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8115 parallel zfs mount
@@ -20,11 +20,11 @@
*/
/*
* Copyright 2015 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2014, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2014, 2017 by Delphix. All rights reserved.
* Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>
* Copyright 2017 Joyent, Inc.
* Copyright 2017 RackTop Systems.
*/
@@ -77,19 +77,23 @@
#include <zone.h>
#include <sys/mntent.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
+#include <sys/taskq.h>
#include <libzfs.h>
#include "libzfs_impl.h"
#include <libshare.h>
#include <sys/systeminfo.h>
#define MAXISALEN 257 /* based on sysinfo(2) man page */
+static int mount_tq_nthr = 512; /* taskq threads for multi-threaded mounting */
+
+static void zfs_mount_task(void *);
static int zfs_share_proto(zfs_handle_t *, zfs_share_proto_t *);
zfs_share_type_t zfs_is_shared_proto(zfs_handle_t *, char **,
zfs_share_proto_t);
/*
@@ -1075,29 +1079,36 @@
*/
(void) rmdir(mountpoint);
}
}
+/*
+ * Add the given zfs handle to the cb_handles array, dynamically reallocating
+ * the array if it is out of space.
+ */
void
libzfs_add_handle(get_all_cb_t *cbp, zfs_handle_t *zhp)
{
if (cbp->cb_alloc == cbp->cb_used) {
size_t newsz;
- void *ptr;
+ zfs_handle_t **newhandles;
- newsz = cbp->cb_alloc ? cbp->cb_alloc * 2 : 64;
- ptr = zfs_realloc(zhp->zfs_hdl,
- cbp->cb_handles, cbp->cb_alloc * sizeof (void *),
- newsz * sizeof (void *));
- cbp->cb_handles = ptr;
+ newsz = cbp->cb_alloc != 0 ? cbp->cb_alloc * 2 : 64;
+ newhandles = zfs_realloc(zhp->zfs_hdl,
+ cbp->cb_handles, cbp->cb_alloc * sizeof (zfs_handle_t *),
+ newsz * sizeof (zfs_handle_t *));
+ cbp->cb_handles = newhandles;
cbp->cb_alloc = newsz;
}
cbp->cb_handles[cbp->cb_used++] = zhp;
}
+/*
+ * Recursive helper function used during file system enumeration
+ */
static int
-mount_cb(zfs_handle_t *zhp, void *data)
+zfs_iter_cb(zfs_handle_t *zhp, void *data)
{
get_all_cb_t *cbp = data;
if (!(zfs_get_type(zhp) & ZFS_TYPE_FILESYSTEM)) {
zfs_close(zhp);
@@ -1119,108 +1130,353 @@
zfs_close(zhp);
return (0);
}
libzfs_add_handle(cbp, zhp);
- if (zfs_iter_filesystems(zhp, mount_cb, cbp) != 0) {
+ if (zfs_iter_filesystems(zhp, zfs_iter_cb, cbp) != 0) {
zfs_close(zhp);
return (-1);
}
return (0);
}
+/*
+ * Sort comparator that compares two mountpoint paths. We sort these paths so
+ * that subdirectories immediately follow their parents. This means that we
+ * effectively treat the '/' character as the lowest value non-nul char. An
+ * example sorted list using this comparator would look like:
+ *
+ * /foo
+ * /foo/bar
+ * /foo/bar/baz
+ * /foo/baz
+ * /foo.bar
+ *
+ * The mounting code depends on this ordering to deterministically iterate
+ * over filesystems in order to spawn parallel mount tasks.
