linux-kernel - Re: [RFC PATCH 01/12] afs: Sort out symlink reading

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Message-ID: <35ecb577315f486f1636b2316c2051ad004f6f7b.camel@redhat.com>
Date:   Wed, 21 Jul 2021 12:20:42 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     David Howells <dhowells@...hat.com>, linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <sfrench@...ba.org>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Mike Marshall <hubcap@...ibond.com>,
        David Wysochanski <dwysocha@...hat.com>,
        Shyam Prasad N <nspmangalore@...il.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-cachefs@...hat.com, linux-afs@...ts.infradead.org,
        linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org,
        ceph-devel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
        devel@...ts.orangefs.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 01/12] afs: Sort out symlink reading

On Wed, 2021-07-21 at 14:44 +0100, David Howells wrote:
> afs_readpage() doesn't get a file pointer when called for a symlink, so
> separate it from regular file pointer handling.
> 
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
> 
>  fs/afs/file.c     |   14 +++++++++-----
>  fs/afs/inode.c    |    6 +++---
>  fs/afs/internal.h |    3 ++-
>  3 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/afs/file.c b/fs/afs/file.c
> index ca0d993add65..c9c21ad0e7c9 100644
> --- a/fs/afs/file.c
> +++ b/fs/afs/file.c
> @@ -19,6 +19,7 @@
>  
>  static int afs_file_mmap(struct file *file, struct vm_area_struct *vma);
>  static int afs_readpage(struct file *file, struct page *page);
> +static int afs_symlink_readpage(struct file *file, struct page *page);
>  static void afs_invalidatepage(struct page *page, unsigned int offset,
>  			       unsigned int length);
>  static int afs_releasepage(struct page *page, gfp_t gfp_flags);
> @@ -46,7 +47,7 @@ const struct inode_operations afs_file_inode_operations = {
>  	.permission	= afs_permission,
>  };
>  
> -const struct address_space_operations afs_fs_aops = {
> +const struct address_space_operations afs_file_aops = {
>  	.readpage	= afs_readpage,
>  	.readahead	= afs_readahead,
>  	.set_page_dirty	= afs_set_page_dirty,
> @@ -60,6 +61,12 @@ const struct address_space_operations afs_fs_aops = {
>  	.writepages	= afs_writepages,
>  };
>  
> +const struct address_space_operations afs_symlink_aops = {
> +	.readpage	= afs_symlink_readpage,
> +	.releasepage	= afs_releasepage,
> +	.invalidatepage	= afs_invalidatepage,
> +};
> +
>  static const struct vm_operations_struct afs_vm_ops = {
>  	.fault		= filemap_fault,
>  	.map_pages	= filemap_map_pages,
> @@ -321,7 +328,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>  	afs_fetch_data(fsreq->vnode, fsreq);
>  }
>  
> -static int afs_symlink_readpage(struct page *page)
> +static int afs_symlink_readpage(struct file *file, struct page *page)
>  {
>  	struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
>  	struct afs_read *fsreq;


I wonder...would you be better served here by not using page_readlink
for symlinks and instead use simple_get_link and roll your own readlink
operation. It seems a bit more direct, and AFS seems to be the only
caller of page_readlink.

> @@ -386,9 +393,6 @@ const struct netfs_read_request_ops afs_req_ops = {
>  
>  static int afs_readpage(struct file *file, struct page *page)
>  {
> -	if (!file)
> -		return afs_symlink_readpage(page);
> -
>  	return netfs_readpage(file, page, &afs_req_ops, NULL);
>  }
>  
> diff --git a/fs/afs/inode.c b/fs/afs/inode.c
> index bef6f5ccfb09..cf7b66957c6f 100644
> --- a/fs/afs/inode.c
> +++ b/fs/afs/inode.c
> @@ -105,7 +105,7 @@ static int afs_inode_init_from_status(struct afs_operation *op,
>  		inode->i_mode	= S_IFREG | (status->mode & S_IALLUGO);
>  		inode->i_op	= &afs_file_inode_operations;
>  		inode->i_fop	= &afs_file_operations;
> -		inode->i_mapping->a_ops	= &afs_fs_aops;
> +		inode->i_mapping->a_ops	= &afs_file_aops;
>  		break;
>  	case AFS_FTYPE_DIR:
>  		inode->i_mode	= S_IFDIR |  (status->mode & S_IALLUGO);
> @@ -123,11 +123,11 @@ static int afs_inode_init_from_status(struct afs_operation *op,
>  			inode->i_mode	= S_IFDIR | 0555;
>  			inode->i_op	= &afs_mntpt_inode_operations;
>  			inode->i_fop	= &afs_mntpt_file_operations;
> -			inode->i_mapping->a_ops	= &afs_fs_aops;
> +			inode->i_mapping->a_ops	= &afs_symlink_aops;
>  		} else {
>  			inode->i_mode	= S_IFLNK | status->mode;
>  			inode->i_op	= &afs_symlink_inode_operations;
> -			inode->i_mapping->a_ops	= &afs_fs_aops;
> +			inode->i_mapping->a_ops	= &afs_symlink_aops;
>  		}
>  		inode_nohighmem(inode);
>  		break;
> diff --git a/fs/afs/internal.h b/fs/afs/internal.h
> index 791cf02e5696..ccdde00ada8a 100644
> --- a/fs/afs/internal.h
> +++ b/fs/afs/internal.h
> @@ -1050,7 +1050,8 @@ extern void afs_dynroot_depopulate(struct super_block *);
>  /*
>   * file.c
>   */
> -extern const struct address_space_operations afs_fs_aops;
> +extern const struct address_space_operations afs_file_aops;
> +extern const struct address_space_operations afs_symlink_aops;
>  extern const struct inode_operations afs_file_inode_operations;
>  extern const struct file_operations afs_file_operations;
>  extern const struct netfs_read_request_ops afs_req_ops;
> 
> 

Regardless, this is more reasonable than what's there now.

Reviewed-by: Jeff Layton <jlayton@...hat.com>