On Wed, Mar 01, 2023 at 01:41:33PM -0700, Logan Gunthorpe wrote:
> Add the --write-zeros option for Create which will send a write zeros
> request to all the disks before assembling the array. After zeroing
> the array, the disks will be in a known clean state and the initial
> sync may be skipped.
>
> Writing zeroes is best used when there is a hardware offload method
> to zero the data. But even still, zeroing can take several minutes on
> a large device. Because of this, all disks are zeroed in parallel using
> their own forked process and a message is printed to the user. The main
> process will proceed only after all the zeroing processes have completed
> successfully.
>
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Acked-by: Kinga Tanska <kinga.tanska@xxxxxxxxxxxxxxx>
> Reviewed-by: Xiao Ni <xni@xxxxxxxxxx>
> Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
Acked-by: Coly Li <colyli@xxxxxxx>
Thanks.
> ---
> Create.c | 176 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> ReadMe.c | 2 +
> mdadm.c | 9 +++
> mdadm.h | 5 ++
> 4 files changed, 190 insertions(+), 2 deletions(-)
>
> diff --git a/Create.c b/Create.c
> index 4acda30c5256..bbe9e13dc76d 100644
> --- a/Create.c
> +++ b/Create.c
> @@ -26,6 +26,10 @@
> #include "md_u.h"
> #include "md_p.h"
> #include <ctype.h>
> +#include <fcntl.h>
> +#include <signal.h>
> +#include <sys/signalfd.h>
> +#include <sys/wait.h>
>
> static int round_size_and_verify(unsigned long long *size, int chunk)
> {
> @@ -91,9 +95,149 @@ int default_layout(struct supertype *st, int level, int verbose)
> return layout;
> }
>
> +static pid_t write_zeroes_fork(int fd, struct shape *s, struct supertype *st,
> + struct mddev_dev *dv)
> +
> +{
> + const unsigned long long req_size = 1 << 30;
> + unsigned long long offset_bytes, size_bytes, sz;
> + sigset_t sigset;
> + int ret = 0;
> + pid_t pid;
> +
> + size_bytes = KIB_TO_BYTES(s->size);
> +
> + /*
> + * If size_bytes is zero, this is a zoned raid array where
> + * each disk is of a different size and uses its full
> + * disk. Thus zero the entire disk.
> + */
> + if (!size_bytes && !get_dev_size(fd, dv->devname, &size_bytes))
> + return -1;
> +
> + if (dv->data_offset != INVALID_SECTORS)
> + offset_bytes = SEC_TO_BYTES(dv->data_offset);
> + else
> + offset_bytes = SEC_TO_BYTES(st->data_offset);
> +
> + pr_info("zeroing data from %lld to %lld on: %s\n",
> + offset_bytes, size_bytes, dv->devname);
> +
> + pid = fork();
> + if (pid < 0) {
> + pr_err("Could not fork to zero disks: %s\n", strerror(errno));
> + return pid;
> + } else if (pid != 0) {
> + return pid;
> + }
> +
> + sigemptyset(&sigset);
> + sigaddset(&sigset, SIGINT);
> + sigprocmask(SIG_UNBLOCK, &sigset, NULL);
> +
> + while (size_bytes) {
> + /*
> + * Split requests to the kernel into 1GB chunks seeing the
> + * fallocate() call is not interruptible and blocking a
> + * ctrl-c for several minutes is not desirable.
> + *
> + * 1GB is chosen as a compromise: the user may still have
> + * to wait several seconds if they ctrl-c on devices that
> + * zero slowly, but will reduce the number of requests
> + * required and thus the overhead on devices that perform
> + * better.
