erofs: tidy up zdata.c

All small code style adjustments, no logic changes:

 - z_erofs_decompress_frontend => z_erofs_frontend;
 - z_erofs_decompress_backend => z_erofs_backend;
 - Use Z_EROFS_DEFINE_FRONTEND() to replace DECOMPRESS_FRONTEND_INIT();
 - `nr_folios` should be `nrpages` in z_erofs_readahead();
 - Refine in-line comments.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250114034429.431408-3-hsiangkao@linux.alibaba.com

1 files changed, 43 insertions, 68 deletions

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 057d68eaa5d2..72c1d5d27c3a 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -455,31 +455,25 @@ err_decompressor:
 }
 
 enum z_erofs_pclustermode {
+	/* It has previously been linked into another processing chain */
 	Z_EROFS_PCLUSTER_INFLIGHT,
 	/*
-	 * a weak form of Z_EROFS_PCLUSTER_FOLLOWED, the difference is that it
-	 * could be dispatched into bypass queue later due to uptodated managed
-	 * pages. All related online pages cannot be reused for inplace I/O (or
-	 * bvpage) since it can be directly decoded without I/O submission.
+	 * A weaker form of Z_EROFS_PCLUSTER_FOLLOWED; the difference is that it
+	 * may be dispatched to the bypass queue later due to uptodated managed
+	 * folios.  All file-backed folios related to this pcluster cannot be
+	 * reused for in-place I/O (or bvpage) since the pcluster may be decoded
+	 * in a separate queue (and thus out of order).
 	 */
 	Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE,
 	/*
-	 * The pcluster was just linked to a decompression chain by us.  It can
-	 * also be linked with the remaining pclusters, which means if the
-	 * processing page is the tail page of a pcluster, this pcluster can
-	 * safely use the whole page (since the previous pcluster is within the
-	 * same chain) for in-place I/O, as illustrated below:
-	 *  ___________________________________________________
-	 * |  tail (partial) page  |    head (partial) page    |
-	 * |  (of the current pcl) |   (of the previous pcl)   |
-	 * |___PCLUSTER_FOLLOWED___|_____PCLUSTER_FOLLOWED_____|
-	 *
-	 * [  (*) the page above can be used as inplace I/O.   ]
+	 * The pcluster has just been linked to our processing chain.
+	 * File-backed folios (except for the head page) related to it can be
+	 * used for in-place I/O (or bvpage).
 	 */
 	Z_EROFS_PCLUSTER_FOLLOWED,
 };
 
-struct z_erofs_decompress_frontend {
+struct z_erofs_frontend {
 	struct inode *const inode;
 	struct erofs_map_blocks map;
 	struct z_erofs_bvec_iter biter;
@@ -495,11 +489,11 @@ struct z_erofs_decompress_frontend {
 	unsigned int icur;
 };
 
-#define DECOMPRESS_FRONTEND_INIT(__i) { \
-	.inode = __i, .head = Z_EROFS_PCLUSTER_TAIL, \
-	.mode = Z_EROFS_PCLUSTER_FOLLOWED }
+#define Z_EROFS_DEFINE_FRONTEND(fe, i, ho) struct z_erofs_frontend fe = { \
+	.inode = i, .head = Z_EROFS_PCLUSTER_TAIL, \
+	.mode = Z_EROFS_PCLUSTER_FOLLOWED, .headoffset = ho }
 
-static bool z_erofs_should_alloc_cache(struct z_erofs_decompress_frontend *fe)
+static bool z_erofs_should_alloc_cache(struct z_erofs_frontend *fe)
 {
 	unsigned int cachestrategy = EROFS_I_SB(fe->inode)->opt.cache_strategy;
 
@@ -516,7 +510,7 @@ static bool z_erofs_should_alloc_cache(struct z_erofs_decompress_frontend *fe)
 	return false;
 }
 
