| Message ID | 1402554300-13931-1-git-send-email-Anand.Jain@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 06/12/2014 02:25 PM, Anand Jain wrote: > 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@oracle.com> > --- > 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; I could not think whether it will cause some big problem if we remove this flag. So Cc Chris and others. Any ideas about this problem? Thanks, Wang > mutex_lock(&uuid_mutex); > > bdev = blkdev_get_by_path(path, flags, holder); -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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);
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@oracle.com> --- fs/btrfs/volumes.c | 1 - 1 file changed, 1 deletion(-)