import(life): Add operating system course design.

6 files changed, 273 insertions, 0 deletions

diff --git a/works/life/operating-system-course-design/0001-crupesteam-fat-patch.patch b/works/life/operating-system-course-design/0001-crupesteam-fat-patch.patch
new file mode 100644
index 0000000..9f23ebb
--- /dev/null
+++ b/works/life/operating-system-course-design/0001-crupesteam-fat-patch.patch
@@ -0,0 +1,163 @@
+From e88345bbb9a4027033254933ee2e1cad9feab6d6 Mon Sep 17 00:00:00 2001
+From: crupest <crupest@outlook.com>
+Date: Thu, 24 Jun 2021 16:00:04 +0800
+Subject: [PATCH] crupesteam fat patch.
+
+---
+ fs/fat/cache.c | 64 ++++++++++++++++++++++++++++++++++++++++++++------
+ 1 file changed, 57 insertions(+), 7 deletions(-)
+
+diff --git a/fs/fat/cache.c b/fs/fat/cache.c
+index 738e427e2d21..4f32bfee6d27 100644
+--- a/fs/fat/cache.c
++++ b/fs/fat/cache.c
+@@ -15,11 +15,15 @@
+ /* this must be > 0. */
+ #define FAT_MAX_CACHE	8
+ 
++#define FAT_CACHE_PREV_CLUSTER_COUNT 8
++
+ struct fat_cache {
+ 	struct list_head cache_list;
+ 	int nr_contig;	/* number of contiguous clusters */
+ 	int fcluster;	/* cluster number in the file. */
+ 	int dcluster;	/* cluster number on disk. */
++	int prev_clusters_count;
++	int prev_clusters[FAT_CACHE_PREV_CLUSTER_COUNT];
+ };
+ 
+ struct fat_cache_id {
+@@ -27,6 +31,8 @@ struct fat_cache_id {
+ 	int nr_contig;
+ 	int fcluster;
+ 	int dcluster;
++	int prev_clusters_count;
++	int prev_clusters[FAT_CACHE_PREV_CLUSTER_COUNT];
+ };
+ 
+ static inline int fat_max_cache(struct inode *inode)
+@@ -84,10 +90,17 @@ static int fat_cache_lookup(struct inode *inode, int fclus,
+ 	static struct fat_cache nohit = { .fcluster = 0, };
+ 
+ 	struct fat_cache *hit = &nohit, *p;
+-	int offset = -1;
++	int offset = INT_MIN;
+ 
+ 	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+ 	list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
++		if (p->fcluster > fclus &&
++			p->fcluster - p->prev_clusters_count <= fclus) {
++				hit = p;
++				offset = fclus - hit->fcluster;
++				break;
++		}
++
+ 		/* Find the cache of "fclus" or nearest cache. */
+ 		if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
+ 			hit = p;
+@@ -107,7 +120,11 @@ static int fat_cache_lookup(struct inode *inode, int fclus,
+ 		cid->fcluster = hit->fcluster;
+ 		cid->dcluster = hit->dcluster;
+ 		*cached_fclus = cid->fcluster + offset;
+-		*cached_dclus = cid->dcluster + offset;
++
++		if (offset < 0)
++			*cached_dclus = hit->prev_clusters[hit->prev_clusters_count + offset];
++		else
++			*cached_dclus = cid->dcluster + offset;
+ 	}
+ 	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+ 
+@@ -145,6 +162,8 @@ static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
+ 
+ 	cache = fat_cache_merge(inode, new);
+ 	if (cache == NULL) {
++		int i;
++
+ 		if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
