[PREVIEW] [PATCH 1/3] staging: erofs: cleanup z_erofs_vle_normalaccess_readpages

[PREVIEW] [PATCH 1/3] staging: erofs: cleanup z_erofs_vle_normalaccess_readpages

[Gao Xiang]

This patch introduces __should_decompress_synchronously to
cleanup z_erofs_vle_normalaccess_readpages.

Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
---

Hi,

These patches are based on commit
staging: erofs: add trace points for reading zipped data

several cleanups for the upcoming bugfixes.

Thanks,
Gao Xiang

 drivers/staging/erofs/internal.h  | 11 +++++++++++
 drivers/staging/erofs/super.c     |  5 +++++
 drivers/staging/erofs/unzip_vle.c | 20 ++++++--------------
 3 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
index 8951e01..bd2987a 100644
--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -95,6 +95,9 @@ struct erofs_sb_info {
 	/* the dedicated workstation for compression */
 	struct radix_tree_root workstn_tree;
 
+	/* threshold for decompression synchronously */
+	unsigned int min_async_decompress_pages;
+
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
 	struct inode *managed_cache;
 #endif
@@ -266,6 +269,14 @@ extern int erofs_try_to_free_cached_page(struct address_space *mapping,
 	struct page *page);
 #endif
 
+#define DEFAULT_MIN_ASYNC_DECOMPRESS_PAGES	5
+
+static inline bool __should_decompress_synchronously(struct erofs_sb_info *sbi,
+						     unsigned int nr)
+{
+	return nr < sbi->min_async_decompress_pages;
+}
+
 #endif
 
 /* we strictly follow PAGE_SIZE and no buffer head yet */
diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
index 93548b9..708211d 100644
--- a/drivers/staging/erofs/super.c
+++ b/drivers/staging/erofs/super.c
@@ -162,6 +162,11 @@ static void erofs_build_fault_attr(struct erofs_sb_info *sbi,
 
 static void default_options(struct erofs_sb_info *sbi)
 {
+	/* set up some FS parameters */
+#ifdef CONFIG_EROFS_FS_ZIP
+	sbi->min_async_decompress_pages = DEFAULT_MIN_ASYNC_DECOMPRESS_PAGES;
+#endif
+
 #ifdef CONFIG_EROFS_FS_XATTR
 	set_opt(sbi, XATTR_USER);
 #endif
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 3cd0c10..391277f 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -1340,12 +1340,14 @@ static int z_erofs_vle_normalaccess_readpage(struct file *file,
 	return 0;
 }
 
-static inline int __z_erofs_vle_normalaccess_readpages(
-	struct file *filp,
-	struct address_space *mapping,
-	struct list_head *pages, unsigned nr_pages, bool sync)
+static int z_erofs_vle_normalaccess_readpages(struct file *filp,
+					      struct address_space *mapping,
+					      struct list_head *pages,
+					      unsigned int nr_pages)
 {
 	struct inode *const inode = mapping->host;
+	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
+	const bool sync = __should_decompress_synchronously(sbi, nr_pages);
 
 	struct z_erofs_vle_frontend f = VLE_FRONTEND_INIT(inode);
 	gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
@@ -1403,16 +1405,6 @@ static inline int __z_erofs_vle_normalaccess_readpages(
 	return 0;
 }
 
-static int z_erofs_vle_normalaccess_readpages(
-	struct file *filp,
-	struct address_space *mapping,
-	struct list_head *pages, unsigned nr_pages)
-{
-	return __z_erofs_vle_normalaccess_readpages(filp,
-		mapping, pages, nr_pages,
-		nr_pages < 4 /* sync */);
-}
-
 const struct address_space_operations z_erofs_vle_normalaccess_aops = {
 	.readpage = z_erofs_vle_normalaccess_readpage,
 	.readpages = z_erofs_vle_normalaccess_readpages,
-- 
1.9.1

[PREVIEW] [PATCH 2/3] staging: erofs: fold in __update_workgrp_llen

[Gao Xiang]

There is only one user to use __update_workgrp_llen, so
fold it in z_erofs_vle_work_iter_begin and cleanup related code.

Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
---
 drivers/staging/erofs/unzip_vle.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 391277f..016c82d 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -422,18 +422,6 @@ struct z_erofs_vle_work_finder {
 	return work;
 }
 
-static inline void __update_workgrp_llen(struct z_erofs_vle_workgroup *grp,
-					 unsigned int llen)
-{
-	while (1) {
-		unsigned int orig_llen = grp->llen;
-
-		if (orig_llen >= llen || orig_llen ==
-			cmpxchg(&grp->llen, orig_llen, llen))
-			break;
-	}
-}
-
 #define builder_is_followed(builder) \
 	((builder)->role >= Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED)
 
@@ -466,7 +454,13 @@ static int z_erofs_vle_work_iter_begin(struct z_erofs_vle_work_builder *builder,
 repeat:
 	work = z_erofs_vle_work_lookup(&finder);
 	if (work != NULL) {
-		__update_workgrp_llen(grp, map->m_llen);
+		unsigned int orig_llen;
+
+		/* increase workgroup `llen' if needed */
+		while ((orig_llen = READ_ONCE(grp->llen)) < map->m_llen &&
+		       orig_llen != cmpxchg_relaxed(&grp->llen,
+						    orig_llen, map->m_llen))
+			cpu_relax();
 		goto got_it;
 	}
 
-- 
1.9.1

[PREVIEW] [PATCH 3/3] staging: erofs: drop multiref support temporarily

[Gao Xiang]

Multiref support means that a compressed page could have
more than one reference, which is designed for on-disk data
deduplication. However, mkfs doesn't support this mode
at this moment, and the kernel implementation is also broken.

Let's drop multiref support. If it is fully implemented
in the future, it can be reverted later.

Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
---
 drivers/staging/erofs/unzip_vle.c | 36 +++++-------------------------------
 drivers/staging/erofs/unzip_vle.h | 12 +-----------
 2 files changed, 6 insertions(+), 42 deletions(-)

diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 016c82d..6c5739a 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -301,12 +301,9 @@ struct z_erofs_vle_work_finder {
 	grp = container_of(egrp, struct z_erofs_vle_workgroup, obj);
 	*f->grp_ret = grp;
 
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
 	work = z_erofs_vle_grab_work(grp, f->pageofs);
+	/* if multiref is disabled, `primary' is always true */
 	primary = true;
-#else
-	BUG();
-#endif
 
 	DBG_BUGON(work->pageofs != f->pageofs);
 
@@ -368,12 +365,9 @@ struct z_erofs_vle_work_finder {
 	struct z_erofs_vle_workgroup *grp = *f->grp_ret;
 	struct z_erofs_vle_work *work;
 
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
+	/* if multiref is disabled, grp should never be nullptr */
 	BUG_ON(grp != NULL);
-#else
-	if (grp != NULL)
-		goto skip;
-#endif
+
 	/* no available workgroup, let's allocate one */
 	grp = kmem_cache_zalloc(z_erofs_workgroup_cachep, GFP_NOFS);
 	if (unlikely(grp == NULL))
@@ -396,13 +390,7 @@ struct z_erofs_vle_work_finder {
 	*f->hosted = true;
 
 	gnew = true;
-#ifdef CONFIG_EROFS_FS_ZIP_MULTIREF
-skip:
-	/* currently unimplemented */
-	BUG();
-#else
 	work = z_erofs_vle_grab_primary_work(grp);
-#endif
 	work->pageofs = f->pageofs;
 
