linux-ext4 - Re: [PATCH v4] fsverity: stop using PG

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Date:   Mon, 28 Nov 2022 23:14:25 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        Matthew Wilcox <willy@...radead.org>, Chao Yu <chao@...nel.org>
Subject: Re: [PATCH v4] fsverity: stop using PG_error to track error status

On Mon, Nov 28, 2022 at 10:48:41PM -0800, Jaegeuk Kim wrote:
> >  static void f2fs_finish_read_bio(struct bio *bio, bool in_task)
> >  {
> >  	struct bio_vec *bv;
> >  	struct bvec_iter_all iter_all;
> > +	struct bio_post_read_ctx *ctx = bio->bi_private;
> >  
> > -	/*
> > -	 * Update and unlock the bio's pagecache pages, and put the
> > -	 * decompression context for any compressed pages.
> > -	 */
> >  	bio_for_each_segment_all(bv, bio, iter_all) {
> >  		struct page *page = bv->bv_page;
> >  
> >  		if (f2fs_is_compressed_page(page)) {
> > -			if (bio->bi_status)
> > +			if (!ctx->decompression_attempted)
> 
> If seems this causes a panic due to the ctx nullified by f2fs_verify_bio.
> 

Thanks for catching that!  I've sent out v5 that checks for 'ctx &&
!ctx->decompression_attempted' here.  That's the right thing to do, since if ctx
is NULL then decompression must have been attempted.

I'd like to get rid of freeing the bio_post_read_ctx in f2fs_verify_bio().
But I believe it's still needed, at least in theory.

Do you have a suggestion for testing f2fs compression + verity with xfstests?
I missed this because compression isn't covered by the "verity" group tests.
Maybe there should be an "f2fs/compress" config in xfstests-bld that uses mkfs
and mount options that cause all files to be automatically compressed, similar
to how f2fs/encrypt automatically encrypts all files with test_dummy_encryption.

- Eric