In FUSE, as of now, uncached lookups are expensive over the wire. E.g additional latencies and stressing (meta data) servers from thousands of clients. These lookup calls possibly can be avoided in some cases. Incoming two patches addresses this issue. First patch handles the case where we open first time a file/dir or create a file (O_CREAT) but do a lookup first on it. After lookup is performed we make another call into libfuse to open the file. Now these two separate calls into libfuse can be combined and performed as a single call into libfuse. Second patch handles the case when we are opening an already existing file (positive dentry). Before this open call, we re-validate the inode and this re-validation does a lookup on the file and verify the inode. This separate lookup also can be avoided (for non-dir) and combined with open call into libfuse. Here is the link to the libfuse pull request which implements atomic open https://github.com/libfuse/libfuse/pull/644 I am going to post performance results shortly. Dharmendra Singh (2): FUSE: Implement atomic lookup + open FUSE: Avoid lookup in d_revalidate() fs/fuse/dir.c | 179 +++++++++++++++++++++++++++++++++----- fs/fuse/file.c | 30 ++++++- fs/fuse/fuse_i.h | 13 ++- fs/fuse/inode.c | 4 +- fs/fuse/ioctl.c | 2 +- include/uapi/linux/fuse.h | 2 + 6 files changed, 204 insertions(+), 26 deletions(-) -- 2.17.1