 	mutex_init(&work->lock);
@@ -797,9 +785,7 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 
 	struct z_erofs_pagevec_ctor ctor;
 	unsigned nr_pages;
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
 	unsigned sparsemem_pages = 0;
-#endif
 	struct page *pages_onstack[Z_EROFS_VLE_VMAP_ONSTACK_PAGES];
 	struct page **pages, **compressed_pages, *page;
 	unsigned i, llen;
@@ -811,11 +797,7 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 	int err;
 
 	might_sleep();
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
 	work = z_erofs_vle_grab_primary_work(grp);
-#else
-	BUG();
-#endif
 	BUG_ON(!READ_ONCE(work->nr_pages));
 
 	mutex_lock(&work->lock);
@@ -866,13 +848,11 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 			pagenr = z_erofs_onlinepage_index(page);
 
 		BUG_ON(pagenr >= nr_pages);
-
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
 		BUG_ON(pages[pagenr] != NULL);
-		++sparsemem_pages;
-#endif
+
 		pages[pagenr] = page;
 	}
+	sparsemem_pages = i;
 
 	z_erofs_pagevec_ctor_exit(&ctor, true);
 
@@ -902,10 +882,8 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 		pagenr = z_erofs_onlinepage_index(page);
 
 		BUG_ON(pagenr >= nr_pages);
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
 		BUG_ON(pages[pagenr] != NULL);
 		++sparsemem_pages;
-#endif
 		pages[pagenr] = page;
 
 		overlapped = true;
@@ -931,12 +909,10 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 	if (err != -ENOTSUPP)
 		goto out_percpu;
 
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
 	if (sparsemem_pages >= nr_pages) {
 		BUG_ON(sparsemem_pages > nr_pages);
 		goto skip_allocpage;
 	}
-#endif
 
 	for (i = 0; i < nr_pages; ++i) {
 		if (pages[i] != NULL)
@@ -945,9 +921,7 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 		pages[i] = __stagingpage_alloc(page_pool, GFP_NOFS);
 	}
 
-#ifndef CONFIG_EROFS_FS_ZIP_MULTIREF
 skip_allocpage:
-#endif
 	vout = erofs_vmap(pages, nr_pages);
 
 	err = z_erofs_vle_unzip_vmap(compressed_pages,
diff --git a/drivers/staging/erofs/unzip_vle.h b/drivers/staging/erofs/unzip_vle.h
index 3939985..3316bc3 100644
--- a/drivers/staging/erofs/unzip_vle.h
+++ b/drivers/staging/erofs/unzip_vle.h
@@ -47,13 +47,6 @@ static inline bool z_erofs_gather_if_stagingpage(struct list_head *page_pool,
 #define Z_EROFS_VLE_INLINE_PAGEVECS     3
 
 struct z_erofs_vle_work {
-	/* struct z_erofs_vle_work *left, *right; */
-
-#ifdef CONFIG_EROFS_FS_ZIP_MULTIREF
-	struct list_head list;
-
-	atomic_t refcount;
-#endif
 	struct mutex lock;
 
 	/* I: decompression offset in page */
@@ -107,10 +100,8 @@ static inline void z_erofs_vle_set_workgrp_fmt(
 	grp->flags = fmt | (grp->flags & ~Z_EROFS_VLE_WORKGRP_FMT_MASK);
 }
 
-#ifdef CONFIG_EROFS_FS_ZIP_MULTIREF
-#error multiref decompression is unimplemented yet
-#else
 
+/* definitions if multiref is disabled */
 #define z_erofs_vle_grab_primary_work(grp)	(&(grp)->work)
 #define z_erofs_vle_grab_work(grp, pageofs)	(&(grp)->work)
 #define z_erofs_vle_work_workgroup(wrk, primary)	\
@@ -118,7 +109,6 @@ static inline void z_erofs_vle_set_workgrp_fmt(
 		struct z_erofs_vle_workgroup, work) : \
 		({ BUG(); (void *)NULL; }))
 
-#endif
 
 #define Z_EROFS_WORKGROUP_SIZE       sizeof(struct z_erofs_vle_workgroup)
 
-- 
1.9.1