70b0 x9 : ffffb0504ff88f70
> [ 14.589640] x8 : 3fffffffffffdfff x7 : ffff000c79b24bc0 x6 : 00000000000001a7
> [ 14.589680] x5 : ffff000c79b24bc0 x4 : 0000000000000000 x3 : 0000000000000000
> [ 14.589718] x2 : 0000000000000000 x1 : ffff0000cc8ce180 x0 : 000000000000003f
> [ 14.589756] Call trace:
> [ 14.589769] folio_unlock+0x78/0x88 (P)
> [ 14.589792] do_swap_page+0xf40/0x1580
> [ 14.589815] __handle_mm_fault+0x648/0xe68
> [ 14.589838] handle_mm_fault+0x9c/0x330
> [ 14.589858] do_page_fault+0x268/0x7e0
> [ 14.589882] do_translation_fault+0x5c/0x80
> [ 14.589904] do_mem_abort+0x48/0xa0
> [ 14.589927] el0_da+0x38/0xd0
> [ 14.589948] el0t_64_sync_handler+0xd0/0xe8
> [ 14.589970] el0t_64_sync+0x198/0x1a0
> [ 14.589990] Code: d65f03c0 d000eec1 913c4021 94015993 (d4210000)
>
> I can only speculate that we need another
>
> folio = page_folio(vmf->page);
>
> after the migrate_to_ram() call.
>
> Let me try that real quick.
>
Yeah, that fixes it:
diff --git a/mm/memory.c b/mm/memory.c
index 4134ac607ee0..83d1a2be957c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4937,6 +4937,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
pte_unmap_unlock(vmf->pte, vmf->ptl);
pgmap = page_pgmap(vmf->page);
ret = pgmap->ops->migrate_to_ram(vmf);
+ folio = page_folio(vmf->page);
folio_unlock(folio);
folio_put(folio);
} else {
--
Cheers,
David
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v4] mm: Use a folio in the softleaf_is_device_private path
2026-08-17 15:57 ` David Hildenbrand (Arm)
@ 2026-08-17 16:39 ` Lorenzo Stoakes (ARM)
0 siblings, 0 replies; 5+ messages in thread
From: Lorenzo Stoakes (ARM) @ 2026-08-17 16:39 UTC (permalink / raw)
To: David Hildenbrand (Arm)
Cc: Hongfu Li, akpm, liam, vbabka, rppt, surenb, mhocko, linux-mm,
linux-kernel, Hongfu Li
On Mon, Aug 17, 2026 at 05:57:57PM +0200, David Hildenbrand (Arm) wrote:
> On 8/17/26 17:52, David Hildenbrand (Arm) wrote:
> > On 8/3/26 05:15, Hongfu Li wrote:
> >> From: Hongfu Li <lihongfu@kylinos.cn>
> >>
> >> Use the folio APIs in the device_private migration path of do_swap_page(),
> >> replacing four calls to compound_head() with one.
> >>
> >> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
> >> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> >> Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> >> ---
> >> v4:
> >> - Drop the do_non_swap_page() extraction (patch 2/2 from v2)
> >> - Added Reviewed-by: Lorenzo Stoakes
> >> - Link to v2: https://lore.kernel.org/all/20260723030752.16979-1-hongfu.li@linux.dev/
> >> v3:
> >> - Please ignore v3.
> >> v2:
> >> - Drop fault_folio, reuse the existing folio variable instead
> >> - Refresh commit messages
> >> - Update comment to use "folio" instead of "page" in the
> >> device_private path
> >> - Add Acked-by: David Hildenbrand
> >> - Add patch 2/2 to extract do_non_swap_page() from do_swap_page()
> >> - Link to v1: https://lore.kernel.org/all/20260721013347.65698-1-hongfu.li@linux.dev/
> >> ---
> >> mm/memory.c | 11 ++++++-----
> >> 1 file changed, 6 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/mm/memory.c b/mm/memory.c
> >> index 56b244552f13..bbb289ba09d3 100644
> >> --- a/mm/memory.c
> >> +++ b/mm/memory.c
> >> @@ -4873,18 +4873,19 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> >> goto unlock;
> >>
> >> /*
> >> - * Get a page reference while we know the page can't be
> >> + * Get a folio reference while we know the folio can't be
> >> * freed.
