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

[Hongzhen Luo]

This patch adds page cache sharing functionality for compressed inodes.

Signed-off-by: Hongzhen Luo <hongz...@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