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

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Message-Id: <20220325122223.102958-14-jefflexu@linux.alibaba.com>
Date:   Fri, 25 Mar 2022 20:22:14 +0800
From:   Jeffle Xu <jefflexu@...ux.alibaba.com>
To:     dhowells@...hat.com, linux-cachefs@...hat.com, xiang@...nel.org,
        chao@...nel.org, linux-erofs@...ts.ozlabs.org
Cc:     torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
        willy@...radead.org, linux-fsdevel@...r.kernel.org,
        joseph.qi@...ux.alibaba.com, bo.liu@...ux.alibaba.com,
        tao.peng@...ux.alibaba.com, gerry@...ux.alibaba.com,
        eguan@...ux.alibaba.com, linux-kernel@...r.kernel.org,
        luodaowen.backend@...edance.com, tianzichen@...ishou.com,
        fannaihao@...du.com
Subject: [PATCH v6 13/22] erofs: add anonymous inode managing page cache of blob file

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 <jefflexu@...ux.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