+ */
int
-libzfs_dataset_cmp(const void *a, const void *b)
+mountpoint_cmp(const void *arga, const void *argb)
{
- zfs_handle_t **za = (zfs_handle_t **)a;
- zfs_handle_t **zb = (zfs_handle_t **)b;
+ zfs_handle_t *const *zap = arga;
+ zfs_handle_t *za = *zap;
+ zfs_handle_t *const *zbp = argb;
+ zfs_handle_t *zb = *zbp;
char mounta[MAXPATHLEN];
char mountb[MAXPATHLEN];
+ const char *a = mounta;
+ const char *b = mountb;
boolean_t gota, gotb;
- if ((gota = (zfs_get_type(*za) == ZFS_TYPE_FILESYSTEM)) != 0)
- verify(zfs_prop_get(*za, ZFS_PROP_MOUNTPOINT, mounta,
+ gota = (zfs_get_type(za) == ZFS_TYPE_FILESYSTEM);
+ if (gota) {
+ verify(zfs_prop_get(za, ZFS_PROP_MOUNTPOINT, mounta,
sizeof (mounta), NULL, NULL, 0, B_FALSE) == 0);
- if ((gotb = (zfs_get_type(*zb) == ZFS_TYPE_FILESYSTEM)) != 0)
- verify(zfs_prop_get(*zb, ZFS_PROP_MOUNTPOINT, mountb,
+ }
+ gotb = (zfs_get_type(zb) == ZFS_TYPE_FILESYSTEM);
+ if (gotb) {
+ verify(zfs_prop_get(zb, ZFS_PROP_MOUNTPOINT, mountb,
sizeof (mountb), NULL, NULL, 0, B_FALSE) == 0);
+ }
- if (gota && gotb)
- return (strcmp(mounta, mountb));
+ if (gota && gotb) {
+ while (*a != '\0' && (*a == *b)) {
+ a++;
+ b++;
+ }
+ if (*a == *b)
+ return (0);
+ if (*a == '\0')
+ return (-1);
+ if (*b == '\0')
+ return (1);
+ if (*a == '/')
+ return (-1);
+ if (*b == '/')
+ return (1);
+ return (*a < *b ? -1 : *a > *b);
+ }
if (gota)
return (-1);
if (gotb)
return (1);
- return (strcmp(zfs_get_name(a), zfs_get_name(b)));
+ /*
+ * If neither filesystem has a mountpoint, revert to sorting by
+ * dataset name.
+ */
+ return (strcmp(zfs_get_name(za), zfs_get_name(zb)));
}
/*
+ * Return true if path2 is a child of path1.
+ */
+static boolean_t
+libzfs_path_contains(const char *path1, const char *path2)
+{
+ return (strstr(path2, path1) == path2 && path2[strlen(path1)] == '/');
+}
+
+/*
+ * Given a mountpoint specified by idx in the handles array, find the first
+ * non-descendent of that mountpoint and return its index. Descendant paths
+ * start with the parent's path. This function relies on the ordering
+ * enforced by mountpoint_cmp().
+ */
+static int
+non_descendant_idx(zfs_handle_t **handles, size_t num_handles, int idx)
+{
+ char parent[ZFS_MAXPROPLEN];
+ char child[ZFS_MAXPROPLEN];
+ int i;
+
+ verify(zfs_prop_get(handles[idx], ZFS_PROP_MOUNTPOINT, parent,
+ sizeof (parent), NULL, NULL, 0, B_FALSE) == 0);
+
+ for (i = idx + 1; i < num_handles; i++) {
+ verify(zfs_prop_get(handles[i], ZFS_PROP_MOUNTPOINT, child,
+ sizeof (child), NULL, NULL, 0, B_FALSE) == 0);
+ if (!libzfs_path_contains(parent, child))
+ break;
+ }
+ return (i);
+}
+
+typedef struct mnt_param {
+ libzfs_handle_t *mnt_hdl;
+ taskq_t *mnt_tq;
+ zfs_handle_t **mnt_zhps; /* filesystems to mount */
+ size_t mnt_num_handles;
+ int mnt_idx; /* Index of selected entry to mount */
+ zfs_iter_f mnt_func;
+ void *mnt_data;
+} mnt_param_t;
+
+/*
+ * Allocate and populate the parameter struct for mount function, and
+ * schedule mounting of the entry selected by idx.
+ */
+static void
+zfs_dispatch_mount(libzfs_handle_t *hdl, zfs_handle_t **handles,
+ size_t num_handles, int idx, zfs_iter_f func, void *data, taskq_t *tq)
+{
+ mnt_param_t *mnt_param = zfs_alloc(hdl, sizeof (mnt_param_t));
+
+ mnt_param->mnt_hdl = hdl;
+ mnt_param->mnt_tq = tq;
+ mnt_param->mnt_zhps = handles;
+ mnt_param->mnt_num_handles = num_handles;
+ mnt_param->mnt_idx = idx;
+ mnt_param->mnt_func = func;
+ mnt_param->mnt_data = data;
+
+ (void) taskq_dispatch(tq, zfs_mount_task, (void*)mnt_param, TQ_SLEEP);
+}
+
+/*
+ * This is the structure used to keep state of mounting or sharing operations
+ * during a call to zpool_enable_datasets().
+ */
+typedef struct mount_state {
+ /*
+ * ms_mntstatus is set to -1 if any mount fails. While multiple threads
+ * could update this variable concurrently, no synchronization is
+ * needed as it's only ever set to -1.
