The thread holding the O_EXCL flag seems to be BTRFS_IOC_SCAN_DEV ioctl,
which in turn calls btrfs_scan_one_device() to open dev with the O_EXCL flag.
But btrfs_scan_one_device() does not write anything to the disk.
and it is called by
. An intermediary step (not the final open_ctree) in the
mount thread to read the SB and
. btrfs-control ioctls viz BTRFS_IOC_SCAN_DEV and
BTRFS_IOC_DEVICES_READY
they don't need the O_EXCL.
test script: (run this in a loop)
static int test_skip_this_disk(char *path)
{
int fd;
char c;
printf("%s ", path);
fd = open(path, O_RDWR|O_EXCL);
if (fd < 0) {
printf("Open failed\n");
return 1;
}
/*fflush(stdout);
printf("Open Fine press enter\n");
scanf("%c", &c);*/
close(fd);
return 0;
}
main(int arg, char **argv)
{
int i;
if (arg == 1) {
printf("usage: %s <dev-with-btrfs-sb> .. \n", argv[0]);
exit(1);
}
for (i = 1; i < arg; i++)
test_skip_this_disk(argv[i]);
}
dump stack after the userland close(fd)
dump_stack+0x9/0x60
btrfs_scan_one_device+0x18d/0x1f0 [btrfs]
btrfs_control_ioctl+0xb9/0x210 [btrfs]
do_vfs_ioctl+0x84/0x4c0
inode_has_perm+0x28/0x30
file_has_perm+0x8a/0xa0
SyS_ioctl+0x91/0xa0
system_call_fastpath+0x16/0x1b
Signed-off-by: Anand Jain <Anand.Jain@xxxxxxxxxx>
---
fs/btrfs/volumes.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 636faa0..c186b5e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -914,7 +914,6 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
* later supers, using BTRFS_SUPER_MIRROR_MAX instead
*/
bytenr = btrfs_sb_offset(0);
- flags |= FMODE_EXCL;
mutex_lock(&uuid_mutex);
bdev = blkdev_get_by_path(path, flags, holder);
--
1.8.5.3
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