From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 603D523D281; Wed, 25 Mar 2026 09:47:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774432051; cv=none; b=Q6VVoyDu4oDBiezXkcjTmsJC/IEBsyyeFurc4qDAMK5fpvF+5WmfQhFKmI6K465hELUYjogonhMROIs/VtZblubQ5Jx50Xq1erb7eiEXIgyRBuL4Kr+QpNy0u9uyXVFfCkbPZcsJEU8kOknGx1qSNB+onzpXCYXLGAfDkmr2GO0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774432051; c=relaxed/simple; bh=vUFrcOFz84OveU1pgKHoD1qwpdPZX9ciji33h3siGaE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=aZnLNvsIizDm7i/tjj711gyDkHHekYIrWSYjBxt4p4odXKxXZX7PAroLFJnlMdA1PJKWxgwGZ8VoSPDoqTWBQ1LMJIywleZ0FcrU4MbQbcvCN5rIFRl9Rsw23gWvJ2ovMscSn0MjudMJMqJNhsYTKoeRMs2ZsOoJCl2P+W/HgtE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=h7rjxRys; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="h7rjxRys" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44F83C2BC9E; Wed, 25 Mar 2026 09:47:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774432051; bh=vUFrcOFz84OveU1pgKHoD1qwpdPZX9ciji33h3siGaE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=h7rjxRys800WY0i8LFUswSR3PcQtVI+WfcvFbM55iwz1ZH6sEQagzhf2LyOreVOSW R1lGyQTKbfLllWJzdn5W8eaoKRVYpL0edcGcr6SCeDfoN1NRmrSZOCLjsPkGst2Vue whTAV+F4IJb7xm4J+qcGoX5SFmIZFB+fhBwrR2605pUGNgx0fg/E3JSQRqS9sFkabZ CtbaFD/j2jHu/4k19QPOkOOINFcC55JlaP/BKzrZDZAQkiiAvQh9vim4ubQ9CkIKj9 xhp7ke2Xf5zs7lnOYxqAky/AVcczwO5PeQU9qs8vfUKFRe22DcZ0GFLqD7cqpncinF 7/z8KNyW3nyVA== Message-ID: <2bf17da7-fb46-4503-8de9-9368a73d8487@kernel.org> Date: Wed, 25 Mar 2026 10:47:21 +0100 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 10/21] fs: afs: restore mmap_prepare implementation Content-Language: en-US To: "Lorenzo Stoakes (Oracle)" , Andrew Morton Cc: Jonathan Corbet , Clemens Ladisch , Arnd Bergmann , Greg Kroah-Hartman , "K . Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Bodo Stroesser , "Martin K . Petersen" , David Howells , Marc Dionne , Alexander Viro , Christian Brauner , Jan Kara , David Hildenbrand , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-mtd@lists.infradead.org, linux-staging@lists.linux.dev, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ryan Roberts References: From: "Vlastimil Babka (SUSE)" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/20/26 23:39, Lorenzo Stoakes (Oracle) wrote: > Commit 9d5403b1036c ("fs: convert most other generic_file_*mmap() users to > .mmap_prepare()") updated AFS to use the mmap_prepare callback in favour > of the deprecated mmap callback. > > However, it did not account for the fact that mmap_prepare is called > pre-merge, and may then be merged, nor that mmap_prepare can fail to map > due to an out of memory error. > > This change was therefore since reverted. > > Both of those are cases in which we should not be incrementing a reference > count. > > With the newly added vm_ops->mapped callback available, we can simply > defer this operation to that callback which is only invoked once the > mapping is successfully in place (but not yet visible to userspace as the > mmap and VMA write locks are held). > > This allows us to once again reimplement the .mmap_prepare implementation > for this file system. > > Therefore add afs_mapped() to implement this callback for AFS, and remove > the code doing so in afs_mmap_prepare(). > > Also update afs_vm_open(), afs_vm_close() and afs_vm_map_pages() to be > consistent in how the vnode is accessed. > > Signed-off-by: Lorenzo Stoakes (Oracle) Yep that should take care of that reference count problem. Acked-by: Vlastimil