Hi Shesha,
I don't believe that you specified which kernel release/version you are
experiencing this with.
Also, I am not sure what you are trying to do, but there is an easier way
of doing it.
In Linux, I believe it is actually preferred that you open a device in raw
mode by using the O_DIRECT flag when you call open().
This code below will probably no longer work anyways once 2.7 comes out,
as this raw device interface may become deprecated. So I would probably
not bother getting it to work with the current implementation.
But, that's just my opinion.
Best Regards,
Arthur Perry
Lead Linux Developer / Linux Systems Architect
Validation, CSU Celestica
Sair/Linux Gnu Certified Professional, 2000
On Mon, 3 May 2004, Shesha Sreenivasamurthy wrote:
> Hi All,
> In the user program below, I am trying to open, read, and close raw
> devices. The block devices sda-sdi are mapped to raw1-raw9. If a disk is
> missing, then after I get a read error I close that devices, remove that
> device from the proc file system and go on reading the next device. At
> this point, while I try to read from the next device (next disk after
> the missing one), kernel calls a BUG!! in bdput() inside
> "fs/block_dev.c". If I postpone closing the missing disk (line 75) by
> storing the device handler of the missing disk in an integer array, and
> closing it after the loop (at line 87) then everying works well. I could
> not find an explanation for this phenomenon. Can any one please help me
> understand this.....
>
> -Shesha
>
> -------------------------------------------------------------------------------------------------------------
> 1 #include <string.h>
> 2 #include <sys/types.h>
> 3 #include <unistd.h>
> 4 #include <sys/stat.h>
> 5 #include <fcntl.h>
> 6 #include <linux/fs.h>
> 7 #include <signal.h>
> 8 #include <syslog.h>
> 9 #include <stdio.h>
> 10
> 11
> 12
> 13 /* Raw devices require the memory to be aligned at sector boundry */
> 14
> 15 char * allign_memory(char * buffer, int boundry)
> 16 {
> 17 unsigned long addrs, rem;
> 18 char * buf=buffer;
> 19 addrs=(unsigned long)buffer;
> 20 rem=addrs%boundry;
> 21
> 22 if(rem)
> 23 buf = ((char *) addrs+(boundry-rem));
> 24 return buf;
> 25 }
> 26
> 27
> 28 void scsi_single_dev(char *cmd, int host, int channel, int id,
> int lun)
> 29 {
> 30 FILE *fd;
> 31
> 32 fd = fopen("/proc/scsi/scsi", "w");
> 33
> 34 if (fd != NULL)
> 35 {
> 36 fprintf(fd, "scsi %s-single-device %d %d %d %d",
> 37 cmd, host, channel, id, lun);
> 38 fclose(fd);
> 39 printf("scsi-single %s for %d:%d:%d:%d",cmd, host, channel,
> id, lun);
> 40 }
> 41 else
> 42 printf("could not open /proc/scsi/scsi for
> %s-single-device", cmd);
> 43 }
> 44
> 45 int main() {
> 46
> 47 char *t_buf=NULL, *buf=NULL;
> 48 int dev=-1, rc=-1,i=1;
> 49 char devname[16];
> 50 int bad[10];
> 51 int cnt=-1;
> 52
> 53 t_buf=(char *) malloc(4096+512);
> 54
> 55 if(t_buf) {
> 56
> 57 /* Raw devices require the memory to be aligned at
> sector boundry */
> 58 buf=allign_memory(t_buf, 512);
>
> 59 while(i<10) {
> 60 printf("ITERATION : %d\n", i);
> 61 sprintf(devname,"/dev/raw/raw%d",i);
> 62 printf("RAW DEV NAME = %s\n", devname);
> 63
> 64 dev = open(devname, O_RDWR);
> 65 printf("DEV Handler =%d\n", dev);
> 66 rc = ioctl(dev, BLKFLSBUF, 0);
> 67
> 68 if(dev != -1) {
> 69 rc = lseek(dev, 0, SEEK_SET);
> 70 printf("RC lseek =%d\n", rc);
> 71 if(rc != -1)
> 72 rc=read(dev, buf, 4096);
> 73 printf("RC read =%d\n", rc);
> 74
> 75 close(dev);
> 76
> 77 if(rc==-1)
> 78 scsi_single_dev("remove", 0, 0, i, 0);
> 79
> 80 }
> 81 i++;
> 82 }
> 83 } else
> 84 printf("tbuf NULL\n");
> 85
> 86 free(t_buf);
> 87 return 0;
> 88
> 89 }
> -------------------------------------------------------------------------------------------------------------
>
>
>
> -
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