From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4537ACCA470 for ; Tue, 7 Oct 2025 03:51:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 91BD18E000E; Mon, 6 Oct 2025 23:51:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8F2D68E000C; Mon, 6 Oct 2025 23:51:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 82F658E000E; Mon, 6 Oct 2025 23:51:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 7542B8E000C for ; Mon, 6 Oct 2025 23:51:30 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 0FE3F140145 for ; Tue, 7 Oct 2025 03:51:30 +0000 (UTC) X-FDA: 83969943540.08.643968D Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf14.hostedemail.com (Postfix) with ESMTP id EA98D100002 for ; Tue, 7 Oct 2025 03:51:27 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf14.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1759809088; h=from:from:sender: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=R5zytkwZkf6MqvQf3jDg+5VKMoKxrHNJ4a4qnATPueU=; b=q7Cd+fgg5eEkhO3Qtc++ibF0RbrLD/0+3tal3XTDqI2h+SWe7XiQT3l3QrZdk4nzqZvcYb PLOaWBwGwbC9TRqYHcUwaCsJrw0LXjDrvwIt+SWp3RgrCph5AxlKz4V+unHyvpcyhpfyZ5 FiRKFJ5VrwlSm4Fptezi3i4Yuuru0s4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1759809088; a=rsa-sha256; cv=none; b=N1Ic3swgfdyA64AS8nwEKZRj8HgdlR+wQt5NAmI9VBB4WNG3gh1pxLkzC//GxLwUDk5s1w 8+YKqHc4sfdKxVpSBcaT4eFBVgco+/8gjPUllA5sIoYqjPZz2ykM5TjW4qyqaVVMFdc8ce gNThsr+0G/FogYLWtk8cEXFHNALAjgQ= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf14.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CBEEA14BF; Mon, 6 Oct 2025 20:51:18 -0700 (PDT) Received: from [10.164.18.47] (unknown [10.164.18.47]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B9BD73F66E; Mon, 6 Oct 2025 20:51:23 -0700 (PDT) Message-ID: <2d753b43-58d7-4749-abd9-1d69c0ee5cf8@arm.com> Date: Tue, 7 Oct 2025 09:21:20 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm: Consistently use current->mm in mm_get_unmapped_area() To: Ryan Roberts , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20251003155306.2147572-1-ryan.roberts@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <20251003155306.2147572-1-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: EA98D100002 X-Rspamd-Server: rspam02 X-Stat-Signature: wshfyekwx5ojk85a3shq3tq7grrzjdwc X-HE-Tag: 1759809087-10268 X-HE-Meta: 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 9nQHEkHy tKQ0XLjVlWUCLoXJwMYPzs+CgUaa+kqdXNwvOpKrSEVfqQRdu4FK5G8TaayxXFyjrkO5hA+gWgNCqfhdGxFKsbSkfzF/5B8FnF4Ri0ld2AsdbGcP9jS4j2B4/vBQn5dz9FRgDvDF3r52binxH59UpB1DOUdhvyoGBJrtrlR7CdByCrc8fVGYL5C+IdW+fPBR+pJGpasgYfmSbQIVmO/gsEn8cM8khbHJY9LBaTm3zpMD+FFKOgZdICF40fw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/10/25 9:23 PM, Ryan Roberts wrote: > mm_get_unmapped_area() is a wrapper around arch_get_unmapped_area() / > arch_get_unmapped_area_topdown(), both of which search current->mm for > some free space. Neither take an mm_struct - they implicitly operate on > current->mm. > > But the wrapper takes an mm_struct and uses it to decide whether to > search bottom up or top down. All callers pass in current->mm for this, > so everything is working consistently. But it feels like an accident > waiting to happen; eventually someone will call that function with a > different mm, expecting to find free space in it, but what gets returned > is free space in the current mm. > > So let's simplify by removing the parameter and have the wrapper use > current->mm to decide which end to start at. Now everything is > consistent and self-documenting. > > Signed-off-by: Ryan Roberts > --- Reviewed-by: Anshuman Khandual > Applies against today's mm-unstable (aa05a436eca8). > > Build tested on