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Hi, I have an application which is the following :- int main() { int no_bytes,retval,file_desc,bytes; unsigned long i; char buffer[BUFFER_SIZE]; unsigned long buff; memset(buffer,0,BUFFER_SIZE); for (i = 0; i < BUFFER_SIZE; i++) { buffer[i]='a'; } int fd = open("/dev/sga",O_RDWR); if (fd < 0) { printf("open failed\n"); exit(1); } bytes = write(fd,buffer,BUFFER_SIZE); lseek(fd,SEEK_SET,0); memset(buffer,0,BUFFER_SIZE); bytes = read(fd,buffer,BUFFER_SIZE); write(1,buffer,BUFFER_SIZE); return 0; } My driver code which is the request function looks like this :- #define SECTOR_SIZE 512 static int nsectors = 2000; static void block_dev_request(request_queue_t *rq) { struct request *req; printk(KERN_ALERT "Inside
block_dev_request\n"); while ((req=elv_next_request(rq)) != NULL) { struct block_dev *blk_dev =
req->rq_disk->private_data; if (!blk_fs_request(req)) { printk(KERN_ALERT "Skip non-fs
request\n"); end_request(req,0); continue; } else { block_transfer(blk_dev,req->sector,req->current_nr_sectors,req->buffer,rq_data_dir(req)); end_request(req,1); } } } static void block_transfer(struct block_dev *dev, unsigned
long sector, unsigned long nsect, char* buffer, int write) { unsigned long offset = sector*SECTOR_SIZE; // since
it is a multiple of 512 bytes unsigned long nbytes = nsect*SECTOR_SIZE;// no. of
sectors transferred in multiples of 512 bytes // This is meant for checking whether the beginning sector
bytes + no. of sectors transferred in terms of bytes exceed the total no. of
bytes i.e. 2000*512 i.e. 1MB if ((offset+nbytes) > dev->size) { printk(KERN_ALERT "Beyond end write
(%ld %ld)\n", offset,nbytes); return; } if (write) { memcpy(dev->data+offset,buffer,nbytes); printk(KERN_ALERT "Inside write
operation buffer = %s\n",buffer); } else { memcpy(buffer,dev->data+offset, nbytes); printk(KERN_ALERT "Inside read
operation buffer = %s\n",buffer); } } However after executing insmod’ding this and executing
the application , I get read operation first and then the write, when my write
comes first and then the read. What could be the reason? TIA. This is how the logs looks. Sep 26 11:53:00 san172 kernel: In REQUEST_MODE_SIMPLE Sep 26 11:53:00 san172 kernel: device->gd->major = 252 Sep 26 11:57:09 san172 kernel: iNSIDE block_dev_open Sep 26 11:57:09 san172 kernel: USERS in open = 1 Sep 26 11:57:09 san172 kernel: Inside block_dev_request Sep 26 11:57:09 san172 kernel: Inside read operation buffer
= Sep 26 11:57:09 san172 kernel: Inside block_dev_request Sep 26 11:57:09 san172 kernel: Inside read operation buffer
= Sep 26 11:57:09 san172 kernel: Inside read operation buffer
= ° Sep 26 11:57:09 san172 kernel: Inside read operation buffer
= Sep 26 11:57:09 san172 kernel: Inside read operation buffer
= , Sep 26 11:57:09 san172 kernel: Inside block_dev_request Sep 26 11:57:09 san172 kernel: Inside write operation buffer
= aaaaaaaaaa¨Ý Sep 26 11:57:09 san172 kernel: Releasing the block device Sep 26 11:57:09 san172 kernel: USERS in release = 0 http://www.patni.com World-Wide Partnerships. World-Class Solutions. _____________________________________________________________________ This e-mail message may contain proprietary, confidential or legally privileged information for the sole use of the person or entity to whom this message was originally addressed. Any review, e-transmission dissemination or other use of or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you have received this e-mail in error kindly delete this e-mail from your records. If it appears that this mail has been forwarded to you without proper authority, please notify us immediately at netadmin@xxxxxxxxx and delete this mail. _____________________________________________________________________ |