+ 			MSDOS_I(inode)->nr_caches++;
+ 			spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+@@ -172,6 +191,10 @@ static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
+ 		cache->fcluster = new->fcluster;
+ 		cache->dcluster = new->dcluster;
+ 		cache->nr_contig = new->nr_contig;
++		cache->prev_clusters_count = new->prev_clusters_count;
++		for (i = 0; i < new->prev_clusters_count; i++) {
++			cache->prev_clusters[i] = new->prev_clusters[i];
++		}
+ 	}
+ out_update_lru:
+ 	fat_cache_update_lru(inode, cache);
+@@ -220,6 +243,7 @@ static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
+ 	cid->fcluster = fclus;
+ 	cid->dcluster = dclus;
+ 	cid->nr_contig = 0;
++	cid->prev_clusters_count = 0;
+ }
+ 
+ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
+@@ -230,6 +254,10 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
+ 	struct fat_entry fatent;
+ 	struct fat_cache_id cid;
+ 	int nr;
++	int offset;
++	int prev_cluster[FAT_CACHE_PREV_CLUSTER_COUNT];
++	int prev_cluster_current = 0;
++	int prev_cluster_count = 0;
+ 
+ 	BUG_ON(MSDOS_I(inode)->i_start == 0);
+ 
+@@ -244,12 +272,13 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
+ 	if (cluster == 0)
+ 		return 0;
+ 
+-	if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
+-		/*
+-		 * dummy, always not contiguous
+-		 * This is reinitialized by cache_init(), later.
+-		 */
++	offset = fat_cache_lookup(inode, cluster, &cid, fclus, dclus);
++
++	if (offset == INT_MIN) {
+ 		cache_init(&cid, -1, -1);
++	} else if (offset < 0) {
++		nr = 0;
++		goto out;
+ 	}
+ 
+ 	fatent_init(&fatent);
+@@ -278,10 +307,31 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
+ 		}
+ 		(*fclus)++;
+ 		*dclus = nr;
++
++		prev_cluster[prev_cluster_current++] = *dclus;
++		if (prev_cluster_count < FAT_CACHE_PREV_CLUSTER_COUNT) {
++			prev_cluster_count++;
++		}
++		prev_cluster_current %= FAT_CACHE_PREV_CLUSTER_COUNT;
++
+ 		if (!cache_contiguous(&cid, *dclus))
+ 			cache_init(&cid, *fclus, *dclus);
+ 	}
+ 	nr = 0;
++
++	if (cid.nr_contig + 1 < FAT_CACHE_PREV_CLUSTER_COUNT) {
++		int i;
++		int count = prev_cluster_count - cid.nr_contig - 1;
++		int start = ((prev_cluster_current - prev_cluster_count)
++			+ FAT_CACHE_PREV_CLUSTER_COUNT) % FAT_CACHE_PREV_CLUSTER_COUNT; 
++
++		cid.prev_clusters_count = count;
++
++		for (i = 0; i < count; i++) {
++			cid.prev_clusters[i] = prev_cluster[(start + i) % FAT_CACHE_PREV_CLUSTER_COUNT];
++		}
++	}
++
+ 	fat_cache_add(inode, &cid);
+ out:
+ 	fatent_brelse(&fatent);
+-- 
+2.32.0
+
diff --git a/works/life/operating-system-course-design/Vagrantfile b/works/life/operating-system-course-design/Vagrantfile
new file mode 100644
index 0000000..8f4509f
--- /dev/null
+++ b/works/life/operating-system-course-design/Vagrantfile
@@ -0,0 +1,72 @@
+# -*- mode: ruby -*-

