Message-ID: <47a86f09-3e9b-f841-4191-d750feda6642@kernel.org>
Date:   Tue, 6 Sep 2022 23:43:47 +0800
From:   Chao Yu <chao@...nel.org>
To:     Eric Biggers <ebiggers@...nel.org>, linux-fscrypt@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        Matthew Wilcox <willy@...radead.org>,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v2 2/2] fsverity: stop using PG_error to track
 error status

On 2022/8/16 7:50, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> As a step towards freeing the PG_error flag for other uses, change ext4
> and f2fs to stop using PG_error to track verity errors.  Instead, if a
> verity error occurs, just mark the whole bio as failed.  The coarser
> granularity isn't really a problem since it isn't any worse than what
> the block layer provides, and errors from a multi-page readahead aren't
> reported to applications unless a single-page read fails too.
> 
> f2fs supports compression, which makes the f2fs changes a bit more
> complicated than desired, but the basic premise still works.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
>   fs/ext4/readpage.c |  8 ++----
>   fs/f2fs/compress.c | 64 ++++++++++++++++++++++------------------------
>   fs/f2fs/data.c     | 52 ++++++++++++++++++++-----------------
>   fs/verity/verify.c | 12 ++++-----
>   4 files changed, 68 insertions(+), 68 deletions(-)
> 
> diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
> index 5ce4706f68a7c6..e604ea4e102b71 100644
> --- a/fs/ext4/readpage.c
> +++ b/fs/ext4/readpage.c
> @@ -75,14 +75,10 @@ static void __read_end_io(struct bio *bio)
>   	bio_for_each_segment_all(bv, bio, iter_all) {
>   		page = bv->bv_page;
>   
> -		/* PG_error was set if any post_read step failed */
> -		if (bio->bi_status || PageError(page)) {
> +		if (bio->bi_status)
>   			ClearPageUptodate(page);
> -			/* will re-read again later */
> -			ClearPageError(page);
> -		} else {
> +		else
>   			SetPageUptodate(page);
> -		}
>   		unlock_page(page);
>   	}
>   	if (bio->bi_private)
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index 70e97075e535e5..f54fb3bb74197a 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -1715,50 +1715,27 @@ static void f2fs_put_dic(struct decompress_io_ctx *dic, bool in_task)
>   	}
>   }
>   
> -/*
> - * Update and unlock the cluster's pagecache pages, and release the reference to
> - * the decompress_io_ctx that was being held for I/O completion.
> - */
> -static void __f2fs_decompress_end_io(struct decompress_io_ctx *dic, bool failed,
> -				bool in_task)
> +static void f2fs_verify_cluster(struct work_struct *work)
>   {
> +	struct decompress_io_ctx *dic =
> +		container_of(work, struct decompress_io_ctx, verity_work);
>   	int i;
>   
> +	/* Verify, update, and unlock the decompressed pages. */
>   	for (i = 0; i < dic->cluster_size; i++) {
>   		struct page *rpage = dic->rpages[i];
>   
>   		if (!rpage)
>   			continue;
>   
> -		/* PG_error was set if verity failed. */
> -		if (failed || PageError(rpage)) {
> -			ClearPageUptodate(rpage);
> -			/* will re-read again later */
> -			ClearPageError(rpage);
> -		} else {
> +		if (fsverity_verify_page(rpage))
>   			SetPageUptodate(rpage);
> -		}
> +		else
> +			ClearPageUptodate(rpage);
>   		unlock_page(rpage);
>   	}
>   
> -	f2fs_put_dic(dic, in_task);
> -}
> -
> -static void f2fs_verify_cluster(struct work_struct *work)
> -{
> -	struct decompress_io_ctx *dic =
> -		container_of(work, struct decompress_io_ctx, verity_work);
> -	int i;
> -
> -	/* Verify the cluster's decompressed pages with fs-verity. */
> -	for (i = 0; i < dic->cluster_size; i++) {
> -		struct page *rpage = dic->rpages[i];
> -
> -		if (rpage && !fsverity_verify_page(rpage))
> -			SetPageError(rpage);
> -	}
> -
> -	__f2fs_decompress_end_io(dic, false, true);
> +	f2fs_put_dic(dic, true);
>   }
>   
>   /*
> @@ -1768,6 +1745,8 @@ static void f2fs_verify_cluster(struct work_struct *work)
>   void f2fs_decompress_end_io(struct decompress_io_ctx *dic, bool failed,
>   				bool in_task)
>   {
> +	int i;
> +
>   	if (!failed && dic->need_verity) {
>   		/*
>   		 * Note that to avoid deadlocks, the verity work can't be done
> @@ -1777,9 +1756,28 @@ void f2fs_decompress_end_io(struct decompress_io_ctx *dic, bool failed,
>   		 */
>   		INIT_WORK(&dic->verity_work, f2fs_verify_cluster);
>   		fsverity_enqueue_verify_work(&dic->verity_work);
> -	} else {
> -		__f2fs_decompress_end_io(dic, failed, in_task);

