[PATCH 0/2] erofs: decompress in endio if possible

[PATCH 0/2] erofs: decompress in endio if possible

[Huang Jianan]

This patch set was separated form erofs: decompress in endio if possible
since it does these things:
- combine dm-verity and erofs workqueue
- change policy of decompression in context of thread 

Huang Jianan (2):
  erofs: use workqueue decompression for atomic contexts only
  erofs: use sync decompression for atomic contexts only

 fs/erofs/internal.h |  2 ++
 fs/erofs/super.c    |  1 +
 fs/erofs/zdata.c    | 15 +++++++++++++--
 3 files changed, 16 insertions(+), 2 deletions(-)

-- 
2.25.1

[PATCH 0/2] erofs: decompress in endio if possible

[Huang Jianan via Linux-erofs]

This patch set was separated form erofs: decompress in endio if possible
since it does these things:
- combine dm-verity and erofs workqueue
- change policy of decompression in context of thread 

Huang Jianan (2):
  erofs: use workqueue decompression for atomic contexts only
  erofs: use sync decompression for atomic contexts only

 fs/erofs/internal.h |  2 ++
 fs/erofs/super.c    |  1 +
 fs/erofs/zdata.c    | 15 +++++++++++++--
 3 files changed, 16 insertions(+), 2 deletions(-)

-- 
2.25.1

[PATCH 1/2] erofs: use workqueue decompression for atomic contexts only

[Huang Jianan]

z_erofs_decompressqueue_endio may not be executed in the atomic
context, for example, when dm-verity is turned on. In this scenario,
data can be decompressed directly to get rid of additional kworker
scheduling overhead.

Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Guo Weichao <guoweichao@oppo.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
---
 fs/erofs/zdata.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 6cb356c4217b..cf2d28582c14 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -706,6 +706,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 	goto out;
 }
 
+static void z_erofs_decompressqueue_work(struct work_struct *work);
 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 				       bool sync, int bios)
 {
@@ -720,8 +721,14 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 		return;
 	}
 
-	if (!atomic_add_return(bios, &io->pending_bios))
+	if (atomic_add_return(bios, &io->pending_bios))
+		return;
+	/* Use workqueue decompression for atomic contexts only */
+	if (in_atomic() || irqs_disabled()) {
 		queue_work(z_erofs_workqueue, &io->u.work);
+		return;
+	}
+	z_erofs_decompressqueue_work(&io->u.work);
 }
 
 static bool z_erofs_page_is_invalidated(struct page *page)
-- 
2.25.1

[PATCH 1/2] erofs: use workqueue decompression for atomic contexts only

[Huang Jianan via Linux-erofs]

z_erofs_decompressqueue_endio may not be executed in the atomic
context, for example, when dm-verity is turned on. In this scenario,
data can be decompressed directly to get rid of additional kworker
scheduling overhead.

Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Guo Weichao <guoweichao@oppo.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
---
 fs/erofs/zdata.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 6cb356c4217b..cf2d28582c14 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -706,6 +706,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 	goto out;
 }
 
+static void z_erofs_decompressqueue_work(struct work_struct *work);
 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 				       bool sync, int bios)
 {
@@ -720,8 +721,14 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 		return;
 	}
 
-	if (!atomic_add_return(bios, &io->pending_bios))
+	if (atomic_add_return(bios, &io->pending_bios))
+		return;
+	/* Use workqueue decompression for atomic contexts only */
+	if (in_atomic() || irqs_disabled()) {
 		queue_work(z_erofs_workqueue, &io->u.work);
+		return;
+	}
+	z_erofs_decompressqueue_work(&io->u.work);
 }
 
 static bool z_erofs_page_is_invalidated(struct page *page)
-- 
2.25.1

[PATCH 2/2] erofs: use sync decompression for atomic contexts only

[Huang Jianan]

Sync decompression was introduced to get rid of additional kworker
scheduling overhead. But there is no such overhead in non-atomic
contexts. Therefore, it should be better to turn off sync decompression
to avoid the current thread waiting in z_erofs_runqueue.

Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Guo Weichao <guoweichao@oppo.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
---
 fs/erofs/internal.h | 2 ++
 fs/erofs/super.c    | 1 +
 fs/erofs/zdata.c    | 8 ++++++--
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 67a7ec945686..fbc4040715be 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -50,6 +50,8 @@ struct erofs_fs_context {
 #ifdef CONFIG_EROFS_FS_ZIP
 	/* current strategy of how to use managed cache */
 	unsigned char cache_strategy;
+	/* strategy of sync decompression (false - auto, true - force on) */
+	bool readahead_sync_decompress;
 
 	/* threshold for decompression synchronously */
 	unsigned int max_sync_decompress_pages;
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index d5a6b9b888a5..0445d09b6331 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -200,6 +200,7 @@ static void erofs_default_options(struct erofs_fs_context *ctx)
 #ifdef CONFIG_EROFS_FS_ZIP
 	ctx->cache_strategy = EROFS_ZIP_CACHE_READAROUND;
 	ctx->max_sync_decompress_pages = 3;
+	ctx->readahead_sync_decompress = false;
 #endif
 #ifdef CONFIG_EROFS_FS_XATTR
 	set_opt(ctx, XATTR_USER);
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index cf2d28582c14..25a0c4890d0a 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -710,6 +710,8 @@ static void z_erofs_decompressqueue_work(struct work_struct *work);
 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 				       bool sync, int bios)
 {
+	struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
+
 	/* wake up the caller thread for sync decompression */
 	if (sync) {
 		unsigned long flags;
@@ -723,9 +725,10 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 
 	if (atomic_add_return(bios, &io->pending_bios))
 		return;
-	/* Use workqueue decompression for atomic contexts only */
+	/* Use workqueue and sync decompression for atomic contexts only */
 	if (in_atomic() || irqs_disabled()) {
 		queue_work(z_erofs_workqueue, &io->u.work);
+		sbi->ctx.readahead_sync_decompress = true;
 		return;
 	}
 	z_erofs_decompressqueue_work(&io->u.work);
@@ -1340,7 +1343,8 @@ static void z_erofs_readahead(struct readahead_control *rac)
 	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
 
 	unsigned int nr_pages = readahead_count(rac);
-	bool sync = (nr_pages <= sbi->ctx.max_sync_decompress_pages);
+	bool sync = (sbi->ctx.readahead_sync_decompress &&
+			nr_pages <= sbi->ctx.max_sync_decompress_pages);
 	struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
 	struct page *page, *head = NULL;
 	LIST_HEAD(pagepool);
-- 
2.25.1

[PATCH 2/2] erofs: use sync decompression for atomic contexts only

[Huang Jianan via Linux-erofs]

Sync decompression was introduced to get rid of additional kworker
scheduling overhead. But there is no such overhead in non-atomic
contexts. Therefore, it should be better to turn off sync decompression
to avoid the current thread waiting in z_erofs_runqueue.

Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Guo Weichao <guoweichao@oppo.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
---
 fs/erofs/internal.h | 2 ++
 fs/erofs/super.c    | 1 +
 fs/erofs/zdata.c    | 8 ++++++--
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 67a7ec945686..fbc4040715be 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -50,6 +50,8 @@ struct erofs_fs_context {
 #ifdef CONFIG_EROFS_FS_ZIP
 	/* current strategy of how to use managed cache */
 	unsigned char cache_strategy;
+	/* strategy of sync decompression (false - auto, true - force on) */
+	bool readahead_sync_decompress;
 
