[PATCH v5 2/2] erofs: decompress in endio if possible

[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. Also, it makes no sense to apply synchronous
decompression for such case.

Signed-off-by: Huang Jianan <huangjianan@xxxxxxxx>
Signed-off-by: Guo Weichao <guoweichao@xxxxxxxx>
---
 fs/erofs/internal.h |  2 ++
 fs/erofs/super.c    |  1 +
 fs/erofs/zdata.c    | 16 +++++++++++++---
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 67a7ec945686..e325da7be237 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -53,6 +53,8 @@ struct erofs_fs_context {
 
 	/* threshold for decompression synchronously */
 	unsigned int max_sync_decompress_pages;
+	/* decide whether to decompress synchronously */
+	bool readahead_sync_decompress;
 #endif
 	unsigned int mount_opt;
 };
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 6cb356c4217b..b22cea78a9fd 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -706,9 +706,12 @@ 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)
 {
+	struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
+
 	/* wake up the caller thread for sync decompression */
 	if (sync) {
 		unsigned long flags;
@@ -720,8 +723,14 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 		return;
 	}
 
-	if (!atomic_add_return(bios, &io->pending_bios))
-		queue_work(z_erofs_workqueue, &io->u.work);
+	if (!atomic_add_return(bios, &io->pending_bios)) {
+		if (in_atomic() || irqs_disabled()) {
+			queue_work(z_erofs_workqueue, &io->u.work);
+			sbi->ctx.readahead_sync_decompress = true;
+		} else {
+			z_erofs_decompressqueue_work(&io->u.work);
+		}
+	}
 }
 
 static bool z_erofs_page_is_invalidated(struct page *page)
@@ -1333,7 +1342,8 @@ 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