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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan , Randy Dunlap , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Zhen Ni Subject: [PATCH v2 1/8] mm/page_owner: Add PID filtering support Date: Thu, 3 Sep 2026 12:18:12 +0800 Message-Id: <20260903041819.1776630-2-zhen.ni@easystack.cn> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20260903041819.1776630-1-zhen.ni@easystack.cn> References: <20260903041819.1776630-1-zhen.ni@easystack.cn> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-HM-Tid: 0aa0657d642c0229kunm7336907a330a0 X-HM-MType: 1 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFJQjdXWRgWCB1ZQUpXWS1ZQUlXWQ8JGhUIEh9ZQVkaSU1IVkgZSRpNSEMYSEIYTFYVFA kWGhdVGRETFhoSFyQUDg9ZV1kYEgtZQVlJSkNVQk9VSkpDVUJLWVdZFhoPEhUdFFlBWU9LSFVKS0 lPT09IVUpLS1VKQktLWQY+ Add PID filtering support. Users can filter page_owner output by process IDs using the "pid=" command format. The filter supports up to 16 PIDs specified as a comma-separated list. PIDs are stored in sorted order for efficient binary search matching during page owner iteration. Signed-off-by: Zhen Ni --- Changes in v2: - Drop the kstrdup() copy in parse_pid_t_list(); parse the token in place. This also fixes a leak on success and a kfree() of an advanced pointer on error in v1. - Use cmp_int() in cmp_pid_t() to avoid overflow on subtraction. - Reject pids exceeding PID_MAX_LIMIT. v1: https://lore.kernel.org/linux-mm/20260828031339.1270699-2-zhen.ni@easystack.cn/ --- mm/page_owner.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 73 insertions(+), 2 deletions(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index fbbda7ba914b..0ef081e443f9 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -12,6 +12,8 @@ #include #include #include +#include +#include #include "page_alloc.h" @@ -66,12 +68,24 @@ static const char * const page_owner_print_mode_strings[] = { [PAGE_OWNER_PRINT_STACK_HANDLE] = "stack_handle", }; +/* PID_MAX_LIMIT = 4,194,304 (7 decimal digits) */ +#define PID_MAX_DIGITS 7 +#define MAX_FILTER_PIDS 16 + struct page_owner_filter_state { enum page_owner_print_mode print_mode; - nodemask_t nid_filter; bool nid_filter_enabled; + bool proc_filter_enabled; + nodemask_t nid_filter; + int pid_count; + pid_t pid_list[MAX_FILTER_PIDS]; }; +static int cmp_pid_t(const void *a, const void *b) +{ + return cmp_int(*(pid_t *)a, *(pid_t *)b); +} + static bool page_owner_enabled __initdata; DEFINE_STATIC_KEY_FALSE(page_owner_inited); @@ -820,6 +834,19 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) goto ext_put_continue; } + if (state->proc_filter_enabled) { + bool proc_match = false; + + proc_match = bsearch(&page_owner->pid, + state->pid_list, + state->pid_count, + sizeof(pid_t), + cmp_pid_t) != NULL; + + if (!proc_match) + goto ext_put_continue; + } + /* Record the next PFN to read in the file offset */ *ppos = pfn + 1; @@ -927,6 +954,7 @@ static int page_owner_open(struct inode *inode, struct file *file) state->print_mode = PAGE_OWNER_PRINT_STACK; nodes_clear(state->nid_filter); state->nid_filter_enabled = false; + state->proc_filter_enabled = false; file->private_data = state; return 0; } @@ -937,6 +965,27 @@ static int page_owner_release(struct inode *inode, struct file *file) return 0; } +static int parse_pid_t_list(char *str, pid_t *list, int *count) +{ + char *token; + int i = 0; + + while ((token = strsep(&str, ",")) != NULL) { + unsigned int pid; + + if (*token == '\0') + continue; + if (i >= MAX_FILTER_PIDS) + return -E2BIG; + if (kstrtouint(token, 10, &pid) != 0 || pid > PID_MAX_LIMIT) + return -EINVAL; + list[i++] = (pid_t)pid; + } + + *count = i; + return 0; +} + static ssize_t page_owner_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) @@ -949,6 +998,9 @@ static ssize_t page_owner_write(struct file *file, enum page_owner_print_mode new_print_mode; nodemask_t new_nid_filter; bool new_nid_filter_enabled; + bool new_proc_filter_enabled; + pid_t new_pid_list[MAX_FILTER_PIDS]; + int new_pid_count = 0; /* * Maximum input length for filter commands: @@ -956,8 +1008,10 @@ static ssize_t page_owner_write(struct file *file, * with sufficient buffer * - 6 * MAX_NUMNODES: worst case for nid list * Worst case per node: ",NNNNN" (comma + 5-digit node number) = 6 bytes + * - For list filters: (digit+comma) * count + prefix */ - if (count > 32 + 6 * MAX_NUMNODES) + if (count > 32 + 6 * MAX_NUMNODES + + (PID_MAX_DIGITS + 1) * MAX_FILTER_PIDS + 4) return -EINVAL; kbuf = memdup_user_nul(buf, count); @@ -969,6 +1023,11 @@ static ssize_t page_owner_write(struct file *file, new_print_mode = state->print_mode; new_nid_filter = state->nid_filter; new_nid_filter_enabled = state->nid_filter_enabled; + new_proc_filter_enabled = state->proc_filter_enabled; + if (state->pid_count > 0) { + memcpy(new_pid_list, state->pid_list, sizeof(state->pid_list)); + new_pid_count = state->pid_count; + } while ((token = strsep(&kbuf, " \t\n")) != NULL) { if (*token == '\0') @@ -1000,6 +1059,10 @@ static ssize_t page_owner_write(struct file *file, } new_nid_filter_enabled = true; + } else if (!strncmp(token, "pid=", 4)) { + ret = parse_pid_t_list(token + 4, new_pid_list, &new_pid_count); + if (ret < 0) + goto out_free; } else { ret = -EINVAL; goto out_free; @@ -1010,6 +1073,14 @@ static ssize_t page_owner_write(struct file *file, state->print_mode = new_print_mode; state->nid_filter = new_nid_filter; state->nid_filter_enabled = new_nid_filter_enabled; + state->proc_filter_enabled = new_pid_count > 0; + if (new_pid_count > 0) { + memcpy(state->pid_list, new_pid_list, sizeof(state->pid_list)); + state->pid_count = new_pid_count; + } + if (state->pid_count > 1) + sort(state->pid_list, state->pid_count, sizeof(pid_t), + cmp_pid_t, NULL); ret = count; -- 2.20.1