* [PATCH] mm/mapping_dirty_helpers: Update huge page-table entry callbacks
@ 2020-01-31 10:00 Thomas Hellström (VMware)
2020-01-31 11:33 ` Steven Price
0 siblings, 1 reply; 4+ messages in thread
From: Thomas Hellström (VMware) @ 2020-01-31 10:00 UTC (permalink / raw)
To: linux-mm, linux-kernel; +Cc: Thomas Hellstrom, Steven Price
From: Thomas Hellstrom <thellstrom@vmware.com>
Following the update of pagewalk code
commit a07984d48146 ("mm: pagewalk: add p4d_entry() and pgd_entry()")
we can modify the mapping_dirty_helpers' huge page-table entry callbacks
to avoid splitting when a huge pud or -pmd is encountered.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Steven Price <steven.price@arm.com>
---
mm/mapping_dirty_helpers.c | 42 ++++++++++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 4 deletions(-)
diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c
index 71070dda9643..2c7d03675903 100644
--- a/mm/mapping_dirty_helpers.c
+++ b/mm/mapping_dirty_helpers.c
@@ -111,26 +111,60 @@ static int clean_record_pte(pte_t *pte, unsigned long addr,
return 0;
}
-/* wp_clean_pmd_entry - The pagewalk pmd callback. */
+/*
+ * wp_clean_pmd_entry - The pagewalk pmd callback.
+ *
+ * Dirty-tracking should take place on the PTE level, so
+ * WARN() if encountering a dirty huge pmd.
+ * Furthermore, never split huge pmds, since that currently
+ * causes dirty info loss. The pagefault handler should do
+ * that if needed.
+ */
static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
- /* Dirty-tracking should be handled on the pte level */
pmd_t pmdval = pmd_read_atomic(pmd);
+ if (!pmd_trans_unstable(&pmdval))
+ return 0;
+
+ if (pmd_none(pmdval)) {
+ walk->action = ACTION_AGAIN;
+ return 0;
+ }
+
+ /* Huge pmd, present or migrated */
+ walk->action = ACTION_CONTINUE;
if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval))
WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval));
return 0;
}
-/* wp_clean_pud_entry - The pagewalk pud callback. */
+/*
+ * wp_clean_pud_entry - The pagewalk pud callback.
+ *
+ * Dirty-tracking should take place on the PTE level, so
+ * WARN() if encountering a dirty huge puds.
+ * Furthermore, never split huge puds, since that currently
+ * causes dirty info loss. The pagefault handler should do
+ * that if needed.
+ */
static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
- /* Dirty-tracking should be handled on the pte level */
pud_t pudval = READ_ONCE(*pud);
+ if (!pud_trans_unstable(&pudval))
+ return 0;
+
+ if (pud_none(pudval)) {
+ walk->action = ACTION_AGAIN;
+ return 0;
+ }
+
+ /* Huge pud */
+ walk->action = ACTION_CONTINUE;
if (pud_trans_huge(pudval) || pud_devmap(pudval))
WARN_ON(pud_write(pudval) || pud_dirty(pudval));
--
2.21.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] mm/mapping_dirty_helpers: Update huge page-table entry callbacks
2020-01-31 10:00 [PATCH] mm/mapping_dirty_helpers: Update huge page-table entry callbacks Thomas Hellström (VMware)
@ 2020-01-31 11:33 ` Steven Price
2020-01-31 14:55 ` Thomas Hellström (VMware)
0 siblings, 1 reply; 4+ messages in thread
From: Steven Price @ 2020-01-31 11:33 UTC (permalink / raw)
To: Thomas Hellström (VMware); +Cc: linux-mm, linux-kernel, Thomas Hellstrom
On Fri, Jan 31, 2020 at 10:00:52AM +0000, Thomas Hellström (VMware) wrote:
> From: Thomas Hellstrom <thellstrom@vmware.com>
>
> Following the update of pagewalk code
> commit a07984d48146 ("mm: pagewalk: add p4d_entry() and pgd_entry()")
> we can modify the mapping_dirty_helpers' huge page-table entry callbacks
> to avoid splitting when a huge pud or -pmd is encountered.
>
> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
> Cc: Steven Price <steven.price@arm.com>
LGTM
Reviewed-by: Steven Price <steven.price@arm.com>
> ---
> mm/mapping_dirty_helpers.c | 42 ++++++++++++++++++++++++++++++++++----
> 1 file changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c
> index 71070dda9643..2c7d03675903 100644
> --- a/mm/mapping_dirty_helpers.c
> +++ b/mm/mapping_dirty_helpers.c
> @@ -111,26 +111,60 @@ static int clean_record_pte(pte_t *pte, unsigned long addr,
> return 0;
> }
>
> -/* wp_clean_pmd_entry - The pagewalk pmd callback. */
> +/*
> + * wp_clean_pmd_entry - The pagewalk pmd callback.
> + *
> + * Dirty-tracking should take place on the PTE level, so
> + * WARN() if encountering a dirty huge pmd.
> + * Furthermore, never split huge pmds, since that currently
> + * causes dirty info loss. The pagefault handler should do
> + * that if needed.
> + */
> static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
> struct mm_walk *walk)
> {
> - /* Dirty-tracking should be handled on the pte level */
> pmd_t pmdval = pmd_read_atomic(pmd);
>
> + if (!pmd_trans_unstable(&pmdval))
> + return 0;
> +
> + if (pmd_none(pmdval)) {
> + walk->action = ACTION_AGAIN;
> + return 0;
> + }
> +
> + /* Huge pmd, present or migrated */
> + walk->action = ACTION_CONTINUE;
> if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval))
> WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval));
>
> return 0;
> }
>
> -/* wp_clean_pud_entry - The pagewalk pud callback. */
> +/*
> + * wp_clean_pud_entry - The pagewalk pud callback.
