Re: [PATCH v5] mm/page_owner.c: add llseek for page_owner
From: Vlastimil Babka
Date: Wed Aug 10 2022 - 05:03:03 EST
On 8/10/22 03:33, Kassey Li wrote:
On 8/9/2022 5:30 PM, Vlastimil Babka (SUSE) wrote:
On 8/9/22 04:47, Kassey Li wrote:
There is usage to dump a given cma region page_owner
instead of all page's.
This change allows to specify a ppos as start_pfn
by fseek.
Any invalid ppos will be skipped, so it did not
broken the origin dump feature.
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Kassey Li <quic_yingangl@xxxxxxxxxxx>
---
Documentation/vm/page_owner.rst | 6 ++++++
mm/internal.h | 5 +++++
mm/page_owner.c | 9 ++++++---
3 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/Documentation/vm/page_owner.rst b/Documentation/vm/page_owner.rst
index f5c954afe97c..8d33d976da8a 100644
--- a/Documentation/vm/page_owner.rst
+++ b/Documentation/vm/page_owner.rst
@@ -95,6 +95,12 @@ Usage
PFN XXX ...
// Detailed stack
+ By default, it will do full pfn dump, to start with a given pfn,
+ page_owner supports fseek.
+
+ FILE *fp = fopen("/sys/kernel/debug/page_owner", "r");
+ fseek(fp, pfn_start, SEEK_SET);
+
The ``page_owner_sort`` tool ignores ``PFN`` rows, puts the remaining rows
in buf, uses regexp to extract the page order value, counts the times
and pages of buf, and finally sorts them according to the parameter(s).
diff --git a/mm/internal.h b/mm/internal.h
index c0f8fbe0445b..1ad8f86e6e33 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -189,6 +189,11 @@ extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason
*/
extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
+/*
+ * in mm/page_owner.c:
This should say where it's defined, not used from, and that's
fs/proc/base.c. But it's already declared in fs/proc/internal.h so maybe
page_owner.c could just include that header (although it's a bit meh).
ok, let's do it.
Sorry, my suggestion was wrong as the kernel test bot just showed us.
mem_lseek() may be unavailable without CONFIG_PROC_FS.
The easiest way is you add a page_owner specific one back, but make it
correct for SEEK_CUR. Thanks.
+ */
+extern loff_t mem_lseek(struct file *, loff_t, int);
+
/*
* in mm/page_alloc.c
*/
diff --git a/mm/page_owner.c b/mm/page_owner.c
index e4c6f3f1695b..dcbe05e206e1 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -497,8 +497,10 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
return -EINVAL;
page = NULL;
- pfn = min_low_pfn + *ppos;
-
+ if (*ppos == 0)
+ pfn= min_low_pfn;
missing space before '='
my bad, for v6
./scripts/checkpatch.pl
v6-0001-mm-page_owner.c-add-llseek-for-page_owner.patch
total: 0 errors, 0 warnings, 46 lines checked
v6-0001-mm-page_owner.c-add-llseek-for-page_owner.patch has no obvious
style problems and is ready for submission.
+ else
+ pfn = *ppos;
/* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
pfn++;
@@ -561,7 +563,7 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
continue;
/* Record the next PFN to read in the file offset */
- *ppos = (pfn - min_low_pfn) + 1;
+ *ppos = pfn + 1;
return print_page_owner(buf, count, pfn, page,
page_owner, handle);
@@ -660,6 +662,7 @@ static void init_early_allocated_pages(void)
static const struct file_operations proc_page_owner_operations = {
.read = read_page_owner,
+ .llseek = mem_lseek,
};
static int __init pageowner_init(void)