Re: [PATCH v10 09/10] erofs: support compressed inodes for page cache share

[Gao Xiang]

On 2025/12/23 09:56, Hongbo Li wrote:

From: Hongzhen Luo <hongz...@linux.alibaba.com>

This patch adds page cache sharing functionality for compressed inodes.

Signed-off-by: Hongzhen Luo <hongz...@linux.alibaba.com>
Signed-off-by: Hongbo Li <lihongb...@huawei.com>
---
  fs/erofs/zdata.c | 42 ++++++++++++++++++++++++++++++++----------
  1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 65da21504632..465918093984 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -493,7 +493,7 @@ 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;

@@ -1883,10 +1883,18 @@ 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));
        int err;

+ if (erofs_is_ishare_inode(inode))

+               realinode = erofs_ishare_iget(inode);
+       else
+               realinode = inode;

I don't think it makes any sense to differ those two cases, just

        struct inode *inode = folio->mapping->host;
        struct inode *realinode = erofs_get_real_inode(inode);
        Z_EROFS_DEFINE_FRONTEND(f, realinode, folio_pos(folio));

...

+
+       if (!realinode)
+               return -EIO;

That is an impossible case, just `DBG_BUGON(!realinode);`

+       f.inode = realinode;
        trace_erofs_read_folio(folio, false);
        z_erofs_pcluster_readmore(&f, NULL, true);
        err = z_erofs_scan_folio(&f, folio, false);
@@ -1896,23 +1904,34 @@ 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_put_real_inode(realinode);

        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));
        unsigned int nrpages = readahead_count(rac);
        struct folio *head = NULL, *folio;
        int err;

- trace_erofs_readahead(inode, readahead_index(rac), nrpages, false);

+       if (erofs_is_ishare_inode(inode))
+               realinode = erofs_ishare_iget(inode);
+       else
+               realinode = inode;
+
+       if (!realinode)
+               return;
+       f.inode = realinode;

Same here.

Thanks,
Gao Xiang