Message-ID: <ukr7xbwqqqtlqqjq6hzmzketl7skwhfkrvu2yhueaekjlegqx6@amlqsqgbjix4>
Date: Tue, 17 Jun 2025 12:11:03 +0200
From: Jan Kara <jack@...e.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R . Howlett" <Liam.Howlett@...cle.com>, Jens Axboe <axboe@...nel.dk>, 
	Jani Nikula <jani.nikula@...ux.intel.com>, Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, 
	Rodrigo Vivi <rodrigo.vivi@...el.com>, Tvrtko Ursulin <tursulin@...ulin.net>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Eric Van Hensbergen <ericvh@...nel.org>, Latchesar Ionkov <lucho@...kov.net>, 
	Dominique Martinet <asmadeus@...ewreck.org>, Christian Schoenebeck <linux_oss@...debyte.com>, 
	David Sterba <dsterba@...e.com>, David Howells <dhowells@...hat.com>, 
	Marc Dionne <marc.dionne@...istor.com>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, Benjamin LaHaise <bcrl@...ck.org>, 
	Miklos Szeredi <miklos@...redi.hu>, Amir Goldstein <amir73il@...il.com>, 
	Kent Overstreet <kent.overstreet@...ux.dev>, "Tigran A . Aivazian" <aivazian.tigran@...il.com>, 
	Kees Cook <kees@...nel.org>, Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>, 
	Xiubo Li <xiubli@...hat.com>, Ilya Dryomov <idryomov@...il.com>, 
	Jan Harkes <jaharkes@...cmu.edu>, coda@...cmu.edu, Tyler Hicks <code@...icks.com>, 
	Gao Xiang <xiang@...nel.org>, Chao Yu <chao@...nel.org>, Yue Hu <zbestahu@...il.com>, 
	Jeffle Xu <jefflexu@...ux.alibaba.com>, Sandeep Dhavale <dhavale@...gle.com>, 
	Hongbo Li <lihongbo22@...wei.com>, Namjae Jeon <linkinjeon@...nel.org>, 
	Sungjong Seo <sj1557.seo@...sung.com>, Yuezhang Mo <yuezhang.mo@...y.com>, 
	Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, 
	Jaegeuk Kim <jaegeuk@...nel.org>, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>, 
	Viacheslav Dubeyko <slava@...eyko.com>, John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, 
	Yangtao Li <frank.li@...o.com>, Richard Weinberger <richard@....at>, 
	Anton Ivanov <anton.ivanov@...bridgegreys.com>, Johannes Berg <johannes@...solutions.net>, 
	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>, David Woodhouse <dwmw2@...radead.org>, 
	Dave Kleikamp <shaggy@...nel.org>, Trond Myklebust <trondmy@...nel.org>, 
	Anna Schumaker <anna@...nel.org>, Ryusuke Konishi <konishi.ryusuke@...il.com>, 
	Konstantin Komarov <almaz.alexandrovich@...agon-software.com>, Mark Fasheh <mark@...heh.com>, Joel Becker <jlbec@...lplan.org>, 
	Joseph Qi <joseph.qi@...ux.alibaba.com>, Bob Copeland <me@...copeland.com>, 
	Mike Marshall <hubcap@...ibond.com>, Martin Brandenburg <martin@...ibond.com>, 
	Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.org>, 
	Ronnie Sahlberg <ronniesahlberg@...il.com>, Shyam Prasad N <sprasad@...rosoft.com>, 
	Tom Talpey <tom@...pey.com>, Bharath SM <bharathsm@...rosoft.com>, 
	Zhihao Cheng <chengzhihao1@...wei.com>, Hans de Goede <hdegoede@...hat.com>, 
	Carlos Maiolino <cem@...nel.org>, Damien Le Moal <dlemoal@...nel.org>, 
	Naohiro Aota <naohiro.aota@....com>, Johannes Thumshirn <jth@...nel.org>, 
	Dan Williams <dan.j.williams@...el.com>, Matthew Wilcox <willy@...radead.org>, 
	Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, v9fs@...ts.linux.dev, linux-fsdevel@...r.kernel.org, 
	linux-afs@...ts.infradead.org, linux-aio@...ck.org, linux-unionfs@...r.kernel.org, 
	linux-bcachefs@...r.kernel.org, linux-mm@...ck.org, linux-btrfs@...r.kernel.org, 
