From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:43216 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754234AbaFLGWl (ORCPT ); Thu, 12 Jun 2014 02:22:41 -0400 From: Anand Jain To: linux-btrfs@vger.kernel.org Cc: wangsl.fnst@cn.fujitsu.com, Anand Jain Subject: [PATCH 1/1] btrfs: looping 'mkfs.btrfs -f ' may fail with EBUSY Date: Thu, 12 Jun 2014 14:25:00 +0800 Message-Id: <1402554300-13931-1-git-send-email-Anand.Jain@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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 .. \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 --- 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