arm64, x86 and Sparc. mm selftests show no regressions. > > Thanks, > Ryan > > arch/sparc/kernel/sys_sparc_64.c | 6 +++--- > arch/x86/kernel/cpu/sgx/driver.c | 2 +- > drivers/char/mem.c | 2 +- > drivers/dax/device.c | 5 ++--- > fs/hugetlbfs/inode.c | 3 +-- > fs/proc/inode.c | 2 +- > fs/ramfs/file-mmu.c | 2 +- > include/linux/sched/mm.h | 9 ++++----- > io_uring/memmap.c | 2 +- > kernel/bpf/arena.c | 2 +- > kernel/bpf/syscall.c | 2 +- > mm/huge_memory.c | 4 ++-- > mm/mmap.c | 17 +++++++---------- > mm/shmem.c | 8 +++----- > 14 files changed, 29 insertions(+), 37 deletions(-) > > diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c > index 55faf2effa46..dbf118b40601 100644 > --- a/arch/sparc/kernel/sys_sparc_64.c > +++ b/arch/sparc/kernel/sys_sparc_64.c > @@ -241,7 +241,7 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u > > if (flags & MAP_FIXED) { > /* Ok, don't mess with it. */ > - return mm_get_unmapped_area(current->mm, NULL, orig_addr, len, pgoff, flags); > + return mm_get_unmapped_area(NULL, orig_addr, len, pgoff, flags); > } > flags &= ~MAP_SHARED; > > @@ -254,7 +254,7 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u > align_goal = (64UL * 1024); > > do { > - addr = mm_get_unmapped_area(current->mm, NULL, orig_addr, > + addr = mm_get_unmapped_area(NULL, orig_addr, > len + (align_goal - PAGE_SIZE), pgoff, flags); > if (!(addr & ~PAGE_MASK)) { > addr = (addr + (align_goal - 1UL)) & ~(align_goal - 1UL); > @@ -273,7 +273,7 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u > * be obtained. > */ > if (addr & ~PAGE_MASK) > - addr = mm_get_unmapped_area(current->mm, NULL, orig_addr, len, pgoff, flags); > + addr = mm_get_unmapped_area(NULL, orig_addr, len, pgoff, flags); > > return addr; > } > diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c > index 7f8d1e11dbee..3b3efadb8cae 100644 > --- a/arch/x86/kernel/cpu/sgx/driver.c > +++ b/arch/x86/kernel/cpu/sgx/driver.c > @@ -113,7 +113,7 @@ static unsigned long sgx_get_unmapped_area(struct file *file, > if (flags & MAP_FIXED) > return addr; > > - return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); > + return mm_get_unmapped_area(file, addr, len, pgoff, flags); > } > > #ifdef CONFIG_COMPAT > diff --git a/drivers/char/mem.c b/drivers/char/mem.c > index 34b815901b20..db1ca53a6d01 100644 > --- a/drivers/char/mem.c > +++ b/drivers/char/mem.c > @@ -542,7 +542,7 @@ static unsigned long get_unmapped_area_zero(struct file *file, > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > return thp_get_unmapped_area(file, addr, len, pgoff, flags); > #else > - return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); > + return mm_get_unmapped_area(file, addr, len, pgoff, flags); > #endif > } > #endif /* CONFIG_MMU */ > diff --git a/drivers/dax/device.c b/drivers/dax/device.c > index 2bb40a6060af..7f1ed0db8337 100644 > --- a/drivers/dax/device.c > +++ b/drivers/dax/device.c > @@ -330,14 +330,13 @@ static unsigned long dax_get_unmapped_area(struct file *filp, > if ((off + len_align) < off) > goto out; > > - addr_align = mm_get_unmapped_area(current->mm, filp, addr, len_align, > - pgoff, flags); > + addr_align = mm_get_unmapped_area(filp, addr, len_align, pgoff, flags); > if (!IS_ERR_VALUE(addr_align)) { > addr_align += (off - addr_align) & (align - 1); > return addr_align; > } > out: > - return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags); > + return mm_get_unmapped_area(filp, addr, len, pgoff, flags); > } > > static const struct address_space_operations dev_dax_aops = { > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 9c94ed8c3ab0..7a39ac93495f 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -184,8 +184,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, > if (addr) > addr0 = ALIGN(addr, huge_page_size(h)); > > - return mm_get_unmapped_area_vmflags(current->mm, file, addr0, len, pgoff, > - flags, 0); > + return mm_get_unmapped_area_vmflags(file, addr0, len, pgoff, flags, 0); > } > > /* > diff --git a/fs/proc/inode.c b/fs/proc/inode.c > index 129490151be1..a1968821a55d 100644 > --- a/fs/proc/inode.c > +++ b/fs/proc/inode.c > @@ -443,7 +443,7 @@ pde_get_unmapped_area(struct proc_dir_entry *pde, struct file *file, unsigned lo > return pde->proc_ops->proc_get_unmapped_area(file, orig_addr, len, pgoff, flags); > > #ifdef CONFIG_MMU > - return mm_get_unmapped_area(current->mm, file, orig_addr, len, pgoff, flags); > + return mm_get_unmapped_area(file, orig_addr, len, pgoff, flags); > #endif > > return orig_addr; > diff --git a/fs/ramfs/file-mmu.c b/fs/ramfs/file-mmu.c > index b11f5b20b78b..c3ed1c5117b2 100644 > --- a/fs/ramfs/file-mmu.c > +++ b/fs/ramfs/file-mmu.c > @@ -35,7 +35,7 @@ static unsigned long ramfs_mmu_get_unmapped_area(struct file *file, > unsigned long addr, unsigned long len, unsigned long pgoff, > unsigned long flags) > { > - return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); > + return mm_get_unmapped_area(file, addr, len, pgoff, flags); > } > > const struct file_operations ramfs_file_operations = { > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index 0232d983b715..89274cb5daf3 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -189,12 +189,11 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, > unsigned long len, unsigned long pgoff, > unsigned long flags, vm_flags_t); > > -unsigned long mm_get_unmapped_area(struct mm_struct *mm, struct file *filp, > - unsigned long addr, unsigned long len, > - unsigned long pgoff, unsigned long flags); > +unsigned long mm_get_unmapped_area(struct file *filp, unsigned long addr, > + unsigned long len, unsigned long pgoff, > + unsigned long flags); > > -unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm, > - struct file *filp, > +unsigned long mm_get_unmapped_area_vmflags(struct file *filp, > unsigned long addr, > unsigned long len, > unsigned long pgoff, > diff --git a/io_uring/memmap.c b/io_uring/memmap.c > index 2e99dffddfc5..55984007eabf 100644 > --- a/io_uring/memmap.c > +++ b/io_uring/memmap.c > @@ -387,7 +387,7 @@ unsigned long io_uring_get_unmapped_area(struct file *filp, unsigned long addr, > #else > addr = 0UL; > #endif > - return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags); > + return mm_get_unmapped_area(filp, addr, len, pgoff, flags); > } > > #else /* !CONFIG_MMU */ > diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c > index 5b37753799d2..11f6543c4a07 100644 > --- a/kernel/bpf/arena.c > +++ b/kernel/bpf/arena.c > @@ -334,7 +334,7 @@ static unsigned long arena_get_unmapped_area(struct file *filp, unsigned long ad > return -EINVAL; > } > > - ret = mm_get_unmapped_area(current->mm, filp, addr, len * 2, 0, flags); > + ret = mm_get_unmapped_area(filp, addr, len * 2, 0, flags); > if (IS_ERR_VALUE(ret)) > return ret; > if ((ret >> 32) == ((ret + len - 1) >> 32)) > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 0fbfa8532c39..7afd94172765 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -1132,7 +1132,7 @@ static unsigned long bpf_get_unmapped_area(struct file *filp, unsigned long addr > if (map->ops->map_get_unmapped_area) > return map->ops->map_get_unmapped_area(filp, addr, len, pgoff, flags); > #ifdef CONFIG_MMU > - return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags); > + return mm_get_unmapped_area(filp, addr, len, pgoff, flags); > #else > return