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Subject: Re: [PATCH 2/2] f2fs: support data compression
To:     Jaegeuk Kim <jaegeuk@kernel.org>
References: <20191022171602.93637-1-jaegeuk@kernel.org>
 <20191022171602.93637-2-jaegeuk@kernel.org>
 <20191027225006.GA321938@sol.localdomain>
 <da214cdc-0074-b7bf-7761-d4c4ad3d4f6a@huawei.com>
 <20191030025512.GA4791@sol.localdomain>
 <97c33fa1-15af-b319-29a1-22f254a26c0a@huawei.com>
 <20191030170246.GB693@sol.localdomain>
From:   Chao Yu <yuchao0@huawei.com>
CC:     <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        Eric Biggers <ebiggers@kernel.org>
Message-ID: <899f99e9-fdc7-a84b-14ec-623fa3a5e164@huawei.com>
Date:   Wed, 13 Nov 2019 21:10:36 +0800
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Hi Jaegeuk,

I've split workqueue for fsverity, please test compression based on last patch.

I shutdown F2FS_FS_COMPRESSION config, it looks all verity testcases can pass, will
do more test for compress/encrypt/fsverity combination later.

The diff is as below, code base is last g-dev-test branch:

From 5b51682bc3013b8de6dee4906865181c3ded435f Mon Sep 17 00:00:00 2001
From: Chao Yu <yuchao0@huawei.com>
Date: Tue, 12 Nov 2019 10:03:21 +0800
Subject: [PATCH INCREMENT] f2fs: compress: split workqueue for fsverity

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
 fs/f2fs/compress.c | 16 +++++---
 fs/f2fs/data.c     | 94 +++++++++++++++++++++++++++++++++++-----------
 fs/f2fs/f2fs.h     |  2 +-
 3 files changed, 84 insertions(+), 28 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index f4ce825f12b4..254275325890 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -377,7 +377,7 @@ void f2fs_decompress_pages(struct bio *bio, struct page *page, bool verity)

 	dec_page_count(sbi, F2FS_RD_DATA);

-	if (bio->bi_status)
+	if (bio->bi_status || PageError(page))
 		dic->failed = true;

 	if (refcount_dec_not_one(&dic->ref))
@@ -419,10 +419,14 @@ void f2fs_decompress_pages(struct bio *bio, struct page *page, bool verity)
 out_vunmap_rbuf:
 	vunmap(dic->rbuf);
 out_free_dic:
-	f2fs_set_cluster_uptodate(dic->rpages, dic->cluster_size, ret, verity);
+	if (!verity)
+		f2fs_decompress_end_io(dic->rpages, dic->cluster_size,
+								ret, false);
+
 	trace_f2fs_decompress_pages_end(dic->inode, dic->cluster_idx,
-								dic->clen, ret);
-	f2fs_free_dic(dic);
+							dic->clen, ret);
+	if (!verity)
+		f2fs_free_dic(dic);
 }

 static bool is_page_in_cluster(struct compress_ctx *cc, pgoff_t index)
@@ -1086,7 +1090,7 @@ void f2fs_free_dic(struct decompress_io_ctx *dic)
 	kfree(dic);
 }

-void f2fs_set_cluster_uptodate(struct page **rpages,
+void f2fs_decompress_end_io(struct page **rpages,
 			unsigned int cluster_size, bool err, bool verity)
 {
 	int i;
@@ -1108,4 +1112,4 @@ void f2fs_set_cluster_uptodate(struct page **rpages,
 		}
 		unlock_page(rpage);
 	}
-}
+}
\ No newline at end of file
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index c9362a53f8a1..2d64c6ffee84 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -98,7 +98,7 @@ static void __read_end_io(struct bio *bio, bool compr, bool verity)
 		page = bv->bv_page;

