fuse: enable caching of symlinks

FUSE file reads are cached in the page cache, but symlink reads are
not. This patch enables FUSE READLINK operations to be cached which
can improve performance of some FUSE workloads.

In particular, I'm working on a FUSE filesystem for access to source
code and discovered that about a 10% improvement to build times is
achieved with this patch (there are a lot of symlinks in the source
tree).

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 76f46f159992..b4967d48bfda 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -121,6 +121,7 @@
  *  - add FUSE_COPY_FILE_RANGE
  *  - add FOPEN_CACHE_DIR
  *  - add FUSE_MAX_PAGES, add max_pages to init_out
+ *  - add FUSE_CACHE_SYMLINKS
  */
 
 #ifndef _LINUX_FUSE_H
@@ -257,6 +258,7 @@ struct fuse_file_lock {
  * FUSE_POSIX_ACL: filesystem supports posix acls
  * FUSE_ABORT_ERROR: reading the device after abort returns ECONNABORTED
  * FUSE_MAX_PAGES: init_out.max_pages contains the max number of req pages
+ * FUSE_CACHE_SYMLINKS: cache READLINK responses
  */
 #define FUSE_ASYNC_READ         (1 << 0)
 #define FUSE_POSIX_LOCKS        (1 << 1)
@@ -281,6 +283,7 @@ struct fuse_file_lock {
 #define FUSE_POSIX_ACL          (1 << 20)
 #define FUSE_ABORT_ERROR        (1 << 21)
 #define FUSE_MAX_PAGES          (1 << 22)
+#define FUSE_CACHE_SYMLINKS     (1 << 23)
 
 /**
  * CUSE INIT request/reply flags