> >> */
> >> - if (trylock_page(vmf->page)) {
> >> + folio = page_folio(vmf->page);
> >> + if (folio_trylock(folio)) {
> >> struct dev_pagemap *pgmap;
> >>
> >> - get_page(vmf->page);
> >> + folio_get(folio);
> >> pte_unmap_unlock(vmf->pte, vmf->ptl);
> >> pgmap = page_pgmap(vmf->page);
> >> ret = pgmap->ops->migrate_to_ram(vmf);
> >> - unlock_page(vmf->page);
> >> - put_page(vmf->page);
> >> + folio_unlock(folio);
> >> + folio_put(folio);
> >> } else {
> >> pte_unmap(vmf->pte);
> >> softleaf_entry_wait_on_locked(entry, vmf->ptl);
> >
> > Okay, so this breaks the HMM selftests:
> >
> > # ok 30 hmm.hmm_device_private.migrate_anon_huge_fault
> > # # RUN hmm.hmm_device_private.migrate_partial_unmap_fault ...
> > [ 14.589125] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
> > [ 14.589178] Modules linked in: test_hmm
> > [ 14.589203] CPU: 25 UID: 0 PID: 653 Comm: hmm-tests Not tainted 7.2.0-rc5+ #14 PREEMPT
> > [ 14.589243] Hardware name: linux,dummy-virt (DT)
> > [ 14.589268] pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> > [ 14.589300] pc : folio_unlock+0x78/0x88
> > [ 14.589326] lr : folio_unlock+0x78/0x88
> > [ 14.589349] sp : ffff80008284bb90
> > [ 14.589368] x29: ffff80008284bb90 x28: ffff0000cc8ce180 x27: 0000000000000000
> > [ 14.589406] x26: 0000000000000000 x25: ffff0000ca395dc0 x24: 0000000000000000
> > [ 14.589447] x23: 0000000020100073 x22: ffff0000c23d35c0 x21: ffffffffbfff8000
> > [ 14.589485] x20: ffffffffbfff8000 x19: ffff80008284bca0 x18: 0000000000000010
> > [ 14.589523] x17: 3030303030303030 x16: 2066666666666666 x15: 6630303030303030
> > [ 14.589562] x14: 0000000000000000 x13: 29296f696c6f6628 x12: 64656b636f6c5f74
> > [ 14.589603] x11: fffffffffffc7100 x10: fffffffffffc70b0 x9 : ffffb0504ff88f70
> > [ 14.589640] x8 : 3fffffffffffdfff x7 : ffff000c79b24bc0 x6 : 00000000000001a7
> > [ 14.589680] x5 : ffff000c79b24bc0 x4 : 0000000000000000 x3 : 0000000000000000
> > [ 14.589718] x2 : 0000000000000000 x1 : ffff0000cc8ce180 x0 : 000000000000003f
> > [ 14.589756] Call trace:
> > [ 14.589769] folio_unlock+0x78/0x88 (P)
> > [ 14.589792] do_swap_page+0xf40/0x1580
> > [ 14.589815] __handle_mm_fault+0x648/0xe68
> > [ 14.589838] handle_mm_fault+0x9c/0x330
> > [ 14.589858] do_page_fault+0x268/0x7e0
> > [ 14.589882] do_translation_fault+0x5c/0x80
> > [ 14.589904] do_mem_abort+0x48/0xa0
> > [ 14.589927] el0_da+0x38/0xd0
> > [ 14.589948] el0t_64_sync_handler+0xd0/0xe8
> > [ 14.589970] el0t_64_sync+0x198/0x1a0
> > [ 14.589990] Code: d65f03c0 d000eec1 913c4021 94015993 (d4210000)
> >
> > I can only speculate that we need another
> >
> > folio = page_folio(vmf->page);
> >
> > after the migrate_to_ram() call.
> >
> > Let me try that real quick.
> >
>
> Yeah, that fixes it:
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 4134ac607ee0..83d1a2be957c 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4937,6 +4937,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> pgmap = page_pgmap(vmf->page);
> ret = pgmap->ops->migrate_to_ram(vmf);
> + folio = page_folio(vmf->page);
So after migrate_to_ram() the folio might have been split or otherwise somehow
the page doesn't belong to the same locked, refcount-incremented folio it did
before?
That's kinda a footgun... but this documents it at least.
I think a comment explaining how this can happen would be helpful though as this
doesn't seem intuitive.
> folio_unlock(folio);
> folio_put(folio);
> } else {
>
>
> --
> Cheers,
>
> David
--
Cheers, Lorenzo
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2026-08-17 16:39 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-08-03 3:15 [PATCH v4] mm: Use a folio in the softleaf_is_device_private path Hongfu Li
2026-08-03 6:25 ` Anshuman Khandual
2026-08-17 15:52 ` David Hildenbrand (Arm)
2026-08-17 15:57 ` David Hildenbrand (Arm)
2026-08-17 16:39 ` Lorenzo Stoakes (ARM)
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