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Message-ID: <20071212091246.GA12871@dmon-lap.sw.ru>
Date: Wed, 12 Dec 2007 12:12:47 +0300
From: Dmitry Monakhov <dmonakhov@...ru>
To: Evgeniy Polyakov <johnpol@....mipt.ru>
Cc: lkml <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [4/4] DST: Algorithms used in distributed storage.
On 14:47 Mon 10 Dec , Evgeniy Polyakov wrote:
>
> Algorithms used in distributed storage.
> Mirror and linear mapping code.
Hi, i've finally take a look on your DST solution.
It seems what your current implementation will not work on nonstandard
devices for example software raid0.
other comments are follows:
>
> Signed-off-by: Evgeniy Polyakov <johnpol@....mipt.ru>
>
>
> diff --git a/drivers/block/dst/alg_linear.c b/drivers/block/dst/alg_linear.c
> new file mode 100644
> index 0000000..9dc0976
> --- /dev/null
> +++ b/drivers/block/dst/alg_linear.c
> @@ -0,0 +1,105 @@
> +/*
> + * 2007+ Copyright (c) Evgeniy Polyakov <johnpol@....mipt.ru>
> + * All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/dst.h>
> +
> +static struct dst_alg *alg_linear;
> +
> +/*
> + * This callback is invoked when node is removed from storage.
> + */
> +static void dst_linear_del_node(struct dst_node *n)
> +{
> +}
> +
> +/*
> + * This callback is invoked when node is added to storage.
> + */
> +static int dst_linear_add_node(struct dst_node *n)
> +{
> + struct dst_storage *st = n->st;
> +
> + dprintk("%s: disk_size: %llu, node_size: %llu.\n",
> + __func__, st->disk_size, n->size);
> +
> + mutex_lock(&st->tree_lock);
> + n->start = st->disk_size;
> + st->disk_size += n->size;
> + set_capacity(st->disk, st->disk_size);
> + mutex_unlock(&st->tree_lock);
> +
> + return 0;
> +}
> +
> +static int dst_linear_remap(struct dst_request *req)
> +{
> + int err;
> +
> + if (req->node->bdev) {
> + generic_make_request(req->bio);
> + return 0;
> + }
> +
> + err = kst_check_permissions(req->state, req->bio);
> + if (err)
> + return err;
> +
> + return req->state->ops->push(req);
> +}
> +
> +/*
> + * Failover callback - it is invoked each time error happens during
> + * request processing.
> + */
> +static int dst_linear_error(struct kst_state *st, int err)
> +{
> + if (err)
> + set_bit(DST_NODE_FROZEN, &st->node->flags);
> + else
> + clear_bit(DST_NODE_FROZEN, &st->node->flags);
> + return 0;
> +}
> +
> +static struct dst_alg_ops alg_linear_ops = {
> + .remap = dst_linear_remap,
> + .add_node = dst_linear_add_node,
> + .del_node = dst_linear_del_node,
> + .error = dst_linear_error,
> + .owner = THIS_MODULE,
> +};
> +
> +static int __devinit alg_linear_init(void)
> +{
> + alg_linear = dst_alloc_alg("alg_linear", &alg_linear_ops);
> + if (!alg_linear)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +static void __devexit alg_linear_exit(void)
> +{
> + dst_remove_alg(alg_linear);
> +}
> +
> +module_init(alg_linear_init);
> +module_exit(alg_linear_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Evgeniy Polyakov <johnpol@....mipt.ru>");
> +MODULE_DESCRIPTION("Linear distributed algorithm.");
> diff --git a/drivers/block/dst/alg_mirror.c b/drivers/block/dst/alg_mirror.c
> new file mode 100644
> index 0000000..3c457ff
> --- /dev/null
