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From:   Christian Schoenebeck <linux_oss@crudebyte.com>
To:     Eric Van Hensbergen <ericvh@kernel.org>,
        Dominique Martinet <asmadeus@codewreck.org>
Cc:     Latchesar Ionkov <lucho@ionkov.net>, 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 11:17:16 +0200
Message-ID: <9085752.7RgNvelpzP@silver>
In-Reply-To: <ZLX8xUdCRLYj3cjk@codewreck.org>
References: <20230716-fixes-overly-restrictive-mmap-v1-0-0683b283b932@kernel.org>
 <20230716-fixes-overly-restrictive-mmap-v1-1-0683b283b932@kernel.org>
 <ZLX8xUdCRLYj3cjk@codewreck.org>
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On Tuesday, July 18, 2023 4:45:25 AM CEST Dominique Martinet wrote:
> 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.

It should be removed from the commit log then though.

> 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.

Unnecessary performance penalty? So I would drop that in a separate patch.

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

Feel free to add my RB as well:

Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>

> > 
> > 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);
> >  	}
> > 
> 
>