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Remove dependency on sharetab file and refactor sharing logic

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== Motivation and Context

The current implementation of 'sharenfs' and 'sharesmb' relies on
the use of the sharetab file. The use of this file is os-specific
and not required by linux or freebsd. Currently the code must
maintain updates to this file which adds complexity and presents
a significant performance impact when sharing many datasets. In
addition, concurrently running 'zfs sharenfs' command results in
missing entries in the sharetab file leading to unexpected failures.

== Description

This change removes the sharetab logic from the linux and freebsd
implementation of 'sharenfs' and 'sharesmb'. It still preserves an
os-specific library which contains the logic required for sharing
NFS or SMB. The following entry points exist in the vastly simplified
libshare library:

- sa_enable_share -- shares a dataset but may not commit the change
- sa_disable_share -- unshares a dataset but may not commit the change
- sa_is_shared -- determine if a dataset is shared
- sa_commit_share -- notify NFS/SMB subsystem to commit the shares
- sa_validate_shareopts -- determine if sharing options are valid

The sa_commit_share entry point is provided as a performance enhancement
and is not required. The sa_enable_share/sa_disable_share may commit
the share as part of the implementation. Libshare provides a framework
for both NFS and SMB but some operating systems may not fully support
these protocols or all features of the protocol.

NFS Operation:
For linux, libshare updates /etc/exports.d/zfs.exports to add
and remove shares and then commits the changes by invoking
'exportfs -r'. This file, is automatically read by the kernel NFS
implementation which makes for better integration with the NFS systemd
service. For FreeBSD, libshare updates /etc/zfs/exports to add and
remove shares and then commits the changes by sending a SIGHUP to
mountd.

SMB Operation:
For linux, libshare adds and removes files in /var/lib/samba/usershares
by calling the 'net' command directly. There is no need to commit the
changes. FreeBSD does not support SMB.

== Performance Results

To test sharing performance we created a pool with an increasing number
of datasets and invoked various zfs actions that would enable and
disable sharing. The performance testing was limited to NFS sharing.
The following tests were performed on an 8 vCPU system with 128GB and
a pool comprised of 4 50GB SSDs:

Scale testing:
- Share all filesystems in parallel -- zfs sharenfs=on <dataset> &
- Unshare all filesystems in parallel -- zfs sharenfs=off <dataset> &

Functional testing:
- share each filesystem serially -- zfs share -a
- unshare each filesystem serially -- zfs unshare -a
- reset sharenfs property and unshare -- zfs inherit -r sharenfs <pool>

For 'zfs sharenfs=on' scale testing we saw an average reduction in time
of 89.43% and for 'zfs sharenfs=off' we saw an average reduction in time
of 83.36%.

Functional testing also shows a huge improvement:
- zfs share -- 97.97% reduction in time
- zfs unshare -- 96.47% reduction in time
- zfs inhert -r sharenfs -- 99.01% reduction in time

Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed-by: Bryant G. Ly <bryangly@gmail.com>
Signed-off-by: George Wilson <gwilson@delphix.com>
External-Issue: DLPX-68690
Closes #1603
Closes #7692
Closes #7943
Closes #10300
This commit is contained in:
George Wilson
2020-07-13 11:19:18 -05:00
committed by GitHub
parent e59a377a8f
commit c15d36c674
30 changed files with 1587 additions and 1693 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/libzfs/os/linux/libzfs_mount_os.c
+1 -234
View File
@@ -22,7 +22,7 @@
/*
* Copyright 2015 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2014, 2019 by Delphix. All rights reserved.
* Copyright (c) 2014, 2020 by Delphix. All rights reserved.
* Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>
* Copyright 2017 RackTop Systems.
* Copyright (c) 2018 Datto Inc.
@@ -50,239 +50,6 @@
#include "libzfs_impl.h"
#include <thread_pool.h>
/*
* zfs_init_libshare(zhandle, service)
*
* Initialize the libshare API if it hasn't already been initialized.
* In all cases it returns 0 if it succeeded and an error if not. The
* service value is which part(s) of the API to initialize and is a
* direct map to the libshare sa_init(service) interface.
*/
int
zfs_init_libshare(libzfs_handle_t *zhandle, int service)
{
int ret = SA_OK;
if (ret == SA_OK && zhandle->libzfs_shareflags & ZFSSHARE_MISS) {
/*
* We had a cache miss. Most likely it is a new ZFS
* dataset that was just created. We want to make sure
* so check timestamps to see if a different process
* has updated any of the configuration. If there was
* some non-ZFS change, we need to re-initialize the
* internal cache.
*/
zhandle->libzfs_shareflags &= ~ZFSSHARE_MISS;
if (sa_needs_refresh(zhandle->libzfs_sharehdl)) {
zfs_uninit_libshare(zhandle);
zhandle->libzfs_sharehdl = sa_init(service);
}
}
if (ret == SA_OK && zhandle && zhandle->libzfs_sharehdl == NULL)
zhandle->libzfs_sharehdl = sa_init(service);
if (ret == SA_OK && zhandle->libzfs_sharehdl == NULL)
ret = SA_NO_MEMORY;
return (ret);
}
/*
* Share the given filesystem according to the options in the specified
* protocol specific properties (sharenfs, sharesmb). We rely
* on "libshare" to do the dirty work for us.
*/
int
zfs_share_proto(zfs_handle_t *zhp, zfs_share_proto_t *proto)
{
char mountpoint[ZFS_MAXPROPLEN];
char shareopts[ZFS_MAXPROPLEN];
char sourcestr[ZFS_MAXPROPLEN];
libzfs_handle_t *hdl = zhp->zfs_hdl;
sa_share_t share;
zfs_share_proto_t *curr_proto;
zprop_source_t sourcetype;
int err, ret;
if (!zfs_is_mountable(zhp, mountpoint, sizeof (mountpoint), NULL, 0))
return (0);
for (curr_proto = proto; *curr_proto != PROTO_END; curr_proto++) {
/*
* Return success if there are no share options.
*/
if (zfs_prop_get(zhp, proto_table[*curr_proto].p_prop,
shareopts, sizeof (shareopts), &sourcetype, sourcestr,
ZFS_MAXPROPLEN, B_FALSE) != 0 ||
strcmp(shareopts, "off") == 0)
continue;
ret = zfs_init_libshare(hdl, SA_INIT_SHARE_API);
if (ret != SA_OK) {
(void) zfs_error_fmt(hdl, EZFS_SHARENFSFAILED,
dgettext(TEXT_DOMAIN, "cannot share '%s': %s"),
zfs_get_name(zhp), sa_errorstr(ret));
return (-1);
}
/*
* If the 'zoned' property is set, then zfs_is_mountable()
* will have already bailed out if we are in the global zone.
* But local zones cannot be NFS servers, so we ignore it for
* local zones as well.
*/
if (zfs_prop_get_int(zhp, ZFS_PROP_ZONED))
continue;
share = sa_find_share(hdl->libzfs_sharehdl, mountpoint);
if (share == NULL) {
/*