	ceph-devel@...r.kernel.org, codalist@...a.cs.cmu.edu, ecryptfs@...r.kernel.org, 
	linux-erofs@...ts.ozlabs.org, linux-ext4@...r.kernel.org, 
	linux-f2fs-devel@...ts.sourceforge.net, linux-um@...ts.infradead.org, linux-mtd@...ts.infradead.org, 
	jfs-discussion@...ts.sourceforge.net, linux-nfs@...r.kernel.org, linux-nilfs@...r.kernel.org, 
	ntfs3@...ts.linux.dev, ocfs2-devel@...ts.linux.dev, 
	linux-karma-devel@...ts.sourceforge.net, devel@...ts.orangefs.org, linux-cifs@...r.kernel.org, 
	samba-technical@...ts.samba.org, linux-xfs@...r.kernel.org, nvdimm@...ts.linux.dev
Subject: Re: [PATCH 05/10] fs/ext4: transition from deprecated .mmap hook to
 .mmap_prepare

On Mon 16-06-25 20:33:24, Lorenzo Stoakes wrote:
> Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
> callback"), the f_op->mmap() hook has been deprecated in favour of
> f_op->mmap_prepare().
> 
> This callback is invoked in the mmap() logic far earlier, so error handling
> can be performed more safely without complicated and bug-prone state
> unwinding required should an error arise.
> 
> This hook also avoids passing a pointer to a not-yet-correctly-established
> VMA avoiding any issues with referencing this data structure.
> 
> It rather provides a pointer to the new struct vm_area_desc descriptor type
> which contains all required state and allows easy setting of required
> parameters without any consideration needing to be paid to locking or
> reference counts.
> 
> Note that nested filesystems like overlayfs are compatible with an
> .mmap_prepare() callback since commit bb666b7c2707 ("mm: add mmap_prepare()
> compatibility layer for nested file systems").
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/file.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 08a814fcd956..38180e527dbe 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -804,9 +804,10 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
>  	.page_mkwrite   = ext4_page_mkwrite,
>  };
>  
> -static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
> +static int ext4_file_mmap_prepare(struct vm_area_desc *desc)
>  {
>  	int ret;
> +	struct file *file = desc->file;
>  	struct inode *inode = file->f_mapping->host;
>  	struct dax_device *dax_dev = EXT4_SB(inode->i_sb)->s_daxdev;
>  
> @@ -821,15 +822,15 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
>  	 * We don't support synchronous mappings for non-DAX files and
>  	 * for DAX files if underneath dax_device is not synchronous.
>  	 */
> -	if (!daxdev_mapping_supported(vma->vm_flags, vma->vm_file, dax_dev))
> +	if (!daxdev_mapping_supported(desc->vm_flags, file, dax_dev))
>  		return -EOPNOTSUPP;
>  
>  	file_accessed(file);
>  	if (IS_DAX(file_inode(file))) {
> -		vma->vm_ops = &ext4_dax_vm_ops;
> -		vm_flags_set(vma, VM_HUGEPAGE);
> +		desc->vm_ops = &ext4_dax_vm_ops;
> +		desc->vm_flags |= VM_HUGEPAGE;
>  	} else {
> -		vma->vm_ops = &ext4_file_vm_ops;
> +		desc->vm_ops = &ext4_file_vm_ops;
>  	}
>  	return 0;
>  }
> @@ -968,7 +969,7 @@ const struct file_operations ext4_file_operations = {
>  #ifdef CONFIG_COMPAT
>  	.compat_ioctl	= ext4_compat_ioctl,
>  #endif
> -	.mmap		= ext4_file_mmap,
> +	.mmap_prepare	= ext4_file_mmap_prepare,
>  	.open		= ext4_file_open,
>  	.release	= ext4_release_file,
>  	.fsync		= ext4_sync_file,
> -- 
> 2.49.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

Powered by blists - more mailing lists