> + */
> + sz = size_bytes;
> + if (sz >= req_size)
> + sz = req_size;
> +
> + if (fallocate(fd, FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE,
> + offset_bytes, sz)) {
> + pr_err("zeroing %s failed: %s\n", dv->devname,
> + strerror(errno));
> + ret = 1;
> + break;
> + }
> +
> + offset_bytes += sz;
> + size_bytes -= sz;
> + }
> +
> + exit(ret);
> +}
> +
> +static int wait_for_zero_forks(int *zero_pids, int count)
> +{
> + int wstatus, ret = 0, i, sfd, wait_count = 0;
> + struct signalfd_siginfo fdsi;
> + bool interrupted = false;
> + sigset_t sigset;
> + ssize_t s;
> +
> + for (i = 0; i < count; i++)
> + if (zero_pids[i])
> + wait_count++;
> + if (!wait_count)
> + return 0;
> +
> + sigemptyset(&sigset);
> + sigaddset(&sigset, SIGINT);
> + sigaddset(&sigset, SIGCHLD);
> + sigprocmask(SIG_BLOCK, &sigset, NULL);
> +
> + sfd = signalfd(-1, &sigset, 0);
> + if (sfd < 0) {
> + pr_err("Unable to create signalfd: %s\n", strerror(errno));
> + return 1;
> + }
> +
> + while (1) {
> + s = read(sfd, &fdsi, sizeof(fdsi));
> + if (s != sizeof(fdsi)) {
> + pr_err("Invalid signalfd read: %s\n", strerror(errno));
> + close(sfd);
> + return 1;
> + }
> +
> + if (fdsi.ssi_signo == SIGINT) {
> + printf("\n");
> + pr_info("Interrupting zeroing processes, please wait...\n");
> + interrupted = true;
> + } else if (fdsi.ssi_signo == SIGCHLD) {
> + if (!--wait_count)
> + break;
> + }
> + }
> +
> + close(sfd);
> +
> + for (i = 0; i < count; i++) {
> + if (!zero_pids[i])
> + continue;
> +
> + waitpid(zero_pids[i], &wstatus, 0);
> + zero_pids[i] = 0;
> + if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus))
> + ret = 1;
> + }
> +
> + if (interrupted) {
> + pr_err("zeroing interrupted!\n");
> + return 1;
> + }
> +
> + if (ret)
> + pr_err("zeroing failed!\n");
> + else
> + pr_info("zeroing finished\n");
> +
> + return ret;
> +}
> +
> static int add_disk_to_super(int mdfd, struct shape *s, struct context *c,
> struct supertype *st, struct mddev_dev *dv,
> - struct mdinfo *info, int have_container, int major_num)
> + struct mdinfo *info, int have_container, int major_num,
> + int *zero_pid)
> {
> dev_t rdev;
> int fd;
> @@ -148,6 +292,14 @@ static int add_disk_to_super(int mdfd, struct shape *s, struct context *c,
> }
> st->ss->getinfo_super(st, info, NULL);
>
> + if (fd >= 0 && s->write_zeroes) {
> + *zero_pid = write_zeroes_fork(fd, s, st, dv);
> + if (*zero_pid <= 0) {
> + ioctl(mdfd, STOP_ARRAY, NULL);
> + return 1;
> + }
> + }
> +
> if (have_container && c->verbose > 0)
> pr_err("Using %s for device %d\n",
> map_dev(info->disk.major, info->disk.minor, 0),
> @@ -224,10 +376,23 @@ static int add_disks(int mdfd, struct mdinfo *info, struct shape *s,
> {
> struct mddev_dev *moved_disk = NULL;
> int pass, raid_disk_num, dnum;
> + int zero_pids[total_slots];
> struct mddev_dev *dv;
> struct mdinfo *infos;
> + sigset_t sigset, orig_sigset;
> int ret = 0;
>
> + /*
> + * Block SIGINT so the main thread will always wait for the
> + * zeroing processes when being interrupted. Otherwise the
> + * zeroing processes will finish their work in the background
> + * keeping the disk busy.
