Re: [RFC PATCH 09/11] iomap: fs-verity verification on page read

[Andrey Albershteyn <aalbersh@redhat.com>]

On Tue, Dec 13, 2022 at 11:02:59AM -0800, Eric Biggers wrote:
> On Tue, Dec 13, 2022 at 06:29:33PM +0100, Andrey Albershteyn wrote:
> > Add fs-verity page verification in read IO path. The verification
> > itself is offloaded into workqueue (provided by fs-verity).
> > 
> > The work_struct items are allocated from bioset side by side with
> > bio being processed.
> > 
> > As inodes with fs-verity doesn't use large folios we check only
> > first page of the folio for errors (set by fs-verity if verification
> > failed).
> > 
> > Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
> > ---
> >  fs/iomap/buffered-io.c | 80 +++++++++++++++++++++++++++++++++++++++---
> >  include/linux/iomap.h  |  5 +++
> >  2 files changed, 81 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > index 91ee0b308e13d..b7abc2f806cfc 100644
> > --- a/fs/iomap/buffered-io.c
> > +++ b/fs/iomap/buffered-io.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/bio.h>
> >  #include <linux/sched/signal.h>
> >  #include <linux/migrate.h>
> > +#include <linux/fsverity.h>
> >  #include "trace.h"
> >  
> >  #include "../internal.h"
> > @@ -42,6 +43,7 @@ static inline struct iomap_page *to_iomap_page(struct folio *folio)
> >  }
> >  
> >  static struct bio_set iomap_ioend_bioset;
> > +static struct bio_set iomap_readend_bioset;
> >  
> >  static struct iomap_page *
> >  iomap_page_create(struct inode *inode, struct folio *folio, unsigned int flags)
> > @@ -189,9 +191,39 @@ static void iomap_read_end_io(struct bio *bio)
> >  	int error = blk_status_to_errno(bio->bi_status);
> >  	struct folio_iter fi;
> >  
> > -	bio_for_each_folio_all(fi, bio)
> > +	bio_for_each_folio_all(fi, bio) {
> > +		/*
> > +		 * As fs-verity doesn't work with multi-page folios, verity
> > +		 * inodes have large folios disabled (only single page folios
> > +		 * are used)
> > +		 */
> > +		if (!error)
> > +			error = PageError(folio_page(fi.folio, 0));
> > +
> >  		iomap_finish_folio_read(fi.folio, fi.offset, fi.length, error);
> > +	}
> 
> fs/verity/ no longer uses PG_error to report errors.  See upstream commit
> 98dc08bae678 ("fsverity: stop using PG_error to track error status").

Thanks! Missed that.

> 
> - Eric
> 

-- 
- Andrey