[RFC PATCH v6 6/7] erofs: support compressed inodes for page cache share

[Hongzhen Luo <hongzhen@linux.alibaba.com>]

This patch adds page cache sharing functionality for compressed inodes.

Signed-off-by: Hongzhen Luo <hongzhen@linux.alibaba.com>
---
 fs/erofs/zdata.c | 57 +++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 47 insertions(+), 10 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index aff09f94afb2..b6383cb26acb 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2022 Alibaba Cloud
  */
 #include "compress.h"
+#include "ishare.h"
 #include <linux/psi.h>
 #include <linux/cpuhotplug.h>
 #include <trace/events/erofs.h>
@@ -474,7 +475,7 @@ enum z_erofs_pclustermode {
 };
 
 struct z_erofs_frontend {
-	struct inode *const inode;
+	struct inode *inode;
 	struct erofs_map_blocks map;
 	struct z_erofs_bvec_iter biter;
 
@@ -1835,11 +1836,24 @@ static void z_erofs_pcluster_readmore(struct z_erofs_frontend *f,
 
 static int z_erofs_read_folio(struct file *file, struct folio *folio)
 {
-	struct inode *const inode = folio->mapping->host;
-	Z_EROFS_DEFINE_FRONTEND(f, inode, folio_pos(folio));
+	struct inode *const inode = folio->mapping->host, *realinode;
+	Z_EROFS_DEFINE_FRONTEND(f, NULL, folio_pos(folio));
+	struct erofs_read_ctx rdctx = {
+		.file = file,
+		.inode = inode,
+	};
 	int err;
 
 	trace_erofs_read_folio(folio, false);
+
+	erofs_read_begin(&rdctx);
+
+	if (erofs_is_ishare_inode(inode))
+		realinode = erofs_ishare_iget(inode);
+	else
+		realinode = inode;
+
+	f.inode = realinode;
 	z_erofs_pcluster_readmore(&f, NULL, true);
 	err = z_erofs_scan_folio(&f, folio, false);
 	z_erofs_pcluster_readmore(&f, NULL, false);
@@ -1848,25 +1862,43 @@ static int z_erofs_read_folio(struct file *file, struct folio *folio)
 	/* if some pclusters are ready, need submit them anyway */
 	err = z_erofs_runqueue(&f, 0) ?: err;
 	if (err && err != -EINTR)
-		erofs_err(inode->i_sb, "read error %d @ %lu of nid %llu",
-			  err, folio->index, EROFS_I(inode)->nid);
+		erofs_err(realinode->i_sb, "read error %d @ %lu of nid %llu",
+			  err, folio->index, EROFS_I(realinode)->nid);
 
 	erofs_put_metabuf(&f.map.buf);
 	erofs_release_pages(&f.pagepool);
+
+	if (erofs_is_ishare_inode(inode))
+		erofs_ishare_iput(realinode);
+
+	erofs_read_end(&rdctx);
+
 	return err;
 }
 
 static void z_erofs_readahead(struct readahead_control *rac)
 {
-	struct inode *const inode = rac->mapping->host;
-	Z_EROFS_DEFINE_FRONTEND(f, inode, readahead_pos(rac));
+	struct inode *const inode = rac->mapping->host, *realinode;
+	Z_EROFS_DEFINE_FRONTEND(f, NULL, readahead_pos(rac));
 	struct folio *head = NULL, *folio;
 	unsigned int nrpages = readahead_count(rac);
+	struct erofs_read_ctx rdctx = {
+		.file = rac->file,
+		.inode = inode,
+	};
 	int err;
 
+	erofs_read_begin(&rdctx);
+
+	if (erofs_is_ishare_inode(inode))
+		realinode = erofs_ishare_iget(inode);
+	else
+		realinode = inode;
+
+	f.inode = realinode;
 	z_erofs_pcluster_readmore(&f, rac, true);
 	nrpages = readahead_count(rac);
-	trace_erofs_readpages(inode, readahead_index(rac), nrpages, false);
+	trace_erofs_readpages(realinode, readahead_index(rac), nrpages, false);
 	while ((folio = readahead_folio(rac))) {
 		folio->private = head;
 		head = folio;
@@ -1879,8 +1911,8 @@ static void z_erofs_readahead(struct readahead_control *rac)
 
 		err = z_erofs_scan_folio(&f, folio, true);
 		if (err && err != -EINTR)
-			erofs_err(inode->i_sb, "readahead error at folio %lu @ nid %llu",
-				  folio->index, EROFS_I(inode)->nid);
+			erofs_err(realinode->i_sb, "readahead error at folio %lu @ nid %llu",
+				  folio->index, EROFS_I(realinode)->nid);
 	}
 	z_erofs_pcluster_readmore(&f, rac, false);
 	z_erofs_pcluster_end(&f);
@@ -1888,6 +1920,11 @@ static void z_erofs_readahead(struct readahead_control *rac)
 	(void)z_erofs_runqueue(&f, nrpages);
 	erofs_put_metabuf(&f.map.buf);
 	erofs_release_pages(&f.pagepool);
+
+	if (erofs_is_ishare_inode(inode))
+		erofs_ishare_iput(realinode);
+
+	erofs_read_end(&rdctx);
 }
 
 const struct address_space_operations z_erofs_aops = {
-- 
2.43.5