> + */
> + sigemptyset(&sigset);
> + sigaddset(&sigset, SIGINT);
> + sigprocmask(SIG_BLOCK, &sigset, &orig_sigset);
> + memset(zero_pids, 0, sizeof(zero_pids));
> +
> infos = xmalloc(sizeof(*infos) * total_slots);
> enable_fds(total_slots);
> for (pass = 1; pass <= 2; pass++) {
> @@ -261,7 +426,7 @@ static int add_disks(int mdfd, struct mdinfo *info, struct shape *s,
>
> ret = add_disk_to_super(mdfd, s, c, st, dv,
> &infos[dnum], have_container,
> - major_num);
> + major_num, &zero_pids[dnum]);
> if (ret)
> goto out;
>
> @@ -287,6 +452,10 @@ static int add_disks(int mdfd, struct mdinfo *info, struct shape *s,
> }
>
> if (pass == 1) {
> + ret = wait_for_zero_forks(zero_pids, total_slots);
> + if (ret)
> + goto out;
> +
> ret = update_metadata(mdfd, s, st, map, info,
> chosen_name);
> if (ret)
> @@ -295,7 +464,10 @@ static int add_disks(int mdfd, struct mdinfo *info, struct shape *s,
> }
>
> out:
> + if (ret)
> + wait_for_zero_forks(zero_pids, total_slots);
> free(infos);
> + sigprocmask(SIG_SETMASK, &orig_sigset, NULL);
> return ret;
> }
>
> diff --git a/ReadMe.c b/ReadMe.c
> index bd8d50d28661..db251ed2f3d4 100644
> --- a/ReadMe.c
> +++ b/ReadMe.c
> @@ -138,6 +138,7 @@ struct option long_options[] = {
> {"size", 1, 0, 'z'},
> {"auto", 1, 0, Auto}, /* also for --assemble */
> {"assume-clean",0,0, AssumeClean },
> + {"write-zeroes",0,0, WriteZeroes },
> {"metadata", 1, 0, 'e'}, /* superblock format */
> {"bitmap", 1, 0, Bitmap},
> {"bitmap-chunk", 1, 0, BitmapChunk},
> @@ -390,6 +391,7 @@ char Help_create[] =
> " --write-journal= : Specify journal device for RAID-4/5/6 array\n"
> " --consistency-policy= : Specify the policy that determines how the array\n"
> " -k : maintains consistency in case of unexpected shutdown.\n"
> +" --write-zeroes : Write zeroes to the disks before creating. This will bypass initial sync.\n"
> "\n"
> ;
>
> diff --git a/mdadm.c b/mdadm.c
> index 57e8e6fa64b9..4685ad6b06c2 100644
> --- a/mdadm.c
> +++ b/mdadm.c
> @@ -590,6 +590,10 @@ int main(int argc, char *argv[])
> s.assume_clean = 1;
> continue;
>
> + case O(CREATE, WriteZeroes):
> + s.write_zeroes = 1;
> + continue;
> +
> case O(GROW,'n'):
> case O(CREATE,'n'):
> case O(BUILD,'n'): /* number of raid disks */
> @@ -1251,6 +1255,11 @@ int main(int argc, char *argv[])
> }
> }
>
> + if (s.write_zeroes && !s.assume_clean) {
> + pr_info("Disk zeroing requested, setting --assume-clean to skip resync\n");
> + s.assume_clean = 1;
> + }
> +
> if (!mode && devs_found) {
> mode = MISC;
> devmode = 'Q';
> diff --git a/mdadm.h b/mdadm.h
> index 8bd65fba1887..211cfcd54f92 100644
> --- a/mdadm.h
> +++ b/mdadm.h
> @@ -275,6 +275,9 @@ static inline void __put_unaligned32(__u32 val, void *p)
>
> #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
>
> +#define KIB_TO_BYTES(x) ((x) << 10)
> +#define SEC_TO_BYTES(x) ((x) << 9)
> +
> extern const char Name[];
>
> struct md_bb_entry {
> @@ -435,6 +438,7 @@ extern char Version[], Usage[], Help[], OptionHelp[],
> */
> enum special_options {
> AssumeClean = 300,
> + WriteZeroes,
> BitmapChunk,
> WriteBehind,
> ReAdd,
> @@ -640,6 +644,7 @@ struct shape {
> int bitmap_chunk;
> char *bitmap_file;
> int assume_clean;
> + bool write_zeroes;
> int write_behind;
> unsigned long long size;
> unsigned long long data_offset;
> --
> 2.30.2
>
--
Coly Li
