Re: [PATCH 1/2] btrfs: enable cross-folio readahead for bs < ps and large folio cases

[David Sterba <dsterba@suse.cz>]

On Tue, Apr 28, 2026 at 07:24:00AM +0930, Qu Wenruo wrote:
> 
> 
> 在 2026/4/27 22:51, David Sterba 写道:
> > On Sun, Apr 26, 2026 at 05:21:03PM +0930, Qu Wenruo wrote:
> >> --- a/fs/btrfs/compression.c
> >> +++ b/fs/btrfs/compression.c
> >> @@ -358,10 +358,7 @@ struct compressed_bio *btrfs_alloc_compressed_write(struct btrfs_inode *inode,
> >>    * Add extra pages in the same compressed file extent so that we don't need to
> >>    * re-read the same extent again and again.
> >>    *
> >> - * NOTE: this won't work well for subpage, as for subpage read, we lock the
> >> - * full page then submit bio for each compressed/regular extents.
> >> - *
> >> - * This means, if we have several sectors in the same page points to the same
> >> + * If we have several sectors in the same page points to the same
> > 
> > The sentence seems to be missing some words, or I don't understand
> > what's the meaning here.
> 
> This means the situation like the following:
> 
>        |      Folio range       |
>        | Ext A|    | Ext B|
> 
> Where Ext A and B are backed by the same compressed extent.
> 
> In that case, if we're reading Ext A, the readahead won't work for Ext B.

Ok, so it should read "If we have several sectors inthe same page
that points to the same ...".