> + *
> + * Dirty-tracking should take place on the PTE level, so
> + * WARN() if encountering a dirty huge puds.
> + * Furthermore, never split huge puds, since that currently
> + * causes dirty info loss. The pagefault handler should do
> + * that if needed.
> + */
> static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
> struct mm_walk *walk)
> {
> - /* Dirty-tracking should be handled on the pte level */
> pud_t pudval = READ_ONCE(*pud);
>
> + if (!pud_trans_unstable(&pudval))
> + return 0;
> +
> + if (pud_none(pudval)) {
> + walk->action = ACTION_AGAIN;
> + return 0;
> + }
> +
> + /* Huge pud */
> + walk->action = ACTION_CONTINUE;
> if (pud_trans_huge(pudval) || pud_devmap(pudval))
> WARN_ON(pud_write(pudval) || pud_dirty(pudval));
>
> --
> 2.21.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm/mapping_dirty_helpers: Update huge page-table entry callbacks
2020-01-31 11:33 ` Steven Price
@ 2020-01-31 14:55 ` Thomas Hellström (VMware)
0 siblings, 0 replies; 4+ messages in thread
From: Thomas Hellström (VMware) @ 2020-01-31 14:55 UTC (permalink / raw)
To: Steven Price; +Cc: linux-mm, linux-kernel, Thomas Hellstrom
On 1/31/20 12:33 PM, Steven Price wrote:
> On Fri, Jan 31, 2020 at 10:00:52AM +0000, Thomas Hellström (VMware) wrote:
>> From: Thomas Hellstrom <thellstrom@vmware.com>
>>
>> Following the update of pagewalk code
>> commit a07984d48146 ("mm: pagewalk: add p4d_entry() and pgd_entry()")
>> we can modify the mapping_dirty_helpers' huge page-table entry callbacks
>> to avoid splitting when a huge pud or -pmd is encountered.
>>
>> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
>> Cc: Steven Price <steven.price@arm.com>
> LGTM
>
> Reviewed-by: Steven Price <steven.price@arm.com>
Thanks for reviewing, Steven!
/Thomas
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] mm/mapping_dirty_helpers: Update huge page-table entry callbacks
@ 2020-02-03 15:43 Thomas Hellström (VMware)
0 siblings, 0 replies; 4+ messages in thread
From: Thomas Hellström (VMware) @ 2020-02-03 15:43 UTC (permalink / raw)
To: linux-mm, linux-kernel; +Cc: Thomas Hellstrom, Andrew Morton, Steven Price
From: Thomas Hellstrom <thellstrom@vmware.com>
Following the update of pagewalk code
commit a07984d48146 ("mm: pagewalk: add p4d_entry() and pgd_entry()")
we can modify the mapping_dirty_helpers' huge page-table entry callbacks
to avoid splitting when a huge pud or -pmd is encountered.
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Steven Price <steven.price@arm.com>
---
v2: Added R-B from Steven.
---
mm/mapping_dirty_helpers.c | 42 ++++++++++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 4 deletions(-)
diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c
index 71070dda9643..2c7d03675903 100644
--- a/mm/mapping_dirty_helpers.c
+++ b/mm/mapping_dirty_helpers.c
@@ -111,26 +111,60 @@ static int clean_record_pte(pte_t *pte, unsigned long addr,
return 0;
}
-/* wp_clean_pmd_entry - The pagewalk pmd callback. */
+/*
+ * wp_clean_pmd_entry - The pagewalk pmd callback.
+ *
+ * Dirty-tracking should take place on the PTE level, so
+ * WARN() if encountering a dirty huge pmd.
+ * Furthermore, never split huge pmds, since that currently
+ * causes dirty info loss. The pagefault handler should do
+ * that if needed.
+ */
static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
- /* Dirty-tracking should be handled on the pte level */
pmd_t pmdval = pmd_read_atomic(pmd);
+ if (!pmd_trans_unstable(&pmdval))
+ return 0;
+
+ if (pmd_none(pmdval)) {
+ walk->action = ACTION_AGAIN;
+ return 0;
+ }
+
+ /* Huge pmd, present or migrated */
+ walk->action = ACTION_CONTINUE;
if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval))
WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval));
return 0;
}
-/* wp_clean_pud_entry - The pagewalk pud callback. */
+/*
+ * wp_clean_pud_entry - The pagewalk pud callback.
+ *
+ * Dirty-tracking should take place on the PTE level, so
+ * WARN() if encountering a dirty huge puds.
+ * Furthermore, never split huge puds, since that currently
+ * causes dirty info loss. The pagefault handler should do
+ * that if needed.
+ */
static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
- /* Dirty-tracking should be handled on the pte level */
pud_t pudval = READ_ONCE(*pud);
+ if (!pud_trans_unstable(&pudval))
+ return 0;
+
+ if (pud_none(pudval)) {
+ walk->action = ACTION_AGAIN;
+ return 0;
+ }
+
+ /* Huge pud */
+ walk->action = ACTION_CONTINUE;
if (pud_trans_huge(pudval) || pud_devmap(pudval))
WARN_ON(pud_write(pudval) || pud_dirty(pudval));
--
2.21.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2020-01-31 10:00 [PATCH] mm/mapping_dirty_helpers: Update huge page-table entry callbacks Thomas Hellström (VMware)
2020-01-31 11:33 ` Steven Price
2020-01-31 14:55 ` Thomas Hellström (VMware)
2020-02-03 15:43 Thomas Hellström (VMware)
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