From c20c7992a06434dd4a9624a57aee608acfc33c12 Mon Sep 17 00:00:00 2001
From: gmd20
Date: Tue, 8 Dec 2020 15:27:23 +0800
Subject: main: add "-kernel_cache" flag

This option is similar to fuse(8) kernel_cache

Verified using vmtouch.

Without -kernel_cache:

$ dd if=/dev/zero of=foo bs=1M count=10 ; vmtouch -t foo ; vmtouch foo
10+0 records in
10+0 records out
10485760 bytes (10 MB, 10 MiB) copied, 0,0242321 s, 433 MB/s
           Files: 1
     Directories: 0
   Touched Pages: 2560 (10M)
         Elapsed: 0.011159 seconds
           Files: 1
     Directories: 0
  Resident Pages: 0/2560  0/10M  0%
         Elapsed: 0.000993 seconds

With -kernel_cache:

$ dd if=/dev/zero of=foo bs=1M count=10 ; vmtouch -t foo ; vmtouch foo
10+0 records in
10+0 records out
10485760 bytes (10 MB, 10 MiB) copied, 0,0244015 s, 430 MB/s
           Files: 1
     Directories: 0
   Touched Pages: 2560 (10M)
         Elapsed: 0.011564 seconds
           Files: 1
     Directories: 0
  Resident Pages: 2560/2560  10M/10M  100%
         Elapsed: 0.000369 seconds
---
 internal/fusefrontend/node.go | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'internal/fusefrontend/node.go')

diff --git a/internal/fusefrontend/node.go b/internal/fusefrontend/node.go
index bc4eb3b..80d642c 100644
--- a/internal/fusefrontend/node.go
+++ b/internal/fusefrontend/node.go
@@ -190,6 +190,10 @@ func (n *Node) Open(ctx context.Context, flags uint32) (fh fs.FileHandle, fuseFl
 	rn.openWriteOnlyLock.RLock()
 	defer rn.openWriteOnlyLock.RUnlock()
 
+	if rn.args.KernelCache {
+		fuseFlags = fuse.FOPEN_KEEP_CACHE
+	}
+
 	// Open backing file
 	fd, err := syscallcompat.Openat(dirfd, cName, newFlags, 0)
 	// Handle a few specific errors
-- 
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