Babka (SUSE) > --- > fs/afs/file.c | 42 +++++++++++++++++++++++++++++------------- > 1 file changed, 29 insertions(+), 13 deletions(-) > > diff --git a/fs/afs/file.c b/fs/afs/file.c > index 74d04af51ff4..85696ac984cc 100644 > --- a/fs/afs/file.c > +++ b/fs/afs/file.c > @@ -19,7 +19,7 @@ > #include > #include "internal.h" > > -static int afs_file_mmap(struct file *file, struct vm_area_struct *vma); > +static int afs_file_mmap_prepare(struct vm_area_desc *desc); > > static ssize_t afs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter); > static ssize_t afs_file_splice_read(struct file *in, loff_t *ppos, > @@ -28,6 +28,8 @@ static ssize_t afs_file_splice_read(struct file *in, loff_t *ppos, > static void afs_vm_open(struct vm_area_struct *area); > static void afs_vm_close(struct vm_area_struct *area); > static vm_fault_t afs_vm_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff); > +static int afs_mapped(unsigned long start, unsigned long end, pgoff_t pgoff, > + const struct file *file, void **vm_private_data); > > const struct file_operations afs_file_operations = { > .open = afs_open, > @@ -35,7 +37,7 @@ const struct file_operations afs_file_operations = { > .llseek = generic_file_llseek, > .read_iter = afs_file_read_iter, > .write_iter = netfs_file_write_iter, > - .mmap = afs_file_mmap, > + .mmap_prepare = afs_file_mmap_prepare, > .splice_read = afs_file_splice_read, > .splice_write = iter_file_splice_write, > .fsync = afs_fsync, > @@ -61,6 +63,7 @@ const struct address_space_operations afs_file_aops = { > }; > > static const struct vm_operations_struct afs_vm_ops = { > + .mapped = afs_mapped, > .open = afs_vm_open, > .close = afs_vm_close, > .fault = filemap_fault, > @@ -492,34 +495,47 @@ static void afs_drop_open_mmap(struct afs_vnode *vnode) > /* > * Handle setting up a memory mapping on an AFS file. > */ > -static int afs_file_mmap(struct file *file, struct vm_area_struct *vma) > +static int afs_file_mmap_prepare(struct vm_area_desc *desc) > { > - struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); > int ret; > > - afs_add_open_mmap(vnode); > + ret = generic_file_mmap_prepare(desc); > + if (ret) > + return ret; > > - ret = generic_file_mmap(file, vma); > - if (ret == 0) > - vma->vm_ops = &afs_vm_ops; > - else > - afs_drop_open_mmap(vnode); > + desc->vm_ops = &afs_vm_ops; > return ret; > } > > +static int afs_mapped(unsigned long start, unsigned long end, pgoff_t pgoff, > + const struct file *file, void **vm_private_data) > +{ > + struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); > + > + afs_add_open_mmap(vnode); > + return 0; > +} > + > static void afs_vm_open(struct vm_area_struct *vma) > { > - afs_add_open_mmap(AFS_FS_I(file_inode(vma->vm_file))); > + struct file *file = vma->vm_file; > + struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); > + > + afs_add_open_mmap(vnode); > } > > static void afs_vm_close(struct vm_area_struct *vma) > { > - afs_drop_open_mmap(AFS_FS_I(file_inode(vma->vm_file))); > + struct file *file = vma->vm_file; > + struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); > + > + afs_drop_open_mmap(vnode); > } > > static vm_fault_t afs_vm_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff) > { > - struct afs_vnode *vnode = AFS_FS_I(file_inode(vmf->vma->vm_file)); > + struct file *file = vmf->vma->vm_file; > + struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); > > if (afs_check_validity(vnode)) > return filemap_map_pages(vmf, start_pgoff, end_pgoff); > -- > 2.53.0