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OpenZFS 9880 - Race in ZFS parallel mount

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Porting Notes:
* Not required for Linux since the zone is always global.  But
  we'll want this change if we start using the zones code.

Authored by: Andy Fiddaman <omnios@citrus-it.co.uk>
Reviewed by: Jason King <jason.king@joyent.com>
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: Tom Caputi <tcaputi@datto.com>
Approved by: Joshua M. Clulow <josh@sysmgr.org>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://www.illumos.org/issues/9880
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/bc4c0ff134
Closes #8189
This commit is contained in:
Andy Fiddaman 2018-10-20 14:48:39 -07:00 committed by Brian Behlendorf
parent 4b611761bd
commit e63ac16d25
1 changed files with 31 additions and 3 deletions
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34
lib/libzfs/libzfs_mount.c
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@ -26,6 +26,7 @@
* Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com> * Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>
* Copyright 2017 RackTop Systems. * Copyright 2017 RackTop Systems.
* Copyright (c) 2018 Datto Inc. * Copyright (c) 2018 Datto Inc.
* Copyright 2018 OmniOS Community Edition (OmniOSce) Association.
*/ */
/* /*
@ -1217,19 +1218,28 @@ zfs_iter_cb(zfs_handle_t *zhp, void *data)
/* /*
* Sort comparator that compares two mountpoint paths. We sort these paths so * Sort comparator that compares two mountpoint paths. We sort these paths so
* that subdirectories immediately follow their parents. This means that we * that subdirectories immediately follow their parents. This means that we
* effectively treat the '/' character as the lowest value non-nul char. An * effectively treat the '/' character as the lowest value non-nul char.
* example sorted list using this comparator would look like: * Since filesystems from non-global zones can have the same mountpoint
* as other filesystems, the comparator sorts global zone filesystems to
* the top of the list. This means that the global zone will traverse the
* filesystem list in the correct order and can stop when it sees the
* first zoned filesystem. In a non-global zone, only the delegated
* filesystems are seen.
*
* An example sorted list using this comparator would look like:
* *
* /foo * /foo
* /foo/bar * /foo/bar
* /foo/bar/baz * /foo/bar/baz
* /foo/baz * /foo/baz
* /foo.bar * /foo.bar
* /foo (NGZ1)
* /foo (NGZ2)
* *
* The mounting code depends on this ordering to deterministically iterate * The mounting code depends on this ordering to deterministically iterate
* over filesystems in order to spawn parallel mount tasks. * over filesystems in order to spawn parallel mount tasks.
*/ */
int static int
mountpoint_cmp(const void *arga, const void *argb) mountpoint_cmp(const void *arga, const void *argb)
{ {
zfs_handle_t *const *zap = arga; zfs_handle_t *const *zap = arga;
@ -1241,6 +1251,14 @@ mountpoint_cmp(const void *arga, const void *argb)
const char *a = mounta; const char *a = mounta;
const char *b = mountb; const char *b = mountb;
boolean_t gota, gotb; boolean_t gota, gotb;
uint64_t zoneda, zonedb;
zoneda = zfs_prop_get_int(za, ZFS_PROP_ZONED);
zonedb = zfs_prop_get_int(zb, ZFS_PROP_ZONED);
if (zoneda && !zonedb)
return (1);
if (!zoneda && zonedb)
return (-1);
gota = (zfs_get_type(za) == ZFS_TYPE_FILESYSTEM); gota = (zfs_get_type(za) == ZFS_TYPE_FILESYSTEM);
if (gota) { if (gota) {
@ -1461,6 +1479,8 @@ void
zfs_foreach_mountpoint(libzfs_handle_t *hdl, zfs_handle_t **handles, zfs_foreach_mountpoint(libzfs_handle_t *hdl, zfs_handle_t **handles,
size_t num_handles, zfs_iter_f func, void *data, boolean_t parallel) size_t num_handles, zfs_iter_f func, void *data, boolean_t parallel)
{ {
zoneid_t zoneid = getzoneid();
/* /*
* The ZFS_SERIAL_MOUNT environment variable is an undocumented * The ZFS_SERIAL_MOUNT environment variable is an undocumented
* variable that can be used as a convenience to do a/b comparison * variable that can be used as a convenience to do a/b comparison
@ -1495,6 +1515,14 @@ zfs_foreach_mountpoint(libzfs_handle_t *hdl, zfs_handle_t **handles,
*/ */
for (int i = 0; i < num_handles; for (int i = 0; i < num_handles;
i = non_descendant_idx(handles, num_handles, i)) { i = non_descendant_idx(handles, num_handles, i)) {
/*
* Since the mountpoints have been sorted so that the zoned
* filesystems are at the end, a zoned filesystem seen from
* the global zone means that we're done.
*/
if (zoneid == GLOBAL_ZONEID &&
zfs_prop_get_int(handles[i], ZFS_PROP_ZONED))
break;
zfs_dispatch_mount(hdl, handles, num_handles, i, func, data, zfs_dispatch_mount(hdl, handles, num_handles, i, func, data,
tp); tp);
} }