Re: [GIT PULL] orangefs pull request for 5.13

From: Matthew Wilcox <willy@infradead.org>
To: Mike Marshall <hubcap@omnibond.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Mike Marshall <hubcapsc@gmail.com>
Subject: Re: [GIT PULL] orangefs pull request for 5.13
Date: Sun, 2 May 2021 23:58:54 +0100	[thread overview]
Message-ID: <20210502225854.GA1847222@casper.infradead.org> (raw)
In-Reply-To: <CAOg9mSQ-p8vJ6LbSeTeNUCfu-PsT2=iS2+Kab-LYCu9h6MUu2A@mail.gmail.com>

On Sun, May 02, 2021 at 04:45:19PM -0400, Mike Marshall wrote:
> orangefs: implement orangefs_readahead
> 
> mm/readahead.c/read_pages was quite a bit different back
> when I put my open-coded readahead logic into orangefs_readpage.
> It seemed to work as designed then, it is a trainwreck now.

Hey Mike,

I happened to have a chance to look at orangefs_readahead today, and
I'd like to suggest a minor improvement.

It's possible for rac->file to be NULL if the caller doesn't have a
struct file.  I think that only happens when filesystems call their own
readahead routine internally, but in case it might happen from generic
code in the future, I recommend you do something like ...

-       struct file *file = rac->file;
-       struct inode *inode = file->f_mapping->host;
+       struct inode *inode = rac->mapping->host;
...
-       i_pages = &file->f_mapping->i_pages;
+       i_pages = &rac->mapping->i_pages;
...
-                       inode->i_size, NULL, NULL, file)) < 0)
+                       inode->i_size, NULL, NULL, rac->file)) < 0)

(i have this change all tangled up with some other changes in my tree,
so no easy patch to apply, sorry)