 #ifdef CONFIG_F2FS_FS_COMPRESSION
-		if (compr && PagePrivate(page)) {
+		if (compr && f2fs_is_compressed_page(page)) {
 			f2fs_decompress_pages(bio, page, verity);
 			continue;
 		}
@@ -115,9 +115,14 @@ static void __read_end_io(struct bio *bio, bool compr, bool verity)
 		dec_page_count(F2FS_P_SB(page), __read_io_type(page));
 		unlock_page(page);
 	}
-	if (bio->bi_private)
-		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
-	bio_put(bio);
+}
+
+static void f2fs_release_read_bio(struct bio *bio);
+static void __f2fs_read_end_io(struct bio *bio, bool compr, bool verity)
+{
+	if (!compr)
+		__read_end_io(bio, false, verity);
+	f2fs_release_read_bio(bio);
 }

 static void f2fs_decompress_bio(struct bio *bio, bool verity)
@@ -127,19 +132,50 @@ static void f2fs_decompress_bio(struct bio *bio, bool verity)

 static void bio_post_read_processing(struct bio_post_read_ctx *ctx);

-static void decrypt_work(struct bio_post_read_ctx *ctx)
+static void f2fs_decrypt_work(struct bio_post_read_ctx *ctx)
 {
 	fscrypt_decrypt_bio(ctx->bio);
 }

-static void decompress_work(struct bio_post_read_ctx *ctx, bool verity)
+static void f2fs_decompress_work(struct bio_post_read_ctx *ctx)
+{
+	f2fs_decompress_bio(ctx->bio, ctx->enabled_steps & (1 << STEP_VERITY));
+}
+
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+void f2fs_verify_pages(struct page **rpages, unsigned int cluster_size)
 {
-	f2fs_decompress_bio(ctx->bio, verity);
+	f2fs_decompress_end_io(rpages, cluster_size, false, true);
 }

-static void verity_work(struct bio_post_read_ctx *ctx)
+static void f2fs_verify_bio(struct bio *bio)
 {
+	struct page *page = bio_first_page_all(bio);
+	struct decompress_io_ctx *dic =
+			(struct decompress_io_ctx *)page_private(page);
+
+	f2fs_verify_pages(dic->rpages, dic->cluster_size);
+	f2fs_free_dic(dic);
+}
+#endif
+
+static void f2fs_verity_work(struct work_struct *work)
+{
+	struct bio_post_read_ctx *ctx =
+		container_of(work, struct bio_post_read_ctx, work);
+
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+	/* previous step is decompression */
+	if (ctx->enabled_steps & (1 << STEP_DECOMPRESS)) {
+
+		f2fs_verify_bio(ctx->bio);
+		f2fs_release_read_bio(ctx->bio);
+		return;
+	}
+#endif
+
 	fsverity_verify_bio(ctx->bio);
+	__f2fs_read_end_io(ctx->bio, false, false);
 }

 static void f2fs_post_read_work(struct work_struct *work)
@@ -148,18 +184,19 @@ static void f2fs_post_read_work(struct work_struct *work)
 		container_of(work, struct bio_post_read_ctx, work);

 	if (ctx->enabled_steps & (1 << STEP_DECRYPT))
-		decrypt_work(ctx);
+		f2fs_decrypt_work(ctx);

-	if (ctx->enabled_steps & (1 << STEP_DECOMPRESS)) {
-		decompress_work(ctx,
-			ctx->enabled_steps & (1 << STEP_VERITY));
+	if (ctx->enabled_steps & (1 << STEP_DECOMPRESS))
+		f2fs_decompress_work(ctx);
+
+	if (ctx->enabled_steps & (1 << STEP_VERITY)) {
+		INIT_WORK(&ctx->work, f2fs_verity_work);
+		fsverity_enqueue_verify_work(&ctx->work);
 		return;
 	}

-	if (ctx->enabled_steps & (1 << STEP_VERITY))
-		verity_work(ctx);
-
-	__read_end_io(ctx->bio, false, false);
+	__f2fs_read_end_io(ctx->bio,
+		ctx->enabled_steps & (1 << STEP_DECOMPRESS), false);
 }

 static void f2fs_enqueue_post_read_work(struct f2fs_sb_info *sbi,
@@ -176,12 +213,20 @@ static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
 	 * we shouldn't recurse to the same workqueue.
 	 */

