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    Subject[PATCH v3 0/3] FUSE: Implement atomic lookup + open/create
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    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 three patches address this issue.


    Fist patch handles the case where we are creating a file with O_CREAT.
    Before we go for file creation, we do a lookup on the file which is most
    likely non-existent. After this lookup is done, we again go into libfuse
    to create file. Such lookups where file is most likely non-existent, can
    be avoided.

    Second patch handles the case where we open first time a file/dir
    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.

    Third 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. After open returns we can revalidate the inode.
    This optimisation is performed only when we do not have default permissions
    enabled.

    Here is the link to performance numbers
    https://lore.kernel.org/linux-fsdevel/20220322121212.5087-1-dharamhans87@gmail.com/

    Dharmendra Singh (3):
    FUSE: Implement atomic lookup + create
    Implement atomic lookup + open
    Avoid lookup in d_revalidate()

    fs/fuse/dir.c | 210 +++++++++++++++++++++++++++++++++++---
    fs/fuse/file.c | 30 +++++-
    fs/fuse/fuse_i.h | 16 ++-
    fs/fuse/inode.c | 4 +-
    fs/fuse/ioctl.c | 2 +-
    include/uapi/linux/fuse.h | 5 +
    6 files changed, 245 insertions(+), 22 deletions(-)

    --
    2.17.1

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