+ */
+ int ms_mntstatus;
+ int ms_mntflags;
+ const char *ms_mntopts;
+} mount_state_t;
+
+static int
+zfs_mount_one(zfs_handle_t *zhp, void *arg)
+{
+ mount_state_t *ms = arg;
+ int ret = 0;
+
+ if (zfs_mount(zhp, ms->ms_mntopts, ms->ms_mntflags) != 0)
+ ret = ms->ms_mntstatus = -1;
+ return (ret);
+}
+
+static int
+zfs_share_one(zfs_handle_t *zhp, void *arg)
+{
+ mount_state_t *ms = arg;
+ int ret = 0;
+
+ if (zfs_share(zhp) != 0)
+ ret = ms->ms_mntstatus = -1;
+ return (ret);
+}
+
+/*
+ * Task queue function to mount one file system. On completion, it finds and
+ * schedules its children to be mounted. This depends on the sorting done in
+ * zfs_foreach_mountpoint(). Note that the degenerate case (chain of entries
+ * each descending from the previous) will have no parallelism since we always
+ * have to wait for the parent to finish mounting before we can schedule
+ * its children.
+ */
+static void
+zfs_mount_task(void *arg)
+{
+ mnt_param_t *mp = arg;
+ int idx = mp->mnt_idx;
+ zfs_handle_t **handles = mp->mnt_zhps;
+ size_t num_handles = mp->mnt_num_handles;
+ char mountpoint[ZFS_MAXPROPLEN];
+
+ verify(zfs_prop_get(handles[idx], ZFS_PROP_MOUNTPOINT, mountpoint,
+ sizeof (mountpoint), NULL, NULL, 0, B_FALSE) == 0);
+
+ if (mp->mnt_func(handles[idx], mp->mnt_data) != 0)
+ return;
+
+ /*
+ * We dispatch tasks to mount filesystems with mountpoints underneath
+ * this one. We do this by dispatching the next filesystem with a
+ * descendant mountpoint of the one we just mounted, then skip all of
+ * its descendants, dispatch the next descendant mountpoint, and so on.
+ * The non_descendant_idx() function skips over filesystems that are
+ * descendants of the filesystem we just dispatched.
+ */
+ for (int i = idx + 1; i < num_handles;
+ i = non_descendant_idx(handles, num_handles, i)) {
+ char child[ZFS_MAXPROPLEN];
+ verify(zfs_prop_get(handles[i], ZFS_PROP_MOUNTPOINT,
+ child, sizeof (child), NULL, NULL, 0, B_FALSE) == 0);
+
+ if (!libzfs_path_contains(mountpoint, child))
+ break; /* not a descendant, return */
+ zfs_dispatch_mount(mp->mnt_hdl, handles, num_handles, i,
+ mp->mnt_func, mp->mnt_data, mp->mnt_tq);
+ }
+ free(mp);
+}
+
+/*
+ * Issue the func callback for each ZFS handle contained in the handles
+ * array. This function is used to mount all datasets, and so this function
+ * guarantees that filesystems for parent mountpoints are called before their
+ * children. As such, before issuing any callbacks, we first sort the array
+ * of handles by mountpoint.
+ *
+ * Callbacks are issued in one of two ways:
+ *
+ * 1. Sequentially: If the parallel argument is B_FALSE or the ZFS_SERIAL_MOUNT
+ * environment variable is set, then we issue callbacks sequentially.
+ *
+ * 2. In parallel: If the parallel argument is B_TRUE and the ZFS_SERIAL_MOUNT
+ * environment variable is not set, then we use a taskq to dispatch threads
+ * to mount filesystems is parallel. This function dispatches tasks to mount
+ * the filesystems at the top-level mountpoints, and these tasks in turn
+ * are responsible for recursively mounting filesystems in their children
+ * mountpoints.
+ */
+void
+zfs_foreach_mountpoint(libzfs_handle_t *hdl, zfs_handle_t **handles,
+ size_t num_handles, zfs_iter_f func, void *data, boolean_t parallel)
+{
+ /*
+ * The ZFS_SERIAL_MOUNT environment variable is an undocumented
+ * variable that can be used as a convenience to do a/b comparison
+ * of serial vs. parallel mounting.
+ */
+ boolean_t serial_mount = !parallel ||
+ (getenv("ZFS_SERIAL_MOUNT") != NULL);
+
+ /*
+ * Sort the datasets by mountpoint. See mountpoint_cmp for details
+ * of how these are sorted.
+ */
+ qsort(handles, num_handles, sizeof (zfs_handle_t *), mountpoint_cmp);
+
+ if (serial_mount) {
+ for (int i = 0; i < num_handles; i++) {
+ func(handles[i], data);
+ }
+ return;
+ }
+
+ /*
+ * Issue the callback function for each dataset using a parallel
+ * algorithm that uses a taskq to manage threads.