-	if (ctx->enabled_steps) {
+	if (ctx->enabled_steps & (1 << STEP_DECRYPT) ||
+		ctx->enabled_steps & (1 << STEP_DECOMPRESS)) {
 		INIT_WORK(&ctx->work, f2fs_post_read_work);
 		f2fs_enqueue_post_read_work(ctx->sbi, &ctx->work);
 		return;
 	}
-	__read_end_io(ctx->bio, false, false);
+
+	if (ctx->enabled_steps & (1 << STEP_VERITY)) {
+		INIT_WORK(&ctx->work, f2fs_verity_work);
+		fsverity_enqueue_verify_work(&ctx->work);
+		return;
+	}
+
+	__f2fs_read_end_io(ctx->bio, false, false);
 }

 static bool f2fs_bio_post_read_required(struct bio *bio)
@@ -205,7 +250,7 @@ static void f2fs_read_end_io(struct bio *bio)
 		return;
 	}

-	__read_end_io(bio, false, false);
+	__f2fs_read_end_io(bio, false, false);
 }

 static void f2fs_write_end_io(struct bio *bio)
@@ -864,6 +909,13 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
 	return bio;
 }

+static void f2fs_release_read_bio(struct bio *bio)
+{
+	if (bio->bi_private)
+		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
+	bio_put(bio);
+}
+
 /* This can handle encryption stuffs */
 static int f2fs_submit_page_read(struct inode *inode, struct page *page,
 							block_t blkaddr)
@@ -2023,7 +2075,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 				dic->failed = true;
 				if (refcount_sub_and_test(dic->nr_cpages - i,
 							&dic->ref))
-					f2fs_set_cluster_uptodate(dic->rpages,
+					f2fs_decompress_end_io(dic->rpages,
 							cc->cluster_size, true,
 							false);
 				f2fs_free_dic(dic);
@@ -2053,7 +2105,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 out_put_dnode:
 	f2fs_put_dnode(&dn);
 out:
-	f2fs_set_cluster_uptodate(cc->rpages, cc->cluster_size, true, false);
+	f2fs_decompress_end_io(cc->rpages, cc->cluster_size, true, false);
 	f2fs_destroy_compress_ctx(cc);
 	*bio_ret = bio;
 	return ret;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 8a3a35b42a37..20067fa3b035 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3795,7 +3795,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 				bool is_readahead);
 struct decompress_io_ctx *f2fs_alloc_dic(struct compress_ctx *cc);
 void f2fs_free_dic(struct decompress_io_ctx *dic);
-void f2fs_set_cluster_uptodate(struct page **rpages,
+void f2fs_decompress_end_io(struct page **rpages,
 			unsigned int cluster_size, bool err, bool verity);
 int f2fs_init_compress_ctx(struct compress_ctx *cc);
 void f2fs_destroy_compress_ctx(struct compress_ctx *cc);
-- 
2.18.0.rc1


