Re: [PATCH v12 09/10] erofs: support compressed inodes for page cache share

[Gao Xiang]

On 2025/12/31 17:01, 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 | 37 ++++++++++++++++++++++++-------------
  1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 65da21504632..2697c703a4c4 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -493,7 +493,8 @@ enum z_erofs_pclustermode {
  };

struct z_erofs_frontend {

-       struct inode *const inode;
+       struct inode *inode;
+       struct inode *sharedinode;

Let's combine these two lines into one for two related inodes?

        struct inode *inode, *sharedinode;

        struct erofs_map_blocks map;
        struct z_erofs_bvec_iter biter;

@@ -508,8 +509,8 @@ struct z_erofs_frontend {

        unsigned int icur;
  };

-#define Z_EROFS_DEFINE_FRONTEND(fe, i, ho) struct z_erofs_frontend fe = { \

-       .inode = i, .head = Z_EROFS_PCLUSTER_TAIL, \
+#define Z_EROFS_DEFINE_FRONTEND(fe, i, si, ho) struct z_erofs_frontend fe = { \
+       .inode = i, .sharedinode = si, .head = Z_EROFS_PCLUSTER_TAIL, \
        .mode = Z_EROFS_PCLUSTER_FOLLOWED, .headoffset = ho }

static bool z_erofs_should_alloc_cache(struct z_erofs_frontend *fe)

@@ -1866,7 +1867,7 @@ static void z_erofs_pcluster_readmore(struct 
z_erofs_frontend *f,
                pgoff_t index = cur >> PAGE_SHIFT;
                struct folio *folio;

- folio = erofs_grab_folio_nowait(inode->i_mapping, index);

+               folio = erofs_grab_folio_nowait(f->sharedinode->i_mapping, 
index);
                if (!IS_ERR_OR_NULL(folio)) {
                        if (folio_test_uptodate(folio))
                                folio_unlock(folio);
@@ -1883,8 +1884,10 @@ 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 sharedinode = folio->mapping->host;

Let's drop useless const annotation:

        struct inode *sharedinode = folio->mapping->host;

+       bool need_iput;
+       struct inode *realinode = erofs_real_inode(sharedinode, &need_iput);
+       Z_EROFS_DEFINE_FRONTEND(f, realinode, sharedinode, folio_pos(folio));
        int err;

trace_erofs_read_folio(folio, false);

@@ -1896,23 +1899,28 @@ 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 (need_iput)
+               iput(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 sharedinode = rac->mapping->host;

Same here.
        struct inode *sharedinode = rac->mapping->host;

Thanks,
Gao Xiang