Will it be possible to clean up __f2fs_decompress_end_io() and
f2fs_verify_cluster(), they looks almost similar...

> +		return;
> +	}
> +
> +	/* Update and unlock the cluster's pagecache pages. */
> +	for (i = 0; i < dic->cluster_size; i++) {
> +		struct page *rpage = dic->rpages[i];
> +
> +		if (!rpage)
> +			continue;
> +
> +		if (failed)
> +			ClearPageUptodate(rpage);
> +		else
> +			SetPageUptodate(rpage);
> +		unlock_page(rpage);
>   	}
> +
> +	/*
> +	 * Release the reference to the decompress_io_ctx that was being held
> +	 * for I/O completion.
> +	 */
> +	f2fs_put_dic(dic, in_task);
>   }
>   
>   /*
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 93cc2ec51c2aeb..34af260975a2e6 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -119,34 +119,41 @@ struct bio_post_read_ctx {
>   	block_t fs_blkaddr;
>   };
>   
> -static void f2fs_finish_read_bio(struct bio *bio, bool in_task)
> +/*
> + * Update and unlock a bio's pages, and free the bio.
> + *
> + * This marks pages up-to-date only if there was no error in the bio (I/O error,
> + * decryption error, or verity error), as indicated by bio->bi_status.
> + *
> + * "Compressed pages" (pagecache pages backed by a compressed cluster on-disk)
> + * aren't marked up-to-date here, as decompression is done on a per-compression-
> + * cluster basis rather than a per-bio basis.  Instead, we only must do two
> + * things for each compressed page here: call f2fs_end_read_compressed_page()
> + * with failed=true if an error occurred before it would have normally gotten
> + * called (i.e., I/O error or decryption error, but *not* verity error), and
> + * release the bio's reference to the decompress_io_ctx of the page's cluster.
> + */
> +static void f2fs_finish_read_bio(struct bio *bio, bool in_task,
> +				 bool fail_compressed)

Not sure, fail_decompress or fail_decompression may looks more readable?

