[PATCH RFC 9/9] cachefiles: cull content map file on cull

[Jingbo Xu <jefflexu@linux.alibaba.com>]

Also hole punch the backing content map file when the backing object
gets culled.

When cacehfilesd is going to cull a whole directory, the whole
directory will be moved to the graveyard and then cacehfilesd itself
will remove all files under the directory one by one. Since each
sub-directory under one volume maintains one backing content map file,
cacehfilesd already works well with this bitmap-based mechanism and
doesn't need any refactoring.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
---
 fs/cachefiles/content-map.c | 37 +++++++++++++++++++++++++++++++++++++
 fs/cachefiles/internal.h    |  4 ++++
 fs/cachefiles/namei.c       |  4 ++++
 fs/cachefiles/xattr.c       | 17 +++++++++++++++++
 4 files changed, 62 insertions(+)

diff --git a/fs/cachefiles/content-map.c b/fs/cachefiles/content-map.c
index 360c59b06670..5584a0182df9 100644
--- a/fs/cachefiles/content-map.c
+++ b/fs/cachefiles/content-map.c
@@ -294,3 +294,40 @@ void cachefiles_shorten_content_map(struct cachefiles_object *object,
 out:
 	read_unlock_bh(&object->content_map_lock);
 }
+
+int cachefiles_cull_content_map(struct cachefiles_cache *cache,
+				struct dentry *dir, struct dentry *victim)
+{
+	struct dentry *map;
+	struct file *map_file;
+	size_t content_map_size = 0;
+	loff_t content_map_off = 0;
+	struct path path;
+	int ret;
+
+	if (!d_is_reg(victim))
+		return 0;
+
+	ret = cachefiles_get_content_info(victim, &content_map_size, &content_map_off);
+	if (ret || !content_map_size)
+		return ret;
+
+	map = lookup_positive_unlocked("Map", dir, strlen("Map"));
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	path.mnt = cache->mnt;
+	path.dentry = map;
+	map_file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE,
+			d_backing_inode(map), cache->cache_cred);
+	if (IS_ERR(map_file)) {
+		dput(map);
+		return PTR_ERR(map_file);
+	}
+
+	ret = vfs_fallocate(map_file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+			      content_map_off, content_map_size);
+
+	fput(map_file);
+	return ret;
+}
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 7747f99f00c1..9c36631ee051 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -190,6 +190,8 @@ extern loff_t cachefiles_find_next_hole(struct cachefiles_object *object,
 extern void cachefiles_invalidate_content_map(struct cachefiles_object *object);
 extern void cachefiles_shorten_content_map(struct cachefiles_object *object,
 					   loff_t new_size);
+extern int cachefiles_cull_content_map(struct cachefiles_cache *cache,
+				struct dentry *dir, struct dentry *victim);
 
 /*
  * daemon.c
@@ -384,6 +386,8 @@ extern int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 extern void cachefiles_prepare_to_write(struct fscache_cookie *cookie);
 extern bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume);
 extern int cachefiles_check_volume_xattr(struct cachefiles_volume *volume);
+extern int cachefiles_get_content_info(struct dentry *dentry,
+		size_t *content_map_size, loff_t *content_map_off);
 
 /*
  * Error handling
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index f5e1ec1d9445..79c759468ab3 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -923,6 +923,10 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
 	if (ret < 0)
 		goto error_unlock;
 
+	ret = cachefiles_cull_content_map(cache, dir, victim);
+	if (ret < 0)
+		goto error;
+
 	ret = cachefiles_bury_object(cache, NULL, dir, victim,
 				     FSCACHE_OBJECT_WAS_CULLED);
 	if (ret < 0)
diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
index 05ac6b70787a..b7091c8e4262 100644
--- a/fs/cachefiles/xattr.c
+++ b/fs/cachefiles/xattr.c
@@ -283,3 +283,20 @@ int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)
 	_leave(" = %d", ret);
 	return ret;
 }
+
+int cachefiles_get_content_info(struct dentry *dentry, size_t *content_map_size,
+				loff_t *content_map_off)
+{
+	struct cachefiles_xattr buf;
+	ssize_t xlen, tlen = sizeof(buf);
+
+	xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, &buf, tlen);
+	if (xlen != tlen)
+		return -ESTALE;
+
+	if (buf.content == CACHEFILES_CONTENT_MAP) {
+		*content_map_off = be64_to_cpu(buf.content_map_off);
+		*content_map_size = be64_to_cpu(buf.content_map_size);
+	}
+	return 0;
+}
-- 
2.27.0