+# vi: set ft=ruby :

+

+# All Vagrant configuration is done below. The "2" in Vagrant.configure

+# configures the configuration version (we support older styles for

+# backwards compatibility). Please don't change it unless you know what

+# you're doing.

+Vagrant.configure("2") do |config|

+  # The most common configuration options are documented and commented below.

+  # For a complete reference, please see the online documentation at

+  # https://docs.vagrantup.com.

+

+  # Every Vagrant development environment requires a box. You can search for

+  # boxes at https://vagrantcloud.com/search.

+  config.vm.box = "archlinux/archlinux"

+

+  config.vm.disk :disk, size: "10GB", name: "fat_test"

+

+  # Disable automatic box update checking. If you disable this, then

+  # boxes will only be checked for updates when the user runs

+  # `vagrant box outdated`. This is not recommended.

+  # config.vm.box_check_update = false

+

+  # Create a forwarded port mapping which allows access to a specific port

+  # within the machine from a port on the host machine. In the example below,

+  # accessing "localhost:8080" will access port 80 on the guest machine.

+  # NOTE: This will enable public access to the opened port

+  # config.vm.network "forwarded_port", guest: 80, host: 8080

+

+  # Create a forwarded port mapping which allows access to a specific port

+  # within the machine from a port on the host machine and only allow access

+  # via 127.0.0.1 to disable public access

+  # config.vm.network "forwarded_port", guest: 80, host: 8080, host_ip: "127.0.0.1"

+

+  # Create a private network, which allows host-only access to the machine

+  # using a specific IP.

+  # config.vm.network "private_network", ip: "192.168.33.10"

+

+  # Create a public network, which generally matched to bridged network.

+  # Bridged networks make the machine appear as another physical device on

+  # your network.

+  # config.vm.network "public_network"

+

+  # Share an additional folder to the guest VM. The first argument is

+  # the path on the host to the actual folder. The second argument is

+  # the path on the guest to mount the folder. And the optional third

+  # argument is a set of non-required options.

+  # config.vm.synced_folder "../data", "/vagrant_data"

+

+  # Provider-specific configuration so you can fine-tune various

+  # backing providers for Vagrant. These expose provider-specific options.

+  # Example for VirtualBox:

+  #

+  # config.vm.provider "virtualbox" do |vb|

+  #   # Display the VirtualBox GUI when booting the machine

+  #   vb.gui = true

+  #

+  #   # Customize the amount of memory on the VM:

+  #   vb.memory = "1024"

+  # end

+  #

+  # View the documentation for the provider you are using for more

+  # information on available options.

+

+  # Enable provisioning with a shell script. Additional provisioners such as

+  # Ansible, Chef, Docker, Puppet and Salt are also available. Please see the

+  # documentation for more information about their specific syntax and use.

+  # config.vm.provision "shell", inline: <<-SHELL

+  #   apt-get update

+  #   apt-get install -y apache2

+  # SHELL

+end

diff --git a/works/life/operating-system-course-design/create-file.bash b/works/life/operating-system-course-design/create-file.bash
new file mode 100644
index 0000000..d9afec2
--- /dev/null
+++ b/works/life/operating-system-course-design/create-file.bash
@@ -0,0 +1,13 @@
+let file_count=2*1024*2;
+
+for iter in `seq $file_count`; do
+    truncate -s 512KB /mnt/fat-test/$iter;
+done
+
+for iter in `seq $file_count`; do
+    if (($iter % 2 == 0)); then
+        rm /mnt/fat-test/$iter;
+    fi
+done
+
+truncate -s 500MB /mnt/fat-test/big;
diff --git a/works/life/operating-system-course-design/read-file.c b/works/life/operating-system-course-design/read-file.c
new file mode 100644
index 0000000..fe71f94
--- /dev/null
+++ b/works/life/operating-system-course-design/read-file.c
@@ -0,0 +1,25 @@
+#include <bits/types.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdio.h>
+
+int main() {
+  int fd = open("/mnt/fat-test/big", O_RDONLY);
+  if (fd < 0)
+    return 1;
+
+  __off_t size = lseek(fd, 0, SEEK_END);
+  if (size < 0)
+    return 2;
+
+  for (__off_t i = 512; i <= size; i += 512) {
+    if (lseek(fd, size - i, SEEK_SET) < 0)
+      return 3;
+    char buffer[512];
+    if (read(fd, buffer, 512) < 0)
+      return 4;
+  }
+
+  return 0;
+}
diff --git a/works/life/operating-system-course-design/魔改前.png b/works/life/operating-system-course-design/魔改前.png
new file mode 100644
index 0000000..8cc7c8c
--- /dev/null
+++ b/works/life/operating-system-course-design/魔改前.png
diff --git a/works/life/operating-system-course-design/魔改后.png b/works/life/operating-system-course-design/魔改后.png
new file mode 100644
index 0000000..6c4fc70
--- /dev/null
+++ b/works/life/operating-system-course-design/魔改后.png