> +++ b/drivers/block/dst/alg_mirror.c
> @@ -0,0 +1,1128 @@
> +/*
> + * 2007+ Copyright (c) Evgeniy Polyakov <johnpol@....mipt.ru>
> + * All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/poll.h>
> +#include <linux/dst.h>
> +
> +struct dst_mirror_node_data
> +{
> + u64 age;
> +};
> +
> +struct dst_mirror_priv
> +{
> + unsigned int chunk_num;
> +
> + u64 last_start;
> +
> + spinlock_t backlog_lock;
> + struct list_head backlog_list;
> +
> + struct dst_mirror_node_data old_data, new_data;
> +
> + unsigned long *chunk;
> +};
> +
> +static struct dst_alg *alg_mirror;
> +static struct bio_set *dst_mirror_bio_set;
> +
> +static int dst_mirror_resync(struct dst_node *n, int ndp);
> +
> +static void dst_mirror_mark_sync(struct dst_node *n)
> +{
> + if (test_bit(DST_NODE_NOTSYNC, &n->flags)) {
> + struct dst_mirror_priv *priv = n->priv;
> +
> + clear_bit(DST_NODE_NOTSYNC, &n->flags);
> + dprintk("%s: node: %p, %llu:%llu synchronization "
> + "has been completed.\n",
> + __func__, n, n->start, n->size);
> + priv->old_data.age = 0;
> + }
> +}
> +
> +static void dst_mirror_mark_notsync(struct dst_node *n)
> +{
> + if (!test_bit(DST_NODE_NOTSYNC, &n->flags)) {
> + set_bit(DST_NODE_NOTSYNC, &n->flags);
> + dprintk("%s: not synced node n: %p.\n", __func__, n);
> + }
> +}
> +
> +static void dst_mirror_mark_node_notsync(struct dst_node *n)
> +{
> + struct dst_mirror_priv *p = n->priv;
> +
> + memset(p->chunk, 0xff, DIV_ROUND_UP(p->chunk_num, BITS_PER_LONG)*sizeof(long));
> + dst_mirror_mark_notsync(n);
> + dst_mirror_resync(n, 0);
> +}
> +
> +static void dst_mirror_mark_node_sync(struct dst_node *n)
> +{
> + struct dst_mirror_priv *p = n->priv;
> +
> + memset(p->chunk, 0x0, DIV_ROUND_UP(p->chunk_num, BITS_PER_LONG)*sizeof(long));
> + dst_mirror_mark_sync(n);
> +}
> +
> +static ssize_t dst_mirror_mark_dirty(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct dst_node *n = container_of(dev, struct dst_node, device);
> +
> + dst_mirror_mark_node_notsync(n);
> + return count;
> +}
> +
> +static ssize_t dst_mirror_mark_clean(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct dst_node *n = container_of(dev, struct dst_node, device);
> +
> + dst_mirror_mark_node_sync(n);
> + return count;
> +}
> +
> +static ssize_t dst_mirror_chunk_mask_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct dst_node *n = container_of(dev, struct dst_node, device);
> + struct dst_mirror_priv *priv = n->priv;
> + unsigned int i;
> + int rest = PAGE_SIZE, rest_bits = priv->chunk_num;
> +
> + for (i = 0; i < DIV_ROUND_UP(priv->chunk_num, BITS_PER_LONG); ++i) {
> + int bit, j;
> +
> + for (j = 0; j < min(BITS_PER_LONG, rest_bits); ++j) {
> + bit = (priv->chunk[i] >> j) & 1;
> + sprintf(buf, "%c", (bit)?'+':'-');
> + buf++;
> + }
> +
> + rest_bits -= j;
> + rest -= j;
> +
> + if (rest < BITS_PER_LONG || rest_bits <= 0)
> + break;
> + }
> +
> + return PAGE_SIZE - rest;
> +}
> +
> +static struct device_attribute dst_mirror_attrs[] = {
> + __ATTR(chunks, S_IRUGO, dst_mirror_chunk_mask_show, NULL),
> + __ATTR(dirty, S_IWUSR, NULL, dst_mirror_mark_dirty),
> + __ATTR(clean, S_IWUSR, NULL, dst_mirror_mark_clean),
> +};
> +
> +/*
> + * This callback is invoked when node is removed from storage.
