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open_dev_excl: allow device to be read-only. 

For many operations we don't need a writable device.  So if
opening O_RDWR fails in open_dev_excl, then try again O_RDONLY.

If we really needed write, a subsequent operation will failed.  But
if we didn't, we succeed when otherwise we wouldn't have.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2011-03-24 14:21:58 +11:00
parent 972728bb1b
commit 7187750e8d
1 changed files with 6 additions and 1 deletions
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7
util.c
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@ -1015,12 +1015,17 @@ int open_dev_excl(int devnum)
{
char buf[20];
int i;
int flags = O_RDWR;
sprintf(buf, "%d:%d", dev2major(devnum), dev2minor(devnum));
for (i=0 ; i<25 ; i++) {
int fd = dev_open(buf, O_RDWR|O_EXCL);
int fd = dev_open(buf, flags|O_EXCL);
if (fd >= 0)
return fd;
if (errno == EACCES && flags == O_RDWR) {
flags = O_RDONLY;
continue;
}
if (errno != EBUSY)
return fd;
usleep(200000);