Re: [GIT PULL] orangefs pull request for 5.13

[Matthew Wilcox <willy@infradead.org>]

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)