> + */
> +static void dst_mirror_del_node(struct dst_node *n)
> +{
> + struct dst_mirror_priv *priv = n->priv;
> + struct dst_request *req, *tmp;
> +
> + list_for_each_entry_safe(req, tmp, &priv->backlog_list, request_list_entry) {
> + kst_del_req(req);
> + kst_complete_req(req, -ENODEV);
> + }
> +
> + if (priv) {
> + vfree(priv->chunk);
> + kfree(priv);
> + n->priv = NULL;
> + }
> +
> + if (n->device.parent == &n->st->device) {
> + int i;
> +
> + for (i=0; i<ARRAY_SIZE(dst_mirror_attrs); ++i)
> + device_remove_file(&n->device, &dst_mirror_attrs[i]);
> + }
> +}
> +
> +static void dst_mirror_handle_priv(struct dst_node *n)
> +{
> + if (n->priv) {
> + int err, i;
> +
> + for (i=0; i<ARRAY_SIZE(dst_mirror_attrs); ++i)
> + err = device_create_file(&n->device,
> + &dst_mirror_attrs[i]);
> + }
> +}
> +
> +static void dst_mirror_destructor(struct bio *bio)
> +{
> + dprintk("%s: bio: %p.\n", __func__, bio);
> + bio_free(bio, dst_mirror_bio_set);
> +}
> +
> +/*
> + * This function copies node's private on-disk data from first node
> + * to the new one.
> + */
> +static int dst_mirror_get_node_data(struct dst_node *n,
> + struct dst_mirror_node_data *ndata, int old)
> +{
> + struct dst_node *first;
> + struct dst_mirror_priv *p;
> +
> + mutex_lock(&n->st->tree_lock);
> + first = dst_storage_tree_search(n->st, n->start);
> + mutex_unlock(&n->st->tree_lock);
> + if (!first) {
> + dprintk("%s: there are no nodes in the storage.\n", __func__);
> + return -ENODEV;
> + }
> +
> + p = first->priv;
> + memcpy(ndata, (old)?&p->old_data:&p->new_data, sizeof(struct dst_mirror_node_data));
> +
> + dst_node_put(first);
> + return 0;
> +}
> +
> +struct dst_mirror_ndp
> +{
> + int err;
> + struct page *page;
> + struct completion complete;
> +};
> +
> +static void dst_mirror_ndb_complete(struct dst_mirror_ndp *cmp, int err)
> +{
> + cmp->err = err;
> + dprintk("%s: completing request: cmp: %p, err: %d.\n",
> + __func__, cmp, err);
> + complete(&cmp->complete);
> +}
> +
> +static void dst_mirror_ndp_bio_endio(struct dst_request *req, int err)
> +{
> + struct dst_mirror_ndp *cmp = req->bio->bi_private;
> +
> + dst_mirror_ndb_complete(cmp, err);
> +}
> +
> +static int dst_mirror_ndp_end_io(struct bio *bio, unsigned int size, int err)
> +{
> + struct dst_mirror_ndp *cmp = bio->bi_private;
> +
> + if (bio->bi_size)
> + return 0;
> +
> + dst_mirror_ndb_complete(cmp, err);
> + return 0;
> +}
> +
> +/*
> + * This function reads or writes node's private data from underlying media.