* This may be a new file system that was just
* created so isn't in the internal cache
* (second time through). Rather than
* reloading the entire configuration, we can
* assume ZFS has done the checking and it is
* safe to add this to the internal
* configuration.
*/
if (sa_zfs_process_share(hdl->libzfs_sharehdl,
NULL, NULL, mountpoint,
proto_table[*curr_proto].p_name, sourcetype,
shareopts, sourcestr, zhp->zfs_name) != SA_OK) {
(void) zfs_error_fmt(hdl,
proto_table[*curr_proto].p_share_err,
dgettext(TEXT_DOMAIN, "cannot share '%s'"),
zfs_get_name(zhp));
return (-1);
}
hdl->libzfs_shareflags |= ZFSSHARE_MISS;
share = sa_find_share(hdl->libzfs_sharehdl,
mountpoint);
}
if (share != NULL) {
err = sa_enable_share(share,
proto_table[*curr_proto].p_name);
if (err != SA_OK) {
(void) zfs_error_fmt(hdl,
proto_table[*curr_proto].p_share_err,
dgettext(TEXT_DOMAIN, "cannot share '%s'"),
zfs_get_name(zhp));
return (-1);
}
} else {
(void) zfs_error_fmt(hdl,
proto_table[*curr_proto].p_share_err,
dgettext(TEXT_DOMAIN, "cannot share '%s'"),
zfs_get_name(zhp));
return (-1);
}
}
return (0);
}
/*
* Unshare a filesystem by mountpoint.
*/
int
unshare_one(libzfs_handle_t *hdl, const char *name, const char *mountpoint,
zfs_share_proto_t proto)
{
sa_share_t share;
int err;
char *mntpt;
/*
* Mountpoint could get trashed if libshare calls getmntany
* which it does during API initialization, so strdup the
* value.
*/
mntpt = zfs_strdup(hdl, mountpoint);
/* make sure libshare initialized */
if ((err = zfs_init_libshare(hdl, SA_INIT_SHARE_API)) != SA_OK) {
free(mntpt); /* don't need the copy anymore */
return (zfs_error_fmt(hdl, proto_table[proto].p_unshare_err,
dgettext(TEXT_DOMAIN, "cannot unshare '%s': %s"),
name, sa_errorstr(err)));
}
share = sa_find_share(hdl->libzfs_sharehdl, mntpt);
free(mntpt); /* don't need the copy anymore */
if (share != NULL) {
err = sa_disable_share(share, proto_table[proto].p_name);
if (err != SA_OK) {
return (zfs_error_fmt(hdl,
proto_table[proto].p_unshare_err,
dgettext(TEXT_DOMAIN, "cannot unshare '%s': %s"),
name, sa_errorstr(err)));
}
} else {
return (zfs_error_fmt(hdl, proto_table[proto].p_unshare_err,
dgettext(TEXT_DOMAIN, "cannot unshare '%s': not found"),
name));
}
return (0);
}
/*
* Search the sharetab for the given mountpoint and protocol, returning
* a zfs_share_type_t value.
*/
zfs_share_type_t
is_shared_impl(libzfs_handle_t *hdl, const char *mountpoint,
zfs_share_proto_t proto)
{
char buf[MAXPATHLEN], *tab;
char *ptr;
if (hdl->libzfs_sharetab == NULL)
return (SHARED_NOT_SHARED);
/* Reopen ZFS_SHARETAB to prevent reading stale data from open file */
if (freopen(ZFS_SHARETAB, "r", hdl->libzfs_sharetab) == NULL)
return (SHARED_NOT_SHARED);
(void) fseek(hdl->libzfs_sharetab, 0, SEEK_SET);
while (fgets(buf, sizeof (buf), hdl->libzfs_sharetab) != NULL) {
/* the mountpoint is the first entry on each line */
if ((tab = strchr(buf, '\t')) == NULL)
continue;
*tab = '\0';
if (strcmp(buf, mountpoint) == 0) {
/*
* the protocol field is the third field
* skip over second field
*/
ptr = ++tab;
if ((tab = strchr(ptr, '\t')) == NULL)
continue;
ptr = ++tab;
if ((tab = strchr(ptr, '\t')) == NULL)
continue;
*tab = '\0';
if (strcmp(ptr,
proto_table[proto].p_name) == 0) {
switch (proto) {
case PROTO_NFS:
return (SHARED_NFS);
case PROTO_SMB:
return (SHARED_SMB);
default:
return (0);
}
}
}
}
return (SHARED_NOT_SHARED);
}
#define ZS_COMMENT 0x00000000 /* comment */
#define ZS_ZFSUTIL 0x00000001 /* caller is zfs(8) */