linux-kernel - [PATCH v3 11/22] erofs: add anonymous inode managing page cache of blob file

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Date:   Wed,  9 Feb 2022 14:00:57 +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
Subject: [PATCH v3 11/22] 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  | 45 ++++++++++++++++++++++++++++++++++++++++++---
 fs/erofs/internal.h |  3 ++-
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index c043d7709d65..3addd9aa549c 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -6,6 +6,9 @@
 
 static struct fscache_volume *volume;
 
+static const struct address_space_operations erofs_fscache_blob_aops = {
+};
+
 static int erofs_fscache_init_cookie(struct erofs_fscache_context *ctx,
 				     char *path)
 {
@@ -36,8 +39,34 @@ void erofs_fscache_cleanup_cookie(struct erofs_fscache_context *ctx)
 	ctx->cookie = NULL;
 }
 
+static int erofs_fscache_get_inode(struct erofs_fscache_context *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 | __GFP_HIGHMEM | __GFP_MOVABLE);
+	ctx->inode = inode;
+	return 0;
+}
+
+static inline
+void erofs_fscache_put_inode(struct erofs_fscache_context *ctx)
+{
+	iput(ctx->inode);
+	ctx->inode = NULL;
+}
+
 static int erofs_fscache_init_ctx(struct erofs_fscache_context *ctx,
-				  struct super_block *sb, char *path)
+				  struct super_block *sb, char *path,
+				  bool need_inode)
 {
 	int ret;
 
@@ -47,6 +76,15 @@ static int erofs_fscache_init_ctx(struct erofs_fscache_context *ctx,
 		return ret;
 	}
 
+	if (need_inode) {
+		ret = erofs_fscache_get_inode(ctx, sb);
+		if (ret) {
+			erofs_err(sb, "failed to get anonymous inode");
+			erofs_fscache_cleanup_cookie(ctx);
+			return ret;
+		}
+	}
+
 	return 0;
 }
 
@@ -54,10 +92,11 @@ static inline
 void erofs_fscache_cleanup_ctx(struct erofs_fscache_context *ctx)
 {
 	erofs_fscache_cleanup_cookie(ctx);
+	erofs_fscache_put_inode(ctx);
 }
 
 struct erofs_fscache_context *erofs_fscache_get_ctx(struct super_block *sb,
-						char *path)
+						char *path, bool need_inode)
 {
 	struct erofs_fscache_context *ctx;
 	int ret;
@@ -66,7 +105,7 @@ struct erofs_fscache_context *erofs_fscache_get_ctx(struct super_block *sb,
 	if (!ctx)
 		return ERR_PTR(-ENOMEM);
 
-	ret = erofs_fscache_init_ctx(ctx, sb, path);
+	ret = erofs_fscache_init_ctx(ctx, sb, path, need_inode);
 	if (ret) {
 		kfree(ctx);
 		return ERR_PTR(ret);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 1f5bc69e8e9f..bb5e992fe0df 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -99,6 +99,7 @@ struct erofs_sb_lz4_info {
 
 struct erofs_fscache_context {
 	struct fscache_cookie *cookie;
+	struct inode *inode;
 };
 
 struct erofs_sb_info {
@@ -626,7 +627,7 @@ int erofs_init_fscache(void);
 void erofs_exit_fscache(void);
 
 struct erofs_fscache_context *erofs_fscache_get_ctx(struct super_block *sb,
-						char *path);
+						char *path, bool need_inode);
 void erofs_fscache_put_ctx(struct erofs_fscache_context *ctx);
 
 #define EFSCORRUPTED    EUCLEAN         /* Filesystem is corrupted */
-- 
2.27.0