> + */
> +static int dst_mirror_process_node_data(struct dst_node *n,
> + struct dst_mirror_node_data *ndata, int op)
> +{
> + struct bio *bio;
> + int err = -ENOMEM;
> + struct dst_mirror_ndp *cmp;
> + void *addr;
> +
> + cmp = kzalloc(sizeof(struct dst_mirror_ndp), GFP_KERNEL);
> + if (!cmp)
> + goto err_out_exit;
> +
> + cmp->page = alloc_page(GFP_NOIO);
> + if (!cmp->page)
> + goto err_out_free_cmp;
> +
> + addr = kmap(cmp->page);
> +
> + init_completion(&cmp->complete);
> +
> + if (op == WRITE)
> + memcpy(addr, ndata, sizeof(struct dst_mirror_node_data));
> +
> + bio = bio_alloc_bioset(GFP_NOIO, 1, dst_mirror_bio_set);
> + if (!bio)
> + goto err_out_free_page;
> +
> + bio->bi_rw = op;
> + bio->bi_private = cmp;
> + bio->bi_sector = n->size;
> + bio->bi_bdev = n->bdev;
> + bio->bi_destructor = dst_mirror_destructor;
> + bio->bi_end_io = dst_mirror_ndp_end_io;
> +
> + err = bio_add_pc_page(n->st->queue, bio, cmp->page, 512, 0);
> + if (err <= 0)
> + goto err_out_free_bio;
> +
> + if (n->bdev) {
> + generic_make_request(bio);
> + } else {
> + struct dst_request req;
> +
> + memset(&req, 0, sizeof(struct dst_request));
> +
> + req.node = n;
> + req.state = n->state;
> + req.start = bio->bi_sector;
> + req.size = req.orig_size = bio->bi_size;
> + req.bio = bio;
> + req.idx = bio->bi_idx;
> + req.num = bio->bi_vcnt;
> + req.flags = 0;
> + req.offset = 0;
> + req.bio_endio = &dst_mirror_ndp_bio_endio;
> + req.callback = &kst_data_callback;
> +
> + err = req.state->ops->push(&req);
> + if (err)
> + req.bio_endio(&req, err);
> + }
> +
> + dprintk("%s: waiting for completion: bio: %p, cmp: %p.\n",
> + __func__, bio, cmp);
> +
> + wait_for_completion(&cmp->complete);
> +
> + err = cmp->err;
> +
> + if (!err && (op != WRITE))
> + memcpy(ndata, addr, sizeof(struct dst_mirror_node_data));
> +
> + kunmap(cmp->page);
<< MINOR_BUG:
You has forgot to unmap page on error path, so IMHO it is better to move
kunmap to "err_out_free_cmp" label.
> +
> + dprintk("%s: freeing bio: %p, err: %d.\n", __func__, bio, err);
> +
> +err_out_free_bio:
> + bio_put(bio);
> +err_out_free_page:
> + __free_page(cmp->page);
> +err_out_free_cmp:
> + kfree(cmp);
> +err_out_exit:
> + return err;
> +}
> +
> +/*
> + * This function reads node's private data from underlying media.
> + */
> +static int dst_mirror_read_node_data(struct dst_node *n,
> + struct dst_mirror_node_data *ndata)
> +{
> + return dst_mirror_process_node_data(n, ndata, READ);
> +}
> +
> +/*
> + * This function writes node's private data from underlying media.
> + */
> +static int dst_mirror_write_node_data(struct dst_node *n,
> + struct dst_mirror_node_data *ndata)
> +{
> + dprintk("%s: writing new age: %llx, node: %p %llu-%llu.\n",
> + __func__, ndata->age, n, n->start, n->size);
> + return dst_mirror_process_node_data(n, ndata, WRITE);
> +}
> +
> +static int dst_mirror_ndp_setup(struct dst_node *n, int first_node, int clean_on_sync)
> +{
> + struct dst_mirror_priv *p = n->priv;
> + int sync = 1, err;
> +
> + err = dst_mirror_read_node_data(n, &p->old_data);
> + if (err)
> + return err;
> +
> + if (first_node) {
> + p->new_data.age = *(u64 *)&n->st;
> +
> + dprintk("%s: first age: %llx -> %llx. "
> + "Old will be set to new for the first node.\n",
> + __func__, p->old_data.age, p->new_data.age);
> +
> + err = dst_mirror_write_node_data(n, &p->new_data);
> + if (err)
> + return err;
> + p->old_data.age = p->new_data.age;
> + } else {
> + err = dst_mirror_get_node_data(n, &p->new_data, 1);
> + if (err)
> + return err;
> +
> + if (p->new_data.age != p->old_data.age) {
> + sync = 0;
> + dprintk("%s: node %llu:%llu is not synced with the first "
> + "node (old != new): %llx != %llx.\n",
> + __func__, n->start, n->start+n->size,
> + p->old_data.age, p->new_data.age);
> + err = dst_mirror_get_node_data(n, &p->new_data, 0);
> + if (err)
> + return err;
> + } else {
> + err = dst_mirror_get_node_data(n, &p->new_data, 0);
> + if (err)
> + return err;
> +
> + err = dst_mirror_write_node_data(n, &p->new_data);
> + if (err)
> + return err;
> +
> + dprintk("%s: node %llu:%llu is in sync with the first node.\n",
> + __func__, n->start, n->start+n->size);
> + }
> + }
> +
> + if (!sync)
> + dst_mirror_mark_node_notsync(n);
> + else if (clean_on_sync)
> + dst_mirror_mark_node_sync(n);
> +
> + dprintk("%s: age: old: %llx, new: %llx.\n", __func__, p->old_data.age, p->new_data.age);
> +
> + return 0;
> +}
> +
> +/*
> + * This callback is invoked when node is added to storage.