-static void z_erofs_bind_cache(struct z_erofs_decompress_frontend *fe)
+static void z_erofs_bind_cache(struct z_erofs_frontend *fe)
 {
 	struct address_space *mc = MNGD_MAPPING(EROFS_I_SB(fe->inode));
 	struct z_erofs_pcluster *pcl = fe->pcl;
@@ -673,7 +667,7 @@ int erofs_init_managed_cache(struct super_block *sb)
 }
 
 /* callers must be with pcluster lock held */
-static int z_erofs_attach_page(struct z_erofs_decompress_frontend *fe,
+static int z_erofs_attach_page(struct z_erofs_frontend *fe,
 			       struct z_erofs_bvec *bvec, bool exclusive)
 {
 	struct z_erofs_pcluster *pcl = fe->pcl;
@@ -719,7 +713,7 @@ static bool z_erofs_get_pcluster(struct z_erofs_pcluster *pcl)
 	return true;
 }
 
-static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
+static int z_erofs_register_pcluster(struct z_erofs_frontend *fe)
 {
 	struct erofs_map_blocks *map = &fe->map;
 	struct super_block *sb = fe->inode->i_sb;
@@ -789,7 +783,7 @@ err_out:
 	return err;
 }
 
-static int z_erofs_pcluster_begin(struct z_erofs_decompress_frontend *fe)
+static int z_erofs_pcluster_begin(struct z_erofs_frontend *fe)
 {
 	struct erofs_map_blocks *map = &fe->map;
 	struct super_block *sb = fe->inode->i_sb;
@@ -862,14 +856,9 @@ static int z_erofs_pcluster_begin(struct z_erofs_decompress_frontend *fe)
 	return 0;
 }
 
-/*
- * keep in mind that no referenced pclusters will be freed
- * only after a RCU grace period.
- */
 static void z_erofs_rcu_callback(struct rcu_head *head)
 {
-	z_erofs_free_pcluster(container_of(head,
-			struct z_erofs_pcluster, rcu));
+	z_erofs_free_pcluster(container_of(head, struct z_erofs_pcluster, rcu));
 }
 
 static bool __erofs_try_to_release_pcluster(struct erofs_sb_info *sbi,
@@ -911,8 +900,7 @@ static bool erofs_try_to_release_pcluster(struct erofs_sb_info *sbi,
 	return free;
 }
 
-unsigned long z_erofs_shrink_scan(struct erofs_sb_info *sbi,
-				  unsigned long nr_shrink)
+unsigned long z_erofs_shrink_scan(struct erofs_sb_info *sbi, unsigned long nr)
 {
 	struct z_erofs_pcluster *pcl;
 	unsigned long index, freed = 0;
@@ -925,7 +913,7 @@ unsigned long z_erofs_shrink_scan(struct erofs_sb_info *sbi,
 		xa_unlock(&sbi->managed_pslots);
 
 		++freed;
-		if (!--nr_shrink)
+		if (!--nr)
 			return freed;
 		xa_lock(&sbi->managed_pslots);
 	}
@@ -954,7 +942,7 @@ static void z_erofs_put_pcluster(struct erofs_sb_info *sbi,
 		call_rcu(&pcl->rcu, z_erofs_rcu_callback);
 }
 
-static void z_erofs_pcluster_end(struct z_erofs_decompress_frontend *fe)
+static void z_erofs_pcluster_end(struct z_erofs_frontend *fe)
 {
 	struct z_erofs_pcluster *pcl = fe->pcl;
 
@@ -967,13 +955,9 @@ static void z_erofs_pcluster_end(struct z_erofs_decompress_frontend *fe)
 	if (fe->candidate_bvpage)
 		fe->candidate_bvpage = NULL;
 
-	/*
-	 * if all pending pages are added, don't hold its reference
-	 * any longer if the pcluster isn't hosted by ourselves.
-	 */
+	/* Drop refcount if it doesn't belong to our processing chain */
 	if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE)
 		z_erofs_put_pcluster(EROFS_I_SB(fe->inode), pcl, false);
-
 	fe->pcl = NULL;
 }
 
