git send-email

git send-email --annotate --compose --to=kcchuang@cs.nctu.edu.tw 0001-bcache-clean-plugout-ed-backing-dev.patch

這樣會把commit額外加在0001-bcache-clean-plugout-ed-backing-dev.patch，而且還不能attach file.

C use O_DIRECT vs O_SYNC => blktrace

1. O_DIRECT
fd = open("/dev/escache0", O_RDWR | O_DIRECT);

blktrace -d /dev/escache0 -o - | blkparse -i -

252,0    4        1     0.000000000 30655  Q  WS 0 + 1 [openescache]

2. O_SYNC

252,0    6        1   129.714324326 30666  Q  WS 0 + 8 [openescache]

252,0    6        2   129.725375608 30666  Q FWS [openescache]

F means 'flush'

openescache.c

#define _GNU_SOURCE

#include <string.h>

#include <stdlib.h>

#include <fcntl.h>

#include <stdio.h>

#define BLOCKSIZE 512

int main() {

    int fd, i;

    void *buffer;

    char image[BLOCKSIZE];

    for(i=0; i<BLOCKSIZE; i++)

        image[i] = 0xa2;

    posix_memalign(&buffer, BLOCKSIZE, BLOCKSIZE);

    memcpy(buffer, image, sizeof(image));

    fd = open("/dev/escache0", O_RDWR | O_SYNC);

    if (fd == -1) {

        printf("open failed");

        return -1;

    }

    write(fd, buffer, BLOCKSIZE);

    close(fd);

    free(buffer);

    return 0;

}

shell script learning

--20180411--
$1:/dev/sdb

for i in $(ls /dev/escache*)
do
        find /sys/block/`echo $i|sed 's/\/dev\///g'`/slaves -name `echo $1|sed 's/\/dev\///g'`
        if [ $? -eq 0 ] ;then
                cache=$(ls /sys/block/`echo $i|sed 's/\/dev\///g'`/slaves |grep -v `echo $1|sed 's/\/dev\///g'`)
                /usr/sbin/bcache-super-show /dev/$cache | grep "cache device"
                if [ $? -eq 0 ] ;then
                        echo 1 > /sys/block/$cache/escache/set/stop
                fi
        fi
done

-- Test --

[' is actually a program, just like ls and other programs, so it must be surrounded by spaces:

keep kernel module symbol table

vim drivers/md/bcache/Makefile:

obj-$(CONFIG_BCACHE)    += escache.o

ccflags-y := -O1

escache-y       := alloc.o bset.o btree.o closure.o debug.o extents.o\
    io.o journal.o movinggc.o request.o stats.o super.o sysfs.o trace.o\
    util.o writeback.o

CFLAGS_request.o    += -Iblock