[Linux-cachefs] [PATCH v6 13/22] erofs: add anonymous inode managing page cache of blob file

[Jeffle Xu]

Introduce one anonymous inode for managing page cache of corresponding
blob file. Then erofs could read directly from the address space of the
anonymous inode when cache hit.

Signed-off-by: Jeffle Xu <jeffl...@linux.alibaba.com>
---
 fs/erofs/fscache.c  | 41 ++++++++++++++++++++++++++++++++++++++++-
 fs/erofs/internal.h |  7 +++++--
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 73235fd43bf6..30383d9adb62 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -7,6 +7,9 @@
 
 static struct fscache_volume *volume;
 
+static const struct address_space_operations erofs_fscache_blob_aops = {
+};
+
 static int erofs_fscache_init_cookie(struct erofs_fscache *ctx, char *path)
 {
        struct fscache_cookie *cookie;
@@ -31,6 +34,29 @@ static inline void erofs_fscache_cleanup_cookie(struct 
erofs_fscache *ctx)
        ctx->cookie = NULL;
 }
 
+static int erofs_fscache_get_inode(struct erofs_fscache *ctx,
+                                  struct super_block *sb)
+{
+       struct inode *const inode = new_inode(sb);
+
+       if (!inode)
+               return -ENOMEM;
+
+       set_nlink(inode, 1);
+       inode->i_size = OFFSET_MAX;
+       inode->i_mapping->a_ops = &erofs_fscache_blob_aops;
+       mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
+
+       ctx->inode = inode;
+       return 0;
+}
+
+static inline void erofs_fscache_put_inode(struct erofs_fscache *ctx)
+{
+       iput(ctx->inode);
+       ctx->inode = NULL;
+}
+
 /*
  * erofs_fscache_get - create an fscache context for blob file
  * @sb:                superblock
@@ -38,7 +64,8 @@ static inline void erofs_fscache_cleanup_cookie(struct 
erofs_fscache *ctx)
  *
  * Return: fscache context on success, ERR_PTR() on failure.
  */
-struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path)
+struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path,
+                                       bool need_inode)
 {
        struct erofs_fscache *ctx;
        int ret;
@@ -53,7 +80,18 @@ struct erofs_fscache *erofs_fscache_get(struct super_block 
*sb, char *path)
                goto err;
        }
 
+       if (need_inode) {
+               ret = erofs_fscache_get_inode(ctx, sb);
+               if (ret) {
+                       erofs_err(sb, "failed to get anonymous inode");
+                       goto err_cookie;
+               }
+       }
+
        return ctx;
+
+err_cookie:
+       erofs_fscache_cleanup_cookie(ctx);
 err:
        kfree(ctx);
        return ERR_PTR(ret);
@@ -65,6 +103,7 @@ void erofs_fscache_put(struct erofs_fscache *ctx)
                return;
 
        erofs_fscache_cleanup_cookie(ctx);
+       erofs_fscache_put_inode(ctx);
        kfree(ctx);
 }
 
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index d4f2b43cedae..459f31803c3b 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -98,6 +98,7 @@ struct erofs_sb_lz4_info {
 
 struct erofs_fscache {
        struct fscache_cookie *cookie;
+       struct inode *inode;
 };
 
 struct erofs_sb_info {
@@ -625,14 +626,16 @@ static inline int z_erofs_load_lzma_config(struct 
super_block *sb,
 int erofs_init_fscache(void);
 void erofs_exit_fscache(void);
 
-struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path);
+struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path,
+                                       bool need_inode);
 void erofs_fscache_put(struct erofs_fscache *ctx);
 #else
 static inline int erofs_init_fscache(void) { return 0; }
 static inline void erofs_exit_fscache(void) {}
 
 static inline struct erofs_fscache *erofs_fscache_get(struct super_block *sb,
-                                                     char *path)
+                                                     char *path,
+                                                     bool need_inode)
 {
        return ERR_PTR(-EOPNOTSUPP);
 }
-- 
2.27.0

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