Messages in this thread |  | | Date | Mon, 3 Sep 2001 15:13:42 -0500 | From | Bob McElrath <> | Subject | using O_DIRECT |
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I have written a small program to use O_DIRECT (attached), after applying your patch o_direct-14 to kernel 2.4.9. Opening the file with O_DIRECT is successful, but attempts to write to the fd return EINVAL.
Am I doing something wrong? Should I have to recompile glibc too?
(0)<root@draal:/usr/src/mjpeg_play> gcc -o testopen testopen.c (0)<root@draal:/usr/src/mjpeg_play> strace ./testopen > /dev/null execve("./testopen", ["./testopen"], [/* 54 vars */]) = 0 uname({sys="Linux", node="draal.physics.wisc.edu", ...}) = 0 brk(0) = 0x120010d90 open("/etc/ld.so.preload", O_RDONLY) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=62527, ...}) = 0 mmap(NULL, 62527, PROT_READ, MAP_PRIVATE, 3, 0) = 0x20000030000 close(3) = 0 open("/lib/libc.so.6.1", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0&\220\1\0\0\0`\201\3"..., 1024) = 1024 fstat(3, {st_mode=S_IFREG|0755, st_size=9653762, ...}) = 0 mmap(NULL, 1558648, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x20000040000 mprotect(0x2000019a000, 141432, PROT_NONE) = 0 mmap(0x200001a0000, 98304, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0x150000) = 0x200001a0000 mmap(0x200001b8000, 18552, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x200001b8000 close(3) = 0 munmap(0x20000030000, 62527) = 0 getxpid() = 2387 open("testopen.txt", O_RDWR|O_CREAT|O_SYNC|0x100000, 0644) = 3 fstat(1, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 3), ...}) = 0 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2000001e000 ioctl(1, TCGETS, 0x11fffea50) = -1 ENOTTY (Inappropriate ioctl for device) write(3, "Welcome to the winter of my disc"..., 40) = -1 EINVAL (Invalid argument) close(3) = 0 write(1, "Got fd 3.\nUnable to write to fil"..., 77) = 77 munmap(0x2000001e000, 8192) = 0 exit(0) = ?
Cheers, -- Bob
Bob McElrath (rsmcelrath@students.wisc.edu) Univ. of Wisconsin at Madison, Department of Physics /* Test opening of a file with O_DIRECT */
#include <asm/types.h> #include <sys/types.h> #include <sys/stat.h> #include <linux/types.h> #include <asm/fcntl.h> /* Note: <fcntl.h> DOES NOT HAVE O_DIRECT! */ /* <fcntl.h> is a glibc header... */ #include <errno.h> #include <stdio.h>
int main(void) { char message[] = "Welcome to the winter of my discontent.\n"; int fd = open("testopen.txt", O_RDWR|O_CREAT|O_SYNC|O_DIRECT, S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR); int len; if(fd < 0) { printf("Unable to open file, errno is %d.\n", errno); } else { printf("Got fd %d.\n", fd); if((len = write(fd, message, strlen(message))) < 0) { printf("Unable to write to file, len is %d, errno is %d.\n", len, errno); } else { printf("%d bytes written to file.\n", len); } } close(fd); printf("End of program...\n"); return 0; } [unhandled content-type:application/pgp-signature] |  |