> + */
> +static int dst_mirror_add_node(struct dst_node *n)
> +{
> + struct dst_storage *st = n->st;
> + struct dst_mirror_priv *priv;
> + int err = -ENOMEM, first_node = 0;
> + u64 disk_size;
> +
> + n->size--; /* A sector size actually. */
> +
> + mutex_lock(&st->tree_lock);
> + disk_size = st->disk_size;
> + if (st->disk_size) {
> + st->disk_size = min(n->size, st->disk_size);
> + } else {
> + st->disk_size = n->size;
> + first_node = 1;
> + }
> + mutex_unlock(&st->tree_lock);
> +
> + priv = kzalloc(sizeof(struct dst_mirror_priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + priv->chunk_num = st->disk_size;
> +
> + priv->chunk = vmalloc(DIV_ROUND_UP(priv->chunk_num, BITS_PER_LONG) * sizeof(long));
<< Ohhh. My. I want to add my 500G hdd. Do you really wanna
say what i have to store 128Mb in memory object for this.
> + if (!priv->chunk)
> + goto err_out_free;
> +
> + spin_lock_init(&priv->backlog_lock);
> + INIT_LIST_HEAD(&priv->backlog_list);
> +
> + dprintk("%s: %llu:%llu, chunk_num: %u, disk_size: %llu.\n\n",
> + __func__, n->start, n->size,
> + priv->chunk_num, st->disk_size);
> +
> + n->priv_callback = &dst_mirror_handle_priv;
> + n->priv = priv;
> +
> + err = dst_mirror_ndp_setup(n, first_node, 1);
> + if (err)
> + goto err_out_free_chunk;
> +
> + return 0;
> +
> +err_out_free_chunk:
> + vfree(priv->chunk);
> +err_out_free:
> + kfree(priv);
> + n->priv = NULL;
> +
> + mutex_lock(&st->tree_lock);
> + st->disk_size = disk_size;
> + mutex_unlock(&st->tree_lock);
> + return err;
> +}
> +
> +static void dst_mirror_sync_destructor(struct bio *bio)
> +{
> + struct bio_vec *bv;
> + int i;
> +
> + bio_for_each_segment(bv, bio, i)
> + __free_page(bv->bv_page);
> + bio_free(bio, dst_mirror_bio_set);
> +}
> +
> +/*
> + * Without errors it is always called under node's request lock,
> + * so it is safe to requeue them.