+ */
+ taskq_t *tq = taskq_create("mount_taskq", mount_tq_nthr, 0,
+ mount_tq_nthr, mount_tq_nthr, TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
+
+ /*
+ * There may be multiple "top level" mountpoints outside of the pool's
+ * root mountpoint, e.g.: /foo /bar. Dispatch a mount task for each of
+ * these.
+ */
+ for (int i = 0; i < num_handles;
+ i = non_descendant_idx(handles, num_handles, i)) {
+ zfs_dispatch_mount(hdl, handles, num_handles, i, func, data,
+ tq);
+ }
+
+ taskq_wait(tq); /* wait for all scheduled mounts to complete */
+ taskq_destroy(tq);
+}
+
+/*
* Mount and share all datasets within the given pool. This assumes that no
- * datasets within the pool are currently mounted. Because users can create
- * complicated nested hierarchies of mountpoints, we first gather all the
- * datasets and mountpoints within the pool, and sort them by mountpoint. Once
- * we have the list of all filesystems, we iterate over them in order and mount
- * and/or share each one.
+ * datasets within the pool are currently mounted.
*/
#pragma weak zpool_mount_datasets = zpool_enable_datasets
int
zpool_enable_datasets(zpool_handle_t *zhp, const char *mntopts, int flags)
{
get_all_cb_t cb = { 0 };
- libzfs_handle_t *hdl = zhp->zpool_hdl;
+ mount_state_t ms = { 0 };
zfs_handle_t *zfsp;
- int i, ret = -1;
- int *good;
+ sa_init_selective_arg_t sharearg;
+ int ret = 0;
- /*
- * Gather all non-snap datasets within the pool.
- */
- if ((zfsp = zfs_open(hdl, zhp->zpool_name, ZFS_TYPE_DATASET)) == NULL)
+ if ((zfsp = zfs_open(zhp->zpool_hdl, zhp->zpool_name,
+ ZFS_TYPE_DATASET)) == NULL)
goto out;
- libzfs_add_handle(&cb, zfsp);
- if (zfs_iter_filesystems(zfsp, mount_cb, &cb) != 0)
- goto out;
- /*
- * Sort the datasets by mountpoint.
- */
- qsort(cb.cb_handles, cb.cb_used, sizeof (void *),
- libzfs_dataset_cmp);
/*
- * And mount all the datasets, keeping track of which ones
- * succeeded or failed.
+ * Gather all non-snapshot datasets within the pool. Start by adding
+ * the root filesystem for this pool to the list, and then iterate
+ * over all child filesystems.
*/
- if ((good = zfs_alloc(zhp->zpool_hdl,
- cb.cb_used * sizeof (int))) == NULL)
+ libzfs_add_handle(&cb, zfsp);
+ if (zfs_iter_filesystems(zfsp, zfs_iter_cb, &cb) != 0)
goto out;
- ret = 0;
- for (i = 0; i < cb.cb_used; i++) {
- if (zfs_mount(cb.cb_handles[i], mntopts, flags) != 0)
- ret = -1;
- else
- good[i] = 1;
- }
+ ms.ms_mntopts = mntopts;
+ ms.ms_mntflags = flags;
+ zfs_foreach_mountpoint(zhp->zpool_hdl, cb.cb_handles, cb.cb_used,
+ zfs_mount_one, &ms, B_TRUE);
+ if (ms.ms_mntstatus != 0)
+ ret = ms.ms_mntstatus;
/*
- * Then share all the ones that need to be shared. This needs
- * to be a separate pass in order to avoid excessive reloading
- * of the configuration. Good should never be NULL since
- * zfs_alloc is supposed to exit if memory isn't available.
+ * Share all filesystems that need to be shared. This needs to be
+ * a separate pass because libshare is not mt-safe, and so we need
+ * to share serially.
*/
- for (i = 0; i < cb.cb_used; i++) {
- if (good[i] && zfs_share(cb.cb_handles[i]) != 0)
- ret = -1;
- }
+ sharearg.zhandle_arr = cb.cb_handles;
+ sharearg.zhandle_len = cb.cb_used;
+ if ((ret = zfs_init_libshare_arg(zhp->zpool_hdl,
+ SA_INIT_SHARE_API_SELECTIVE, &sharearg)) != 0)
+ goto out;
- free(good);
+ ms.ms_mntstatus = 0;
+ zfs_foreach_mountpoint(zhp->zpool_hdl, cb.cb_handles, cb.cb_used,
+ zfs_share_one, &ms, B_FALSE);
+ if (ms.ms_mntstatus != 0)
+ ret = ms.ms_mntstatus;
out:
- for (i = 0; i < cb.cb_used; i++)
+ for (int i = 0; i < cb.cb_used; i++)
zfs_close(cb.cb_handles[i]);
free(cb.cb_handles);
return (ret);
}