linux-kernel - [PATCH v7 11/19] erofs: add anonymous inode managing page cache for data blob

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Date:   Thu, 31 Mar 2022 19:57:45 +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 v7 11/19] erofs: add anonymous inode managing page cache for data blob

Introduce one anonymous inode managing page cache for data blob. 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  | 39 ++++++++++++++++++++++++++++++++++++---
 fs/erofs/internal.h |  6 ++++--
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 67a3c4935245..1c88614203d2 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -5,17 +5,22 @@
 #include <linux/fscache.h>
 #include "internal.h"
 
+static const struct address_space_operations erofs_fscache_meta_aops = {
+};
+
 /*
  * Create an fscache context for data blob.
  * Return: 0 on success and allocated fscache context is assigned to @fscache,
  *	   negative error number on failure.
  */
 int erofs_fscache_register_cookie(struct super_block *sb,
-				  struct erofs_fscache **fscache, char *name)
+				  struct erofs_fscache **fscache,
+				  char *name, bool need_inode)
 {
 	struct fscache_volume *volume = EROFS_SB(sb)->volume;
 	struct erofs_fscache *ctx;
 	struct fscache_cookie *cookie;
+	int ret;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
@@ -25,15 +30,40 @@ int erofs_fscache_register_cookie(struct super_block *sb,
 					name, strlen(name), NULL, 0, 0);
 	if (!cookie) {
 		erofs_err(sb, "failed to get cookie for %s", name);
-		kfree(name);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto err;
 	}
 
 	fscache_use_cookie(cookie, false);
 	ctx->cookie = cookie;
 
+	if (need_inode) {
+		struct inode *const inode = new_inode(sb);
+
+		if (!inode) {
+			erofs_err(sb, "failed to get anon inode for %s", name);
+			ret = -ENOMEM;
+			goto err_cookie;
+		}
+
+		set_nlink(inode, 1);
+		inode->i_size = OFFSET_MAX;
+		inode->i_mapping->a_ops = &erofs_fscache_meta_aops;
+		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
+
+		ctx->inode = inode;
+	}
+
 	*fscache = ctx;
 	return 0;
+
+err_cookie:
+	fscache_unuse_cookie(ctx->cookie, NULL, NULL);
+	fscache_relinquish_cookie(ctx->cookie, false);
+	ctx->cookie = NULL;
+err:
+	kfree(ctx);
+	return ret;
 }
 
 void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
@@ -47,6 +77,9 @@ void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
 	fscache_relinquish_cookie(ctx->cookie, false);
 	ctx->cookie = NULL;
 
+	iput(ctx->inode);
+	ctx->inode = NULL;
+
 	kfree(ctx);
 	*fscache = NULL;
 }
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index c6a3351a4d7d..3a4a344cfed3 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -99,6 +99,7 @@ struct erofs_sb_lz4_info {
 
 struct erofs_fscache {
 	struct fscache_cookie *cookie;
+	struct inode *inode;
 };
 
 struct erofs_sb_info {
@@ -632,7 +633,8 @@ int erofs_fscache_register_fs(struct super_block *sb);
 void erofs_fscache_unregister_fs(struct super_block *sb);
 
 int erofs_fscache_register_cookie(struct super_block *sb,
-				  struct erofs_fscache **fscache, char *name);
+				  struct erofs_fscache **fscache,
+				  char *name, bool need_inode);
 void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache);
 #else
 static inline int erofs_fscache_register_fs(struct super_block *sb) { return 0; }
@@ -640,7 +642,7 @@ static inline void erofs_fscache_unregister_fs(struct super_block *sb) {}
 
 static inline int erofs_fscache_register_cookie(struct super_block *sb,
 						struct erofs_fscache **fscache,
-						char *name)
+						char *name, bool need_inode)
 {
 	return -EOPNOTSUPP;
 }
-- 
2.27.0