Re: [PATCH] erofs: use the shared page cache for splice in inode_share mode

[Gao Xiang <xiang@kernel.org>]

On Thu, Aug 20, 2026 at 09:34:49PM +0800, Jingbo Xu wrote:
> 
> 
> On 8/20/26 8:37 PM, Zhan Xusheng wrote:
> > On Thu, 20 Aug 2026 17:53:20 +0800, Jingbo Xu wrote:
> >> Please refer to backing_file_splice_read() called from
> >> ovl_splice_read(), file_accessed() needs to be called on the original
> >> file (just as what .read_iter() i.e. filemap_read() does), and the input
> >> @ppos needs to be updated accordingly.
> > 
> > Taking the file_accessed() one, thanks.  filemap_splice_read() calls it at
> > mm/filemap.c:3155 on whatever file it was handed, so on the backing file,
> > whereas backing_file_splice_read() ends in ctx->accessed(iocb->ki_filp),
> > which for ovl_splice_read() is the original.  v2 adds file_accessed(in).
> > 
> > @ppos looks already handled to me.  filemap_splice_read() takes a loff_t *
> > and advances it itself, at mm/filemap.c:3144; its internal kiocb is seeded
> > from *ppos at 3083 and 3098, not the other way round.  ovl_splice_read()
> > has to copy iocb.ki_pos back because backing_file_splice_read() takes a
> > struct kiocb and hands &iocb->ki_pos to vfs_splice_read().  Say if I have
> > that wrong.
> 
> Make sense.
> 
> 
> > 
> > One you may want for read_iter too: it clones the kiocb onto the backing
> > file, so filemap_read() marks that one accessed rather than the user's
> > file, which is the shape splice_read had.  Neither is observable today,
> > since erofs_fc_fill_super() sets SB_RDONLY | SB_NOATIME and the backing
> > file is opened O_NOATIME, so both reach a no-op.  That is why I left
> > read_iter alone here.
> 
> Okay, it seems that file_accessed() shall also be added to
> erofs_ishare_file_read_iter()?

I think file_accessed() is a no-op for erofs?

Thanks,
Gao Xiang

> 
> 
> -- 
> Thanks,
> Jingbo
> 
>