addr; > #endif > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 1b81680b4225..8b44f026a0b1 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1126,7 +1126,7 @@ static unsigned long __thp_get_unmapped_area(struct file *filp, > if (len_pad < len || (off + len_pad) < off) > return 0; > > - ret = mm_get_unmapped_area_vmflags(current->mm, filp, addr, len_pad, > + ret = mm_get_unmapped_area_vmflags(filp, addr, len_pad, > off >> PAGE_SHIFT, flags, vm_flags); > > /* > @@ -1163,7 +1163,7 @@ unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long add > if (ret) > return ret; > > - return mm_get_unmapped_area_vmflags(current->mm, filp, addr, len, pgoff, flags, > + return mm_get_unmapped_area_vmflags(filp, addr, len, pgoff, flags, > vm_flags); > } > > diff --git a/mm/mmap.c b/mm/mmap.c > index 5fd3b80fda1d..644f02071a41 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -797,12 +797,11 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, > } > #endif > > -unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm, struct file *filp, > - unsigned long addr, unsigned long len, > - unsigned long pgoff, unsigned long flags, > - vm_flags_t vm_flags) > +unsigned long mm_get_unmapped_area_vmflags(struct file *filp, unsigned long addr, > + unsigned long len, unsigned long pgoff, > + unsigned long flags, vm_flags_t vm_flags) > { > - if (mm_flags_test(MMF_TOPDOWN, mm)) > + if (mm_flags_test(MMF_TOPDOWN, current->mm)) > return arch_get_unmapped_area_topdown(filp, addr, len, pgoff, > flags, vm_flags); > return arch_get_unmapped_area(filp, addr, len, pgoff, flags, vm_flags); > @@ -848,7 +847,7 @@ __get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, > addr = thp_get_unmapped_area_vmflags(file, addr, len, > pgoff, flags, vm_flags); > } else { > - addr = mm_get_unmapped_area_vmflags(current->mm, file, addr, len, > + addr = mm_get_unmapped_area_vmflags(file, addr, len, > pgoff, flags, vm_flags); > } > if (IS_ERR_VALUE(addr)) > @@ -864,12 +863,10 @@ __get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, > } > > unsigned long > -mm_get_unmapped_area(struct mm_struct *mm, struct file *file, > - unsigned long addr, unsigned long len, > +mm_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, > unsigned long pgoff, unsigned long flags) > { > - return mm_get_unmapped_area_vmflags(mm, file, addr, len, > - pgoff, flags, 0); > + return mm_get_unmapped_area_vmflags(file, addr, len, pgoff, flags, 0); > } > EXPORT_SYMBOL(mm_get_unmapped_area); > > diff --git a/mm/shmem.c b/mm/shmem.c > index 7db01567b645..354ea20384fa 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2756,8 +2756,7 @@ unsigned long shmem_get_unmapped_area(struct file *file, > if (len > TASK_SIZE) > return -ENOMEM; > > - addr = mm_get_unmapped_area(current->mm, file, uaddr, len, pgoff, > - flags); > + addr = mm_get_unmapped_area(file, uaddr, len, pgoff, flags); > > if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > return addr; > @@ -2835,8 +2834,7 @@ unsigned long shmem_get_unmapped_area(struct file *file, > if (inflated_len < len) > return addr; > > - inflated_addr = mm_get_unmapped_area(current->mm, NULL, uaddr, > - inflated_len, 0, flags); > + inflated_addr = mm_get_unmapped_area(NULL, uaddr, inflated_len, 0, flags); > if (IS_ERR_VALUE(inflated_addr)) > return addr; > if (inflated_addr & ~PAGE_MASK) > @@ -5772,7 +5770,7 @@ unsigned long shmem_get_unmapped_area(struct file *file, > unsigned long addr, unsigned long len, > unsigned long pgoff, unsigned long flags) > { > - return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); > + return mm_get_unmapped_area(file, addr, len, pgoff, flags); > } > #endif > > -- > 2.43.0 > >