> + */
> +static void dst_mirror_bio_error(struct dst_request *req, int err)
> +{
> + int i;
> + struct dst_mirror_priv *priv = req->node->priv;
> + unsigned int num, idx;
> + u64 start = req->start - to_sector(req->orig_size - req->size);
> +
> + if (err)
> + dst_mirror_mark_notsync(req->node);
> +
> + priv->last_start = req->start;
> +
> + idx = start;
> + num = to_sector(req->orig_size);
> +
> + dprintk("%s: %llu:%llu start: %llu, size: %llu, "
> + "chunk_num: %u, idx: %d, num: %d, err: %d, node: %p.\n",
> + __func__, req->node->start, req->node->size,
> + start, req->orig_size, priv->chunk_num,
> + idx, num, err, req->node);
> +
> + if (unlikely(idx >= priv->chunk_num || idx + num > priv->chunk_num)) {
> + dprintk("%s: %llu:%llu req: %p, start: %llu, orig_size: %llu, "
> + "req_start: %llu, req_size: %llu, "
> + "chunk_num: %u, idx: %d, num: %d, err: %d.\n",
> + __func__, req->node->start, req->node->size, req,
> + start, req->orig_size,
> + req->start, req->size,
> + priv->chunk_num, idx, num, err);
> + return;
> + }
> +
> + if (err) {
> + for (i=0; i<num; ++i)
> + __set_bit(idx+i, priv->chunk);
> + } else {
> + for (i=0; i<num; ++i)
> + __clear_bit(idx+i, priv->chunk);
> + }
> +}
> +
> +static void dst_mirror_sync_req_endio(struct dst_request *req, int err)
> +{
> + struct dst_node *n = req->node;
> + struct dst_mirror_priv *p = req->node->priv;
> + int i;
> + unsigned long notsync = 0;
> +
> + dst_mirror_bio_error(req, err);
> +
> + dprintk("%s: freeing bio: %p, bi_size: %u, "
> + "orig_size: %llu, req: %p, node: %p.\n",
> + __func__, req->bio, req->bio->bi_size, req->orig_size, req,
> + req->node);
> +
> + bio_put(req->bio);
> +
> + if (!test_bit(DST_NODE_NOTSYNC, &n->flags))
> + return;
> +
> + for (i = 0; i < DIV_ROUND_UP(p->chunk_num, BITS_PER_LONG); ++i) {
> + notsync = p->chunk[i];
> + if (notsync)
> + break;
> + }
> +
> + if (notsync) {
> + dprintk("%s: %d/%d sync: %lx, ffs: %lu, chunk_num (modulo %u): %d.\n",
> + __func__, i, DIV_ROUND_UP(p->chunk_num, BITS_PER_LONG),
> + notsync, __ffs(notsync), BITS_PER_LONG,
> + p->chunk_num%BITS_PER_LONG);
> + if (i != DIV_ROUND_UP(p->chunk_num, BITS_PER_LONG) - 1)
> + return;
> +
> + if (__ffs(notsync) != (p->chunk_num%BITS_PER_LONG))
> + return;
> + }
> +
> + dst_mirror_mark_sync(n);
> +}
> +
> +static int dst_mirror_sync_endio(struct bio *bio, unsigned int size, int err)
> +{
> + struct dst_request *req = bio->bi_private;
> + struct dst_node *n = req->node;
> + struct dst_mirror_priv *priv = n->priv;
> + unsigned long flags;
> +
> + dprintk("%s: bio: %p, err: %d, size: %u, req: %p.\n",
> + __func__, bio, err, bio->bi_size, req);
> +
> + if (bio->bi_size)
> + return 1;
> +
> + bio->bi_rw = WRITE;
> + bio->bi_size = req->orig_size;
> + bio->bi_sector = req->start;
> +
> + if (!err) {
> + spin_lock_irqsave(&priv->backlog_lock, flags);
> + list_add_tail(&req->request_list_entry, &priv->backlog_list);
> + spin_unlock_irqrestore(&priv->backlog_lock, flags);
> + kst_wake(req->state);
> + } else {
> + req->bio_endio(req, err);
> + dst_free_request(req);
> + }
> + return 0;
> +}
> +
> +static int dst_mirror_sync_block(struct dst_node *n,
> + int bit_start, int bit_num)
> +{
> + u64 start = to_bytes(bit_start);
> + u32 size = to_bytes(bit_num);
> + struct bio *bio;
> + unsigned int nr_pages = DIV_ROUND_UP(size, PAGE_SIZE), i;
> + struct page *page;
> + int err = -ENOMEM;
> + struct dst_request *req;
> +
> + dprintk("%s: bit_start: %d, bit_num: %d, start: %llu, nr_pages: %u, "