On 2019/10/31 1:02, Eric Biggers wrote:
> On Wed, Oct 30, 2019 at 04:43:52PM +0800, Chao Yu wrote:
>>>>>>  static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
>>>>>>  {
>>>>>> -	/*
>>>>>> -	 * We use different work queues for decryption and for verity because
>>>>>> -	 * verity may require reading metadata pages that need decryption, and
>>>>>> -	 * we shouldn't recurse to the same workqueue.
>>>>>> -	 */
>>>>>
>>>>> Why is it okay (i.e., no deadlocks) to no longer use different work queues for
>>>>> decryption and for verity?  See the comment above which is being deleted.
>>>>
>>>> Could you explain more about how deadlock happen? or share me a link address if
>>>> you have described that case somewhere?
>>>>
>>>
>>> The verity work can read pages from the file which require decryption.  I'm
>>> concerned that it could deadlock if the work is scheduled on the same workqueue.
>>
>> I assume you've tried one workqueue, and suffered deadlock..
>>
>>> Granted, I'm not an expert in Linux workqueues, so if you've investigated this
>>> and determined that it's safe, can you explain why?
>>
>> I'm not familiar with workqueue...  I guess it may not safe that if the work is
>> scheduled to the same cpu in where verity was waiting for data? if the work is
>> scheduled to other cpu, it may be safe.
>>
>> I can check that before splitting the workqueue for verity and decrypt/decompress.
>>
> 
> Yes this is a real problem, try 'kvm-xfstests -c f2fs/encrypt generic/579'.
> The worker thread gets deadlocked in f2fs_read_merkle_tree_page() waiting for
> the Merkle tree page to be decrypted.  This is with the v2 compression patch;
> it works fine on current mainline.
> 
> INFO: task kworker/u5:0:61 blocked for more than 30 seconds.
>       Not tainted 5.4.0-rc1-00119-g464e31ba60d0 #13
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> kworker/u5:0    D    0    61      2 0x80004000
> Workqueue: f2fs_post_read_wq f2fs_post_read_work
> Call Trace:
>  context_switch kernel/sched/core.c:3384 [inline]
>  __schedule+0x299/0x6c0 kernel/sched/core.c:4069
>  schedule+0x44/0xd0 kernel/sched/core.c:4136
>  io_schedule+0x11/0x40 kernel/sched/core.c:5780
>  wait_on_page_bit_common mm/filemap.c:1174 [inline]
>  wait_on_page_bit mm/filemap.c:1223 [inline]
>  wait_on_page_locked include/linux/pagemap.h:527 [inline]
>  wait_on_page_locked include/linux/pagemap.h:524 [inline]
>  wait_on_page_read mm/filemap.c:2767 [inline]
>  do_read_cache_page+0x407/0x660 mm/filemap.c:2810
>  read_cache_page+0xd/0x10 mm/filemap.c:2894
>  f2fs_read_merkle_tree_page+0x2e/0x30 include/linux/pagemap.h:396
>  verify_page+0x110/0x560 fs/verity/verify.c:120
>  fsverity_verify_bio+0xe6/0x1a0 fs/verity/verify.c:239
>  verity_work fs/f2fs/data.c:142 [inline]
>  f2fs_post_read_work+0x36/0x50 fs/f2fs/data.c:160
>  process_one_work+0x225/0x550 kernel/workqueue.c:2269
>  worker_thread+0x4b/0x3c0 kernel/workqueue.c:2415
>  kthread+0x125/0x140 kernel/kthread.c:255
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> INFO: task kworker/u5:1:1140 blocked for more than 30 seconds.
>       Not tainted 5.4.0-rc1-00119-g464e31ba60d0 #13
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> kworker/u5:1    D    0  1140      2 0x80004000
> Workqueue: f2fs_post_read_wq f2fs_post_read_work
> Call Trace:
>  context_switch kernel/sched/core.c:3384 [inline]
>  __schedule+0x299/0x6c0 kernel/sched/core.c:4069
>  schedule+0x44/0xd0 kernel/sched/core.c:4136
>  io_schedule+0x11/0x40 kernel/sched/core.c:5780
>  wait_on_page_bit_common mm/filemap.c:1174 [inline]
>  wait_on_page_bit mm/filemap.c:1223 [inline]
>  wait_on_page_locked include/linux/pagemap.h:527 [inline]
>  wait_on_page_locked include/linux/pagemap.h:524 [inline]
>  wait_on_page_read mm/filemap.c:2767 [inline]
>  do_read_cache_page+0x407/0x660 mm/filemap.c:2810
>  read_cache_page+0xd/0x10 mm/filemap.c:2894
>  f2fs_read_merkle_tree_page+0x2e/0x30 include/linux/pagemap.h:396
>  verify_page+0x110/0x560 fs/verity/verify.c:120
>  fsverity_verify_bio+0xe6/0x1a0 fs/verity/verify.c:239
>  verity_work fs/f2fs/data.c:142 [inline]
>  f2fs_post_read_work+0x36/0x50 fs/f2fs/data.c:160
>  process_one_work+0x225/0x550 kernel/workqueue.c:2269
>  worker_thread+0x4b/0x3c0 kernel/workqueue.c:2415
>  kthread+0x125/0x140 kernel/kthread.c:255
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> Showing all locks held in the system:
> 1 lock held by khungtaskd/21:
>  #0: ffffffff82250520 (rcu_read_lock){....}, at: rcu_lock_acquire.constprop.0+0x0/0x30 include/trace/events/lock.h:13
> 2 locks held by kworker/u5:0/61:
>  #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline]
>  #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
>  #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240
>  #1: ffffc90000253e50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline]
>  #1: ffffc90000253e50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
>  #1: ffffc90000253e50 ((work_completion)(&ctx->work)){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240
> 2 locks held by kworker/u5:1/1140:
>  #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline]
>  #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
>  #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240
>  #1: ffffc9000174be50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline]
>  #1: ffffc9000174be50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
>  #1: ffffc9000174be50 ((work_completion)(&ctx->work)){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240
> .
>