Re: [PATCH 1/3] fs/9p: remove unecessary and overrestrictive check

From: Dominique Martinet <asmadeus@codewreck.org>
To: Eric Van Hensbergen <ericvh@kernel.org>
Cc: Latchesar Ionkov <lucho@ionkov.net>,
	Christian Schoenebeck <linux_oss@crudebyte.com>,
	v9fs@lists.linux.dev, linux-kernel@vger.kernel.org,
	kernel@pengutronix.de,
	Robert Schwebel <r.schwebel@pengutronix.de>
Subject: Re: [PATCH 1/3] fs/9p: remove unecessary and overrestrictive check
Date: Tue, 18 Jul 2023 11:45:25 +0900	[thread overview]
Message-ID: <ZLX8xUdCRLYj3cjk@codewreck.org> (raw)
In-Reply-To: <20230716-fixes-overly-restrictive-mmap-v1-1-0683b283b932@kernel.org>

Eric Van Hensbergen wrote on Mon, Jul 17, 2023 at 04:29:00PM +0000:
> This eliminates a check for shared that was overrestrictive and
> duplicated a check in generic_file_readonly_mmap.

generic_file_readonly_mmap checks for VM_SHARED + VM_MAYWRITE,
so it isn't exactly "duplicating" the check.. But I agree we don't need
it; we used to have the mmap op be generic_file_readonly_mmap directly
previously.

I'd argue we don't need to invalidate inode pages either if there is no
writeback cache, there shouldn't be anything in it? but that can be done
separately, and extra invalidation won't bring harm anyway.

Reviewed-by: Dominique Martinet <asmadeus@codewreck.org>

> 
> Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>
> ---
>  fs/9p/vfs_file.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 2996fb00387fa..bda3abd6646b8 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -506,8 +506,6 @@ v9fs_file_mmap(struct file *filp, struct vm_area_struct *vma)
>  
>  	if (!(v9ses->cache & CACHE_WRITEBACK)) {
>  		p9_debug(P9_DEBUG_CACHE, "(no mmap mode)");
> -		if (vma->vm_flags & VM_MAYSHARE)
> -			return -ENODEV;
>  		invalidate_inode_pages2(filp->f_mapping);
>  		return generic_file_readonly_mmap(filp, vma);
>  	}
> 

-- 
Dominique Martinet | Asmadeus