Thanks,

>   {
>   	struct bio_vec *bv;
>   	struct bvec_iter_all iter_all;
>   
> -	/*
> -	 * 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 (fail_compressed)
>   				f2fs_end_read_compressed_page(page, true, 0,
>   							in_task);
>   			f2fs_put_page_dic(page, in_task);
>   			continue;
>   		}
>   
> -		/* PG_error was set if verity failed. */
> -		if (bio->bi_status || PageError(page)) {
> +		if (bio->bi_status)
>   			ClearPageUptodate(page);
> -			/* will re-read again later */
> -			ClearPageError(page);
> -		} else {
> +		else
>   			SetPageUptodate(page);
> -		}
>   		dec_page_count(F2FS_P_SB(page), __read_io_type(page));
>   		unlock_page(page);
>   	}
> @@ -185,14 +192,17 @@ static void f2fs_verify_bio(struct work_struct *work)
>   			struct page *page = bv->bv_page;
>   
>   			if (!f2fs_is_compressed_page(page) &&
> -			    !fsverity_verify_page(page))
> -				SetPageError(page);
> +			    !fsverity_verify_page(page)) {
> +				bio->bi_status = BLK_STS_IOERR;
> +				break;
> +			}
>   		}
>   	} else {
>   		fsverity_verify_bio(bio);
>   	}
>   
> -	f2fs_finish_read_bio(bio, true);
> +	f2fs_finish_read_bio(bio, true /* in_task */,
> +			     false /* fail_compressed */);
>   }
>   
>   /*
> @@ -212,7 +222,7 @@ static void f2fs_verify_and_finish_bio(struct bio *bio, bool in_task)
>   		INIT_WORK(&ctx->work, f2fs_verify_bio);
>   		fsverity_enqueue_verify_work(&ctx->work);
>   	} else {
> -		f2fs_finish_read_bio(bio, in_task);
> +		f2fs_finish_read_bio(bio, in_task, false /* fail_compressed */);
>   	}
>   }
>   
> @@ -261,7 +271,8 @@ static void f2fs_post_read_work(struct work_struct *work)
>   	struct bio *bio = ctx->bio;
>   
>   	if ((ctx->enabled_steps & STEP_DECRYPT) && !fscrypt_decrypt_bio(bio)) {
> -		f2fs_finish_read_bio(bio, true);
> +		f2fs_finish_read_bio(bio, true /* in_task */,
> +				     true /* fail_compressed */);
>   		return;
>   	}
>   
> @@ -286,7 +297,7 @@ static void f2fs_read_end_io(struct bio *bio)
>   	}
>   
>   	if (bio->bi_status) {
> -		f2fs_finish_read_bio(bio, intask);
> +		f2fs_finish_read_bio(bio, intask, true /* fail_compressed */);
>   		return;
>   	}
>   
> @@ -1083,7 +1094,6 @@ static int f2fs_submit_page_read(struct inode *inode, struct page *page,
>   		bio_put(bio);
>   		return -EFAULT;
>   	}
> -	ClearPageError(page);
>   	inc_page_count(sbi, F2FS_RD_DATA);
>   	f2fs_update_iostat(sbi, FS_DATA_READ_IO, F2FS_BLKSIZE);
>   	__submit_bio(sbi, bio, DATA);
> @@ -2125,7 +2135,6 @@ static int f2fs_read_single_page(struct inode *inode, struct page *page,
>   
>   	inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
>   	f2fs_update_iostat(F2FS_I_SB(inode), FS_DATA_READ_IO, F2FS_BLKSIZE);
> -	ClearPageError(page);
>   	*last_block_in_bio = block_nr;
>   	goto out;
>   out:
> @@ -2274,7 +2283,6 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
>   		inc_page_count(sbi, F2FS_RD_DATA);
>   		f2fs_update_iostat(sbi, FS_DATA_READ_IO, F2FS_BLKSIZE);
>   		f2fs_update_iostat(sbi, FS_CDATA_READ_IO, F2FS_BLKSIZE);
> -		ClearPageError(page);
>   		*last_block_in_bio = blkaddr;
>   	}
>   
> @@ -2291,7 +2299,6 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
>   	for (i = 0; i < cc->cluster_size; i++) {
>   		if (cc->rpages[i]) {
>   			ClearPageUptodate(cc->rpages[i]);
> -			ClearPageError(cc->rpages[i]);
>   			unlock_page(cc->rpages[i]);
>   		}
>   	}
> @@ -2388,7 +2395,6 @@ static int f2fs_mpage_readpages(struct inode *inode,
>   #ifdef CONFIG_F2FS_FS_COMPRESSION
>   set_error_page:
>   #endif
> -			SetPageError(page);
>   			zero_user_segment(page, 0, PAGE_SIZE);
>   			unlock_page(page);
>   		}
> diff --git a/fs/verity/verify.c b/fs/verity/verify.c
> index 14e2fb49cff561..556dfbd4698dea 100644
> --- a/fs/verity/verify.c
> +++ b/fs/verity/verify.c
> @@ -210,9 +210,8 @@ EXPORT_SYMBOL_GPL(fsverity_verify_page);
>    * @bio: the bio to verify
>    *
>    * Verify a set of pages that have just been read from a verity file.  The pages
> - * must be pagecache pages that are still locked and not yet uptodate.  Pages
> - * that fail verification are set to the Error state.  Verification is skipped
> - * for pages already in the Error state, e.g. due to fscrypt decryption failure.
> + * must be pagecache pages that are still locked and not yet uptodate.  If a
> + * page fails verification, then bio->bi_status is set to an error status.
>    *
>    * This is a helper function for use by the ->readahead() method of filesystems
>    * that issue bios to read data directly into the page cache.  Filesystems that
> @@ -254,9 +253,10 @@ void fsverity_verify_bio(struct bio *bio)
>   		unsigned long level0_ra_pages =
>   			min(max_ra_pages, params->level0_blocks - level0_index);
>   
> -		if (!PageError(page) &&
> -		    !verify_page(inode, vi, req, page, level0_ra_pages))
> -			SetPageError(page);
> +		if (!verify_page(inode, vi, req, page, level0_ra_pages)) {
> +			bio->bi_status = BLK_STS_IOERR;
> +			break;
> +		}
>   	}
>   
>   	fsverity_free_hash_request(params->hash_alg, req);

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