）中指向这个打开的文件。打开的文件描述符记录中保存着文件的offset 和 文件status。 每个进程都有个 task_struct 描述符用来描述进程相关的信息，其中有个 files_struct 类型的 files 字段，里面有个保存了当前进程所有已打开文件 描述符的数组，而通过 fd 就可以找到具体的文件描述符:© XXX Page 3 of 23 open & openat 系统调用 by the filesystem. When writeback caching is enabled, the kernel may send read requests even for files opened with O_WRONLY. The filesystem should be prepared to handle this. When writeback caching is FDIRDEntryInfo *dentry, struct fuse_file_info *fi, const FCFSAPIFileContext *fctx) { int result; FCFSAPIFileInfo *fh; ...© XXX Page 15 of 23 fi->fh = (long)fh; return 0; } 整体flags支持方案

file access to the filesystem owner, so that all users (including root) can access the files. allow_root This option is similar to allow_other but file access is limited timestamps (nanoseconds), the mtime and ctime values used * by kernel and filesystem will differ (and result in an apparent * change of times after a cache flush). * * To prevent this problem, this variable effective rights -E, --no-effective print no effective rights -s, --skip-base skip files that only have the base entries -R, --recursive recurse into subdirectories -L, --logical

file structure of virtual block device As mentioned above, CurveBS maps virtual block devices to files. Let's look at the metadata for a file in CurveBS. 1. A file in CurveBS consists of chunks interface based on FUSE. 1. Fs-meta Cluster is used to manage the inode and dentry metadata of files. The architecture is like CurveBS, so metadata scalability is very good in this way. 2. Fs-data

instance on a physical serverCurve metadata organization Curve maps virtual block devices to files Each file contains chunks scattered across storage nodes in the cluster Chunkservers are grouped

cluster, int numCopysets, std::vector* out); 例如要在(zone1 zone2 zone3 zone4)中创建8个copyset: result: cs1 [copyset-1, copyset-7] cs2 [copyset-2, copyset-5] cs3 [copyset-3, copyset-6] cs4 [copyset-1