@@ -1002,7 +986,7 @@ static int z_erofs_read_fragment(struct super_block *sb, struct folio *folio,
 	return 0;
 }
 
-static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f,
+static int z_erofs_scan_folio(struct z_erofs_frontend *f,
 			      struct folio *folio, bool ra)
 {
 	struct inode *const inode = f->inode;
@@ -1117,7 +1101,7 @@ static bool z_erofs_page_is_invalidated(struct page *page)
 	return !page_folio(page)->mapping && !z_erofs_is_shortlived_page(page);
 }
 
-struct z_erofs_decompress_backend {
+struct z_erofs_backend {
 	struct page *onstack_pages[Z_EROFS_ONSTACK_PAGES];
 	struct super_block *sb;
 	struct z_erofs_pcluster *pcl;
@@ -1137,7 +1121,7 @@ struct z_erofs_bvec_item {
 	struct list_head list;
 };
 
-static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
+static void z_erofs_do_decompressed_bvec(struct z_erofs_backend *be,
 					 struct z_erofs_bvec *bvec)
 {
 	struct z_erofs_bvec_item *item;
@@ -1160,8 +1144,7 @@ static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
 	list_add(&item->list, &be->decompressed_secondary_bvecs);
 }
 
-static void z_erofs_fill_other_copies(struct z_erofs_decompress_backend *be,
-				      int err)
+static void z_erofs_fill_other_copies(struct z_erofs_backend *be, int err)
 {
 	unsigned int off0 = be->pcl->pageofs_out;
 	struct list_head *p, *n;
@@ -1202,7 +1185,7 @@ static void z_erofs_fill_other_copies(struct z_erofs_decompress_backend *be,
 	}
 }
 
-static void z_erofs_parse_out_bvecs(struct z_erofs_decompress_backend *be)
+static void z_erofs_parse_out_bvecs(struct z_erofs_backend *be)
 {
 	struct z_erofs_pcluster *pcl = be->pcl;
 	struct z_erofs_bvec_iter biter;
@@ -1227,8 +1210,7 @@ static void z_erofs_parse_out_bvecs(struct z_erofs_decompress_backend *be)
 		z_erofs_put_shortlivedpage(be->pagepool, old_bvpage);
 }
 
-static int z_erofs_parse_in_bvecs(struct z_erofs_decompress_backend *be,
-				  bool *overlapped)
+static int z_erofs_parse_in_bvecs(struct z_erofs_backend *be, bool *overlapped)
 {
 	struct z_erofs_pcluster *pcl = be->pcl;
 	unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
@@ -1263,8 +1245,7 @@ static int z_erofs_parse_in_bvecs(struct z_erofs_decompress_backend *be,
 	return err;
 }
 
-static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
-				       int err)
+static int z_erofs_decompress_pcluster(struct z_erofs_backend *be, int err)
 {
 	struct erofs_sb_info *const sbi = EROFS_SB(be->sb);
 	struct z_erofs_pcluster *pcl = be->pcl;
@@ -1394,7 +1375,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
 static int z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
 				    struct page **pagepool)
 {
-	struct z_erofs_decompress_backend be = {
+	struct z_erofs_backend be = {
 		.sb = io->sb,
 		.pagepool = pagepool,
 		.decompressed_secondary_bvecs =
@@ -1472,7 +1453,7 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 }
 
 static void z_erofs_fill_bio_vec(struct bio_vec *bvec,
-				 struct z_erofs_decompress_frontend *f,
+				 struct z_erofs_frontend *f,
 				 struct z_erofs_pcluster *pcl,
 				 unsigned int nr,
 				 struct address_space *mc)
@@ -1651,7 +1632,7 @@ static void z_erofs_endio(struct bio *bio)
 		bio_put(bio);
 }
 
