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Bug #5273
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Incremental zfs send unmounts underlying snapshots, causing application which opens files from the snapshots to return I/O error.
Status:
New
Priority:
High
Assignee:
-
Category:
zfs - Zettabyte File System
Start date:
2014-10-29
Due date:
% Done:
0%
Estimated time:
Difficulty:
Medium
Tags:
needs-triage
Gerrit CR:
Description
This issue is probably introduced by the fix for issue 3740 (https://www.illumos.org/issues/3740).
Here is how to reproduce:
1. Suppose there's a zpool named zp01. In terminal windows A, run the following commands:
zfs create -o mountpoint=/zp01/src zp01/src
echo abcdefghijklmnopqrstuvwxyz > /zp01/src/file
zfs snapshot zp01/src@snap01
zfs snapshot zp01/src@snap02
zfs snapshot zp01/src@snap03
zfs snapshot zp01/src@snap04
ls -l /zp01/src/.zfs/snapshot/* > /dev/null
zfs create zp01/dst
2. In terminal window B, run the following dtrace command:
dtrace -n 'fbt:zfs:zfsvfs_teardown:entry /strstr(stringof(((struct zfsvfs *)arg0)->z_vfs->vfs_mntpt->rs_string), "snapshot") != 0/ { printf("pid %d, execname %s, unmounting %d, %s, %Y", pid, execname != 0 ? execname : "NULL", arg1, stringof(((struct zfsvfs *)arg0)->z_vfs->vfs_mntpt->rs_string), walltimestamp ); stack(); ustack(); }'
3. In terminal window C, compile the attached C file, and then run it to open and read /zp01/src/.zfs/snapshot/snap02/file
-> cat read-file.c
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
char *filename = NULL;
int fd;
int ret;
char buf[16];
int seconds = 300;
if(argc >= 2) {
filename = argv[1];
if(argc >= 3) seconds = atoi(argv[2]);
}
else {
printf("%s <file name>\\n", argv[0]);
exit(1);
}
fd = open(filename, O_RDONLY);
if(fd == -1) {
perror("open");
exit(1);
}
while(seconds--) {
ret = pread(fd, buf, 16, 0);
if(ret == -1) {
perror("pread");
break;
}
sleep(1);
}
ret = close(fd);
if(ret == -1) {
perror("close");
exit(1);
}
return(0);
}
-> gcc -o read-file read-file.c
-> ./read-file /zp01/src/.zfs/snapshot/snap02/file
4. Go to terminal window A, run the following commands:
-> zfs send zp01/src@snap01 | zfs recv -e zp01/dst
-> zfs send -I zp01/src@snap01 zp01/src@snap04 | zfs recv -e -F zp01/dst
You will see the following error message in terminal window C:
pread: I/O error
close: I/O error
and in terminal window B, you will see something like the following:
CPU ID FUNCTION:NAME
5 49994 zfsvfs_teardown:entry pid 6058, execname zfs, unmounting 1, /zp01/src/.zfs/snapshot/snap01, 2014 Oct 28 23:51:14
zfs`zfs_umount+0xfc
genunix`fsop_unmount+0x1b
genunix`dounmount+0x57
zfs`zfs_unmount_snap+0x63
zfs`dsl_dataset_user_release_impl+0xc3
zfs`dsl_dataset_user_release_tmp+0x1d
zfs`dsl_dataset_user_release_onexit+0x8b
zfs`zfs_onexit_destroy+0x43
zfs`zfs_ctldev_destroy+0x18
zfs`zfsdev_close+0x89
genunix`dev_close+0x31
specfs`device_close+0xd8
specfs`spec_close+0x17b
genunix`fop_close+0x61
genunix`closef+0x5e
genunix`closeandsetf+0x398
genunix`close+0x13
unix`_sys_sysenter_post_swapgs+0x149
libc.so.1`__close+0x15
libzfs.so.1`zfs_send+0x96a
zfs`zfs_do_send+0x598
zfs`main+0x22c
zfs`_start+0x83
5 49994 zfsvfs_teardown:entry pid 6058, execname zfs, unmounting 1, /zp01/src/.zfs/snapshot/snap02, 2014 Oct 28 23:51:14
zfs`zfs_umount+0xfc
genunix`fsop_unmount+0x1b
genunix`dounmount+0x57
zfs`zfs_unmount_snap+0x63
zfs`dsl_dataset_user_release_impl+0xc3
zfs`dsl_dataset_user_release_tmp+0x1d
zfs`dsl_dataset_user_release_onexit+0x8b
zfs`zfs_onexit_destroy+0x43
zfs`zfs_ctldev_destroy+0x18
zfs`zfsdev_close+0x89
genunix`dev_close+0x31
specfs`device_close+0xd8
specfs`spec_close+0x17b
genunix`fop_close+0x61
genunix`closef+0x5e
genunix`closeandsetf+0x398
genunix`close+0x13
unix`_sys_sysenter_post_swapgs+0x149
libc.so.1`__close+0x15
libzfs.so.1`zfs_send+0x96a
zfs`zfs_do_send+0x598
zfs`main+0x22c
zfs`_start+0x83
5 49994 zfsvfs_teardown:entry pid 6058, execname zfs, unmounting 1, /zp01/src/.zfs/snapshot/snap03, 2014 Oct 28 23:51:14
zfs`zfs_umount+0xfc
genunix`fsop_unmount+0x1b
genunix`dounmount+0x57
zfs`zfs_unmount_snap+0x63
zfs`dsl_dataset_user_release_impl+0xc3
zfs`dsl_dataset_user_release_tmp+0x1d
zfs`dsl_dataset_user_release_onexit+0x8b
zfs`zfs_onexit_destroy+0x43
zfs`zfs_ctldev_destroy+0x18
zfs`zfsdev_close+0x89
genunix`dev_close+0x31
specfs`device_close+0xd8
specfs`spec_close+0x17b
genunix`fop_close+0x61
genunix`closef+0x5e
genunix`closeandsetf+0x398
genunix`close+0x13
unix`_sys_sysenter_post_swapgs+0x149
libc.so.1`__close+0x15
libzfs.so.1`zfs_send+0x96a
zfs`zfs_do_send+0x598
zfs`main+0x22c
zfs`_start+0x83
5 49994 zfsvfs_teardown:entry pid 6058, execname zfs, unmounting 1, /zp01/src/.zfs/snapshot/snap04, 2014 Oct 28 23:51:14
zfs`zfs_umount+0xfc
genunix`fsop_unmount+0x1b
genunix`dounmount+0x57
zfs`zfs_unmount_snap+0x63
zfs`dsl_dataset_user_release_impl+0xc3
zfs`dsl_dataset_user_release_tmp+0x1d
zfs`dsl_dataset_user_release_onexit+0x8b
zfs`zfs_onexit_destroy+0x43
zfs`zfs_ctldev_destroy+0x18
zfs`zfsdev_close+0x89
genunix`dev_close+0x31
specfs`device_close+0xd8
specfs`spec_close+0x17b
genunix`fop_close+0x61
genunix`closef+0x5e
genunix`closeandsetf+0x398
genunix`close+0x13
unix`_sys_sysenter_post_swapgs+0x149
libc.so.1`__close+0x15
libzfs.so.1`zfs_send+0x96a
zfs`zfs_do_send+0x598
zfs`main+0x22c
zfs`_start+0x83
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