 	/* threshold for decompression synchronously */
 	unsigned int max_sync_decompress_pages;
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index d5a6b9b888a5..0445d09b6331 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -200,6 +200,7 @@ static void erofs_default_options(struct erofs_fs_context *ctx)
 #ifdef CONFIG_EROFS_FS_ZIP
 	ctx->cache_strategy = EROFS_ZIP_CACHE_READAROUND;
 	ctx->max_sync_decompress_pages = 3;
+	ctx->readahead_sync_decompress = false;
 #endif
 #ifdef CONFIG_EROFS_FS_XATTR
 	set_opt(ctx, XATTR_USER);
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index cf2d28582c14..25a0c4890d0a 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -710,6 +710,8 @@ static void z_erofs_decompressqueue_work(struct work_struct *work);
 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 				       bool sync, int bios)
 {
+	struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
+
 	/* wake up the caller thread for sync decompression */
 	if (sync) {
 		unsigned long flags;
@@ -723,9 +725,10 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 
 	if (atomic_add_return(bios, &io->pending_bios))
 		return;
-	/* Use workqueue decompression for atomic contexts only */
+	/* Use workqueue and sync decompression for atomic contexts only */
 	if (in_atomic() || irqs_disabled()) {
 		queue_work(z_erofs_workqueue, &io->u.work);
+		sbi->ctx.readahead_sync_decompress = true;
 		return;
 	}
 	z_erofs_decompressqueue_work(&io->u.work);
@@ -1340,7 +1343,8 @@ static void z_erofs_readahead(struct readahead_control *rac)
 	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
 
 	unsigned int nr_pages = readahead_count(rac);
-	bool sync = (nr_pages <= sbi->ctx.max_sync_decompress_pages);
+	bool sync = (sbi->ctx.readahead_sync_decompress &&
+			nr_pages <= sbi->ctx.max_sync_decompress_pages);
 	struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
 	struct page *page, *head = NULL;
 	LIST_HEAD(pagepool);
-- 
2.25.1

Re: [PATCH 1/2] erofs: use workqueue decompression for atomic contexts only

[Chao Yu]

On 2021/3/17 11:54, Huang Jianan via Linux-erofs wrote:
> z_erofs_decompressqueue_endio may not be executed in the atomic
> context, for example, when dm-verity is turned on. In this scenario,
> data can be decompressed directly to get rid of additional kworker
> scheduling overhead.
> 
> Signed-off-by: Huang Jianan <huangjianan@oppo.com>
> Signed-off-by: Guo Weichao <guoweichao@oppo.com>
> Reviewed-by: Gao Xiang <hsiangkao@redhat.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

Re: [PATCH 1/2] erofs: use workqueue decompression for atomic contexts only

[Chao Yu]

On 2021/3/17 11:54, Huang Jianan via Linux-erofs wrote:
> z_erofs_decompressqueue_endio may not be executed in the atomic
> context, for example, when dm-verity is turned on. In this scenario,
> data can be decompressed directly to get rid of additional kworker
> scheduling overhead.
> 
> Signed-off-by: Huang Jianan <huangjianan@oppo.com>
> Signed-off-by: Guo Weichao <guoweichao@oppo.com>
> Reviewed-by: Gao Xiang <hsiangkao@redhat.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

Re: [PATCH 2/2] erofs: use sync decompression for atomic contexts only

[Chao Yu]

On 2021/3/17 11:54, Huang Jianan via Linux-erofs wrote:
> Sync decompression was introduced to get rid of additional kworker
> scheduling overhead. But there is no such overhead in non-atomic
> contexts. Therefore, it should be better to turn off sync decompression
> to avoid the current thread waiting in z_erofs_runqueue.
> 
> Signed-off-by: Huang Jianan <huangjianan@oppo.com>
> Signed-off-by: Guo Weichao <guoweichao@oppo.com>
> Reviewed-by: Gao Xiang <hsiangkao@redhat.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

Re: [PATCH 2/2] erofs: use sync decompression for atomic contexts only

[Chao Yu]

On 2021/3/17 11:54, Huang Jianan via Linux-erofs wrote:
> Sync decompression was introduced to get rid of additional kworker
> scheduling overhead. But there is no such overhead in non-atomic
> contexts. Therefore, it should be better to turn off sync decompression
> to avoid the current thread waiting in z_erofs_runqueue.
> 
> Signed-off-by: Huang Jianan <huangjianan@oppo.com>
> Signed-off-by: Guo Weichao <guoweichao@oppo.com>
> Reviewed-by: Gao Xiang <hsiangkao@redhat.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,