> + "disk_size: %llu.\n",
> + __func__, bit_start, bit_num, start, nr_pages,
> + n->st->disk_size);
> +
> + while (nr_pages) {
> + req = dst_clone_request(NULL, n->w->req_pool);
> + if (!req)
> + return -ENOMEM;
> +
> + bio = bio_alloc_bioset(GFP_NOIO, nr_pages, dst_mirror_bio_set);
> + if (!bio)
> + goto err_out_free_req;
> +
> + bio->bi_rw = READ;
> + bio->bi_private = req;
> + bio->bi_sector = to_sector(start);
> + bio->bi_bdev = NULL;
> + bio->bi_destructor = dst_mirror_sync_destructor;
> + bio->bi_end_io = dst_mirror_sync_endio;
> +
> + for (i = 0; i < nr_pages; ++i) {
> + err = -ENOMEM;
> +
> + page = alloc_page(GFP_NOIO);
> + if (!page)
> + break;
> +
> + err = bio_add_pc_page(n->st->queue, bio, page,
> + min_t(u32, PAGE_SIZE, size), 0);
> + if (err <= 0)
> + break;
> + size -= err;
> + err = 0;
> + }
> +
> + if (err && !bio->bi_vcnt)
> + goto err_out_put_bio;
> +
> + req->node = n;
> + req->state = n->state;
> + req->start = bio->bi_sector;
> + req->size = req->orig_size = bio->bi_size;
> + req->bio = bio;
> + req->idx = bio->bi_idx;
> + req->num = bio->bi_vcnt;
> + req->flags = DST_REQ_CHECK_QUEUE;
> + req->offset = 0;
> + req->bio_endio = &dst_mirror_sync_req_endio;
> + req->callback = &kst_data_callback;
> +
> + dprintk("%s: start: %llu, size: %llu/%u, bio: %p, req: %p, "
> + "node: %p.\n",
> + __func__, req->start, req->size, nr_pages, bio,
> + req, req->node);
> +
> + err = n->st->queue->make_request_fn(n->st->queue, bio);
<< Why direct make_request_fn instead of generic_make_request?
> + if (err)
> + goto err_out_put_bio;
> +
> + nr_pages -= bio->bi_vcnt;
> + start += bio->bi_size;
> + }
> +
> + return 0;
> +
> +err_out_put_bio:
> + bio_put(bio);
> +err_out_free_req:
> + dst_free_request(req);
> + return err;
> +}
> +
> +/*
> + * Resync logic.
> + *
> + * System allocates and queues requests for number of regions.
> + * Each request initially is reading from the one of the nodes.
> + * When it is completed, system checks if given region was already
> + * written to, and in such case just drops read request, otherwise
> + * it writes it to the node being updated. Any write clears not-uptodate
> + * bit, which is used as a flag that region must be synchronized or not.
> + * Reading is never performed from the node under resync.
> + */
> +static int dst_mirror_resync(struct dst_node *n, int ndp)
> +{
> + struct dst_mirror_priv *priv = n->priv;
> + int err = 0, sync = 1, total = priv->chunk_num;
> + unsigned int i;
> +
> + dprintk("%s: node: %p, %llu:%llu synchronization has been started.\n",
> + __func__, n, n->start, n->size);
> +
> + if (ndp) {
> + err = dst_mirror_ndp_setup(n, 0, 0);
> + if (err)
> + return err;
> + }
> +
> + for (i = 0; i < DIV_ROUND_UP(priv->chunk_num, BITS_PER_LONG); ++i) {
> + int bit, num, start;
> + unsigned long word = priv->chunk[i];
> +
> + if (!word)
> + continue;
> +
> + num = 0;
> + start = -1;
> + while (word && num < BITS_PER_LONG) {
> + bit = __ffs(word);
> + if (start == -1)
> + start = bit;
> + num++;
<< MINOR_BUG: Seems you have misstyped here. AFAIU @num represent position
of last non zero bit (start + num == last_non_zero_bit_pos)
if (start == -1) {
start = bit;
num = 1;
} else
num += bit;
> + word >>= (bit+1);
> +
> + if (--total == 0)
> + break;
> + }
> +
> + if (start != -1) {
> + err = dst_mirror_sync_block(n, start + i*BITS_PER_LONG,
> + num);
> + if (err)
> + break;
> + sync = 0;
> + }
> +
> + if (total == 0)
