Hi all, Sorry, ignore this mail. I found that I didn't align the block size when doing direct io... :-(
Regards, Colin ----- Original Message ----- From: "colin" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, August 29, 2005 8:15 PM Subject: A problem about DIRECT IO on ext3 > > Hi all, > I wrote a simple program to test direct io, and found that there are some > strange behaviors of it on "ext3". > My simple program is below. Assume that the executable file name is > "directio". If I do the following: > 1. cp directio aaa > 2. ./directio directio aaa > > The size of aaa is about the same with directio. This is wrong. > It should be 3 times the size of directio because there are 2 write > operations and one lseek to the file end. > > If the second file is not opened with "O_DIRECT", the result is correct. > > What's the problem of direct io? I found that if I remove the instruction of > lseek, the result is correct. > Is there any problem of lseek when doing direct io on ext3? > My platform is 2.6.11. > > Regards, > Colin > > > > > > > > > #define _GNU_SOURCE > > #include <stdio.h> > #include <fcntl.h> > #include <sys/stat.h> > #include <sys/types.h> > #include <stdlib.h> > > > int main(int argc, char **argv) { > > int fd1, fd2, count; > char *ptr1, *ptr2; > > if(argc == 3) { > fd1 = open(argv[1], O_RDONLY | O_DIRECT, S_IRWXU); > fd2 = open(argv[2], O_RDWR | O_CREAT | O_DIRECT); > } else { > printf("Error syntax\n"); > exit(1); > } > printf("%d\n", lseek(fd2, 0, SEEK_END)); > > ptr1 = malloc(4096 + 4096-1); > ptr2 = (void*)((int)ptr1 - (int)ptr1 % 4096 + 4096); > > do { > count = read(fd1, ptr2, 4096); > if(!count) > break; > write(fd2, ptr2, 4096); > write(fd2, ptr2, 4096); > } while(count > 0); > > free(ptr1); > close(fd1); > close(fd2); > } > > > > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