-static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
+static void z_erofs_submit_queue(struct z_erofs_frontend *f,
 				 struct z_erofs_decompressqueue *fgq,
 				 bool *force_fg, bool readahead)
 {
@@ -1784,17 +1765,16 @@ drain_io:
 	z_erofs_decompress_kickoff(q[JQ_SUBMIT], nr_bios);
 }
 
-static int z_erofs_runqueue(struct z_erofs_decompress_frontend *f,
-			    unsigned int ra_folios)
+static int z_erofs_runqueue(struct z_erofs_frontend *f, unsigned int rapages)
 {
 	struct z_erofs_decompressqueue io[NR_JOBQUEUES];
 	struct erofs_sb_info *sbi = EROFS_I_SB(f->inode);
-	bool force_fg = z_erofs_is_sync_decompress(sbi, ra_folios);
+	bool force_fg = z_erofs_is_sync_decompress(sbi, rapages);
 	int err;
 
 	if (f->head == Z_EROFS_PCLUSTER_TAIL)
 		return 0;
-	z_erofs_submit_queue(f, io, &force_fg, !!ra_folios);
+	z_erofs_submit_queue(f, io, &force_fg, !!rapages);
 
 	/* handle bypass queue (no i/o pclusters) immediately */
 	err = z_erofs_decompress_queue(&io[JQ_BYPASS], &f->pagepool);
@@ -1812,7 +1792,7 @@ static int z_erofs_runqueue(struct z_erofs_decompress_frontend *f,
  * Since partial uptodate is still unimplemented for now, we have to use
  * approximate readmore strategies as a start.
  */
-static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
+static void z_erofs_pcluster_readmore(struct z_erofs_frontend *f,
 		struct readahead_control *rac, bool backmost)
 {
 	struct inode *inode = f->inode;
@@ -1867,12 +1847,10 @@ static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
 static int z_erofs_read_folio(struct file *file, struct folio *folio)
 {
 	struct inode *const inode = folio->mapping->host;
-	struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
+	Z_EROFS_DEFINE_FRONTEND(f, inode, folio_pos(folio));
 	int err;
 
 	trace_erofs_read_folio(folio, false);
-	f.headoffset = (erofs_off_t)folio->index << PAGE_SHIFT;
-
 	z_erofs_pcluster_readmore(&f, NULL, true);
 	err = z_erofs_scan_folio(&f, folio, false);
 	z_erofs_pcluster_readmore(&f, NULL, false);
@@ -1892,17 +1870,14 @@ static int z_erofs_read_folio(struct file *file, struct folio *folio)
 static void z_erofs_readahead(struct readahead_control *rac)
 {
 	struct inode *const inode = rac->mapping->host;
-	struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
+	Z_EROFS_DEFINE_FRONTEND(f, inode, readahead_pos(rac));
 	struct folio *head = NULL, *folio;
-	unsigned int nr_folios;
+	unsigned int nrpages = readahead_count(rac);
 	int err;
 
-	f.headoffset = readahead_pos(rac);
-
 	z_erofs_pcluster_readmore(&f, rac, true);
-	nr_folios = readahead_count(rac);
-	trace_erofs_readpages(inode, readahead_index(rac), nr_folios, false);
-
+	nrpages = readahead_count(rac);
+	trace_erofs_readpages(inode, readahead_index(rac), nrpages, false);
 	while ((folio = readahead_folio(rac))) {
 		folio->private = head;
 		head = folio;
@@ -1921,7 +1896,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
 	z_erofs_pcluster_readmore(&f, rac, false);
 	z_erofs_pcluster_end(&f);
 
-	(void)z_erofs_runqueue(&f, nr_folios);
+	(void)z_erofs_runqueue(&f, nrpages);
 	erofs_put_metabuf(&f.map.buf);
 	erofs_release_pages(&f.pagepool);
 }