On Tue, 12 Apr 2005 18:16:40 +0200 Yves Crespin wrote:
| I've got compilation error when I call vmalloc() from a user program
| (w/o defined __KENEL).
Where did vmalloc() come from?
I said malloc(), not vmalloc().
| How can I obtains an buffer alignement from a "user program" ?
I actually left that as an exercise (after I did it at home
last night). Did you read the hint (below)?
| >so in your program, malloc() the buf [pointer] (larger than needed)
| >and then align it to a page boundary and pass that aligned pointer
| >to read().
'man malloc' refers to posix_memalign(). That's not what I
used to test it, but if it works, it should be a good choice.
| Randy.Dunlap wrote:
|
| >On Mon, 11 Apr 2005 21:14:17 +0200 Yves Crespin wrote:
| >
| >| Hello,
| >|
| >| Using O_DIRECT flag, read() failed and errno is EINVAL.
| >| kernel 2.4.22
| >| Filesystem Ext3 mount on /home
| >| What's wrong ?
| >| Thanks
| >
| >In fs/buffer.c, it wants the buffer & the length (size) to be aligned:
| >
| >function: brw_kiovec()
| >
| > /*
| > * First, do some alignment and validity checks
| > */
| > for (i = 0; i < nr; i++) {
| > iobuf = iovec[i];
| > if ((iobuf->offset & (size-1)) ||
| > (iobuf->length & (size-1)))
| > return -EINVAL;
| > if (!iobuf->nr_pages)
| > panic("brw_kiovec: iobuf not initialised");
| > }
| >
| >so in your program, malloc() the buf [pointer] (larger than needed)
| >and then align it to a page boundary and pass that aligned pointer
| >to read().
| >
| >
| >| /* --- start code --- */
| >| #include <stdio.h>
| >| #include <unistd.h>
| >| #include <stdlib.h>
| >| #include <sys/types.h>
| >| #include <sys/stat.h>
| >| #include <fcntl.h>
| >| #include <errno.h>
| >|
| >| #define O_BINARY 0
| >|
| >| int main(int argc,char *argv[])
| >| {
| >| struct stat sbuf;
| >| char buf[8192];
| >| int openFlags;
| >| int fd;
| >| int nb;
| >| int size;
| >|
| >| if (argc!=2){
| >| printf("Missing file name\n");
| >| exit(2);
| >| }
| >| openFlags = O_RDWR|O_BINARY|O_NOCTTY;
| >| openFlags |= O_DIRECT; /* Not POSIX */
| >| fd = open(argv[1],openFlags,0666);
| >| if (fd==-1){
| >| printf("open failed [%s] %#o %#o errno
| >| %d\n",argv[1],openFlags,0666,errno);
| >| exit(1);
| >| }
| >| if (fstat(fd,&sbuf)<0){
| >| printf("fstat failed\n");
| >| exit(1);
| >| }
| >| size = sbuf.st_blksize;
| >| if (size > sizeof(buf)){
| >| printf("Page size too big\n");
| >| exit(3);
| >| }
| >| if (size > sbuf.st_size){
| >| printf("File too small\n");
| >| exit(3);
| >| }
| >| nb = read(fd,buf,size);
| >| if (nb != size){
| >| printf("read failed fd %d size %d nb %d errno
| >| %d\n",fd,size,nb,errno);
| >| exit(1);
| >| }
| >| if (close(fd)){
| >| printf("close failed\n");
| >| exit(1);
| >| }
| >| return 0;
| >| }
---
~Randy
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