From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6296329408 for ; Thu, 14 May 2026 04:38:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778733519; cv=none; b=C7OqHOBItjJwMhESQVQtcy/nBetBx/jHpAxl1jJEhcNz+j6RLL7PWFR3vgacSF9sqDcEznKf6pkyYuWF3j+2dunTgYvU9lto7sKIPA7pza0cGu6C6YuEYZqo1XqnGJAwlYZQT4xLmdMRy1FOBmM0oBYXzEK1pFWSpl32kE5x4g8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778733519; c=relaxed/simple; bh=L/lSeF7WmUf28X+CMiGVZtGvuWoEUcJdiav40dNIjKY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Xy4FoxAkQnKBwHMq2XWwdLRaOZ6QmRBWHbOxCYzc8I3Zo5Y9yZQBOEawAKCjl3F6J1GcPZEzBs/Cvmu55AoNxvoPc1tvI1OEtbs2ky+mi3Tph41M5zgQHGir22JLEIcF3gWf0I1cKRQvTQIa90gu4lbJTctFH/t6/jbVHBFcfts= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=bokvcCsF; arc=none smtp.client-ip=95.215.58.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="bokvcCsF" Message-ID: <2f546525-8ff6-4bbe-86ae-6f474f7cefe3@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1778733513; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EWNhhBT8Z0IhLnSUQk0yXuRYGsrjvO9GHYLlwg3Do9Q=; b=bokvcCsFWi+j1ORUOuyiXHXuYUcjMDLXSW7ByB4SLr6jV08jf4ZYZSM4/QHEKpwWKaobkH w32++mQEH9AkoorDLbhgHrkjsxmRAIsURlswJXp460Eux8M32nlV/2mpqNNMCmJ5oOy5iP HgzntiGnP44bFbnUvaUInZS/oVDRgGM= Date: Thu, 14 May 2026 12:37:42 +0800 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH 1/6] alloc_tag: add ioctl to /proc/allocinfo To: Suren Baghdasaryan Cc: Shuah Khan , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sourav Panda , Abhishek Bapat , Kent Overstreet , Andrew Morton References: Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Hao Ge In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Hi Suren and Abhishek Thanks for the patch! A couple of minor comments below. On 2026/5/5 07:36, Abhishek Bapat wrote: > From: Suren Baghdasaryan > > Add the following ioctl commands for /proc/allocinfo file: > > ALLOCINFO_IOC_CONTENT_ID - gets content identifier which can be used > to check whether the file content has changed specifically due to module > load/unload. Every time a module is loaded / unloaded, the returned > value will be different. By comparing the identifier value at the > beginning and at the end of the content retrieval operation, users can > validate retrieved information for consistency. > > ALLOCINFO_IOC_GET_AT - gets the record at the specified position. This > is the position of a record in /proc/allocinfo. > > ALLOCINFO_IOC_GET_NEXT - gets the record next to the last retrieved > one. If no records were previously retrieved, returns the first > record. > > Signed-off-by: Suren Baghdasaryan > Signed-off-by: Abhishek Bapat > --- > .../userspace-api/ioctl/ioctl-number.rst | 2 + > include/linux/codetag.h | 1 + > include/uapi/linux/alloc_tag.h | 54 ++++++ > lib/alloc_tag.c | 178 +++++++++++++++++- > lib/codetag.c | 11 ++ > 5 files changed, 244 insertions(+), 2 deletions(-) > create mode 100644 include/uapi/linux/alloc_tag.h > > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst > index 331223761fff..84f6808a8578 100644 > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst > @@ -349,6 +349,8 @@ Code Seq# Include File Comments > > 0xA5 20-2F linux/surface_aggregator/dtx.h Microsoft Surface DTX driver > > +0xA6 00-0F uapi/linux/alloc_tag.h Memory allocation profiling > + > 0xAA 00-3F linux/uapi/linux/userfaultfd.h > 0xAB 00-1F linux/nbd.h > 0xAC 00-1F linux/raw.h > diff --git a/include/linux/codetag.h b/include/linux/codetag.h > index 8ea2a5f7c98a..2bcd4e7c809e 100644 > --- a/include/linux/codetag.h > +++ b/include/linux/codetag.h > @@ -76,6 +76,7 @@ struct codetag_iterator { > > void codetag_lock_module_list(struct codetag_type *cttype, bool lock); > bool codetag_trylock_module_list(struct codetag_type *cttype); > +unsigned long codetag_get_content_id(struct codetag_type *cttype); > struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype); > struct codetag *codetag_next_ct(struct codetag_iterator *iter); > > diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h > new file mode 100644 > index 000000000000..e9a5b55fcc7a > --- /dev/null > +++ b/include/uapi/linux/alloc_tag.h > @@ -0,0 +1,54 @@ > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ > +/* > + * include/linux/alloc_tag.h > + */ > + > +#ifndef _UAPI_ALLOC_TAG_H > +#define _UAPI_ALLOC_TAG_H > + > +#include > + > +#define ALLOCINFO_STR_SIZE 64 > + > +struct allocinfo_content_id { > + __u64 id; > +}; > + > +struct allocinfo_tag { > + /* Longer names are trimmed */ > + char modname[ALLOCINFO_STR_SIZE]; > + char function[ALLOCINFO_STR_SIZE]; > + char filename[ALLOCINFO_STR_SIZE]; > + __u64 lineno; > +}; > + > +struct allocinfo_counter { > + __u64 bytes; > + __u64 calls; > + __u8 accurate; > + __u8 pad[7]; /* Add alignment to not break the 32-bit compatible interface */ > +}; > + > +struct allocinfo_tag_data { > + struct allocinfo_tag tag; > + struct allocinfo_counter counter; > +}; > + > +struct allocinfo_get_at { > + __u64 pos; /* input */ > + struct allocinfo_tag_data data; > +}; > + > +#define _ALLOCINFO_IOC_CONTENT_ID 0 > +#define _ALLOCINFO_IOC_GET_AT 1 > +#define _ALLOCINFO_IOC_GET_NEXT 2 > + > +#define ALLOCINFO_IOC_BASE 0xA6 > +#define ALLOCINFO_IOC_CONTENT_ID _IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_CONTENT_ID, \ > + struct allocinfo_content_id) > +#define ALLOCINFO_IOC_GET_AT _IOWR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_AT, \ > + struct allocinfo_get_at) > +#define ALLOCINFO_IOC_GET_NEXT _IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_NEXT, \ > + struct allocinfo_tag_data) > + > +#endif /* _UAPI_ALLOC_TAG_H */ > diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c > index ed1bdcf1f8ab..5c24d2f954d4 100644 > --- a/lib/alloc_tag.c > +++ b/lib/alloc_tag.c > @@ -14,6 +14,7 @@ > #include > #include > #include > +#include > > #define ALLOCINFO_FILE_NAME "allocinfo" > #define MODULE_ALLOC_TAG_VMAP_SIZE (100000UL * sizeof(struct alloc_tag)) > @@ -46,6 +47,9 @@ int alloc_tag_ref_offs; > struct allocinfo_private { > struct codetag_iterator iter; > bool print_header; > + /* ioctl uses a separate iterator not to interfere with reads */ > + struct codetag_iterator ioctl_iter; > + bool positioned; /* seq_open_private() sets to 0 */ > }; > > static void *allocinfo_start(struct seq_file *m, loff_t *pos) > @@ -125,6 +129,177 @@ static const struct seq_operations allocinfo_seq_op = { > .show = allocinfo_show, > }; > > +static int allocinfo_open(struct inode *inode, struct file *file) > +{ > + return seq_open_private(file, &allocinfo_seq_op, > + sizeof(struct allocinfo_private)); > +} > + > +static int allocinfo_release(struct inode *inode, struct file *file) > +{ > + return seq_release_private(inode, file); > +} > + > +static const char *allocinfo_str(const char *str) > +{ > + size_t len = strlen(str); > + > + /* Keep an extra space for the trailing NULL. */ > + if (len >= ALLOCINFO_STR_SIZE) > + str += (len - ALLOCINFO_STR_SIZE) + 1; > + return str; > +} > + > +/* Copy a string and trim from the beginning if it's too long */ > +static void allocinfo_copy_str(char *dest, const char *src) > +{ > + strscpy(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE); > +} > + > +static void allocinfo_to_params(struct codetag *ct, > + struct allocinfo_tag_data *data) > +{ > + struct alloc_tag *tag = ct_to_alloc_tag(ct); > + struct alloc_tag_counters counter = alloc_tag_read(tag); > + > + if (ct->modname) > + allocinfo_copy_str(data->tag.modname, ct->modname); > + else > + data->tag.modname[0] = '\0'; Minor nit about allocinfo_to_params(): When modname is NULL (built-in kernel code), the current code sets it to an empty string:     if (ct->modname)         allocinfo_copy_str(data->tag.modname, ct->modname);     else         data->tag.modname[0] = '\0'; This is of course workable in userspace by checking for an empty string, but I was wondering if it would be cleaner to use "vmlinux" as a default: else           allocinfo_copy_str(data->tag.modname, "vmlinux"); For some context, in our memory analysis workflow we often group allocations by module to get a quick overview of where memory goes, for example: vmlinux:    2.1 GB    (kernel core) nvidia:     1.2 GB    (GPU driver) iwlwifi:    800 MB    (WiFi driver) ext4:       500 MB    (filesystem) Having a consistent identifier for kernel built-in allocations would avoid each userspace tool needing to handle the empty string as a special case. Totally fine if this is intentional though. > + allocinfo_copy_str(data->tag.function, ct->function); > + allocinfo_copy_str(data->tag.filename, ct->filename); > + data->tag.lineno = ct->lineno; > + data->counter.bytes = counter.bytes; > + data->counter.calls = counter.calls; > + data->counter.accurate = !alloc_tag_is_inaccurate(tag); > +} > + > +static int allocinfo_ioctl_get_content_id(struct seq_file *m, void __user *arg) > +{ > + struct allocinfo_content_id params; > + > + codetag_lock_module_list(alloc_tag_cttype, true); > + params.id = codetag_get_content_id(alloc_tag_cttype); > + codetag_lock_module_list(alloc_tag_cttype, false); > + if (copy_to_user(arg, ¶ms, sizeof(params))) > + return -EFAULT; > + > + return 0; > +} > + > +static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg) > +{ > + struct allocinfo_private *priv; > + struct codetag *ct; > + __u64 pos; > + struct allocinfo_get_at params = {0}; > + > + if (copy_from_user(¶ms, arg, sizeof(params))) > + return -EFAULT; > + > + priv = (struct allocinfo_private *)m->private; > + pos = params.pos; > + > + codetag_lock_module_list(alloc_tag_cttype, true); > + > + /* Find the codetag */ > + priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype); > + ct = codetag_next_ct(&priv->ioctl_iter); > + while (ct && pos--) > + ct = codetag_next_ct(&priv->ioctl_iter); I noticed that codetag_next_ct(&priv->ioctl_iter) and priv->positioned are accessed without serialization in the ioctl path. Concurrent ioctl calls on the same fd could race on these fields. Just something I spotted while reading the code. Thanks Best Regards Hao > + if (ct) { > + allocinfo_to_params(ct, ¶ms.data); > + priv->positioned = true; > + } > + > + codetag_lock_module_list(alloc_tag_cttype, false); > + > + if (!ct) > + return -ENOENT; > + > + if (copy_to_user(arg, ¶ms, sizeof(params))) > + return -EFAULT; > + > + return 0; > +} > + > +static int allocinfo_ioctl_get_next(struct seq_file *m, void __user *arg) > +{ > + struct allocinfo_private *priv; > + struct codetag *ct; > + struct allocinfo_tag_data params = {0}; > + int ret = 0; > + > + priv = (struct allocinfo_private *)m->private; > + > + codetag_lock_module_list(alloc_tag_cttype, true); > + > + if (!priv->positioned) { > + priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype); > + priv->positioned = true; > + } > + > + ct = codetag_next_ct(&priv->ioctl_iter); > + if (ct) > + allocinfo_to_params(ct, ¶ms); > + > + if (!ct) { > + priv->positioned = false; > + ret = -ENOENT; > + } > + codetag_lock_module_list(alloc_tag_cttype, false); > + > + if (ret == 0) { > + if (copy_to_user(arg, ¶ms, sizeof(params))) > + return -EFAULT; > + } > + return ret; > +} > + > +static long allocinfo_ioctl(struct file *file, unsigned int cmd, > + unsigned long __arg) > +{ > + void __user *arg = (void __user *)__arg; > + int ret; > + > + switch (cmd) { > + case ALLOCINFO_IOC_CONTENT_ID: > + ret = allocinfo_ioctl_get_content_id(file->private_data, arg); > + break; > + case ALLOCINFO_IOC_GET_AT: > + ret = allocinfo_ioctl_get_at(file->private_data, arg); > + break; > + case ALLOCINFO_IOC_GET_NEXT: > + ret = allocinfo_ioctl_get_next(file->private_data, arg); > + break; > + default: > + ret = -ENOIOCTLCMD; > + break; > + } > + > + return ret; > +} > + > +#ifdef CONFIG_COMPAT > +static long allocinfo_compat_ioctl(struct file *file, unsigned int cmd, > + unsigned long arg) > +{ > + return allocinfo_ioctl(file, cmd, (unsigned long)compat_ptr(arg)); > +} > +#endif > + > +static const struct proc_ops allocinfo_proc_ops = { > + .proc_open = allocinfo_open, > + .proc_read_iter = seq_read_iter, > + .proc_lseek = seq_lseek, > + .proc_release = allocinfo_release, > + .proc_ioctl = allocinfo_ioctl, > +#ifdef CONFIG_COMPAT > + .proc_compat_ioctl = allocinfo_compat_ioctl, > +#endif > + > +}; > + > size_t alloc_tag_top_users(struct codetag_bytes *tags, size_t count, bool can_sleep) > { > struct codetag_iterator iter; > @@ -946,8 +1121,7 @@ static int __init alloc_tag_init(void) > return 0; > } > > - if (!proc_create_seq_private(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_seq_op, > - sizeof(struct allocinfo_private), NULL)) { > + if (!proc_create(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_proc_ops)) { > pr_err("Failed to create %s file\n", ALLOCINFO_FILE_NAME); > shutdown_mem_profiling(false); > return -ENOMEM; > diff --git a/lib/codetag.c b/lib/codetag.c > index 304667897ad4..93aa30991563 100644 > --- a/lib/codetag.c > +++ b/lib/codetag.c > @@ -48,6 +48,17 @@ bool codetag_trylock_module_list(struct codetag_type *cttype) > return down_read_trylock(&cttype->mod_lock) != 0; > } > > +unsigned long codetag_get_content_id(struct codetag_type *cttype) > +{ > + lockdep_assert_held(&cttype->mod_lock); > + > + /* > + * next_mod_seq is updated on every load, so can be used to identify > + * content changes. > + */ > + return cttype->next_mod_seq; > +} > + > struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype) > { > struct codetag_iterator iter = {