> + break;
> + }
> +
> + return err;
> +}
> +
> +static int dst_mirror_end_io(struct bio *bio, unsigned int size, int err)
> +{
> + struct dst_request *req = bio->bi_private;
> +
> + if (bio->bi_size)
> + return 0;
> +
> + dprintk("%s: req: %p, bio: %p, req->bio: %p, err: %d.\n",
> + __func__, req, bio, req->bio, err);
> + req->bio_endio(req, err);
> + bio_put(bio);
> + return 0;
> +}
> +
> +static void dst_mirror_read_endio(struct dst_request *req, int err)
> +{
> + dst_mirror_bio_error(req, err);
> +
> + if (err && req->state)
> + kst_wake(req->state);
> +
> + if (!err || req->callback)
> + kst_bio_endio(req, err);
> +}
> +
> +static void dst_mirror_write_endio(struct dst_request *req, int err)
> +{
> + dst_mirror_bio_error(req, err);
> +
> + if (err && req->state)
> + kst_wake(req->state);
> +
> + req = req->priv;
> +
> + dprintk("%s: req: %p, priv: %p err: %d, bio: %p, "
> + "cnt: %d, orig_size: %llu.\n",
> + __func__, req, req->priv, err, req->bio,
> + atomic_read(&req->refcnt), req->orig_size);
> +
> + if (atomic_dec_and_test(&req->refcnt)) {
> + bio_endio(req->bio, req->orig_size, 0);
> + dst_free_request(req);
> + }
> +}
> +
> +static int dst_mirror_process_request_nosync(struct dst_request *req,
> + struct dst_node *n)
> +{
> + int err = 0;
> +
> + /*
> + * Block layer requires to clone a bio.
> + */
> + if (n->bdev) {
> + struct bio *clone = bio_alloc_bioset(GFP_NOIO,
> + req->bio->bi_max_vecs, dst_mirror_bio_set);
> +
> + __bio_clone(clone, req->bio);
> +
> + clone->bi_bdev = n->bdev;
> + clone->bi_destructor = dst_mirror_destructor;
> + clone->bi_private = req;
> + clone->bi_end_io = &dst_mirror_end_io;
> +
> + dprintk("%s: clone: %p, bio: %p, req: %p.\n",
> + __func__, clone, req->bio, req);
> +
> + generic_make_request(clone);
> + } else {
> + struct dst_request nr;
> + /*
> + * Network state processing engine will clone request
> + * by itself if needed. We can not use the same structure
> + * here, since number of its fields will be modified.
> + */
> + memcpy(&nr, req, sizeof(struct dst_request));
> +
> + nr.node = n;
> + nr.state = n->state;
> + nr.priv = req;
> +
> + err = kst_check_permissions(n->state, req->bio);
> + if (!err)
> + err = n->state->ops->push(&nr);
> + }
> +
> + dprintk("%s: req: %p, n: %p, bdev: %p, err: %d.\n",
> + __func__, req, n, n->bdev, err);
> +
> + return err;
> +}
> +
> +static void dst_mirror_sync_requeue(struct dst_node *n)
> +{
> + struct dst_mirror_priv *p = n->priv;
> + struct dst_request *req;
> + unsigned int num, idx, i;
> + u64 start;
> + unsigned long flags;
> + int err;
> +
> + while (!list_empty(&p->backlog_list)) {
> + req = NULL;
> + spin_lock_irqsave(&p->backlog_lock, flags);
> + if (!list_empty(&p->backlog_list)) {
> + req = list_entry(p->backlog_list.next,
> + struct dst_request,
> + request_list_entry);
> + list_del_init(&req->request_list_entry);
> + }
> + spin_unlock_irqrestore(&p->backlog_lock, flags);
> +
> + if (!req)
> + break;
> +
> + start = req->start - to_sector(req->orig_size - req->size);
> +
> + idx = start;
> + num = to_sector(req->orig_size);
> +
> + for (i=0; i<num; ++i)
> + if (test_bit(idx+i, p->chunk))
> + break;
> +
> + dprintk("%s: idx: %u, num: %u, i: %u, req: %p, "
> + "start: %llu, size: %llu.\n",
> + __func__, idx, num, i, req,
> + req->start, req->orig_size);
> +
> + err = -1;
> + if (i != num) {
> + err = dst_mirror_process_request_nosync(req, n);
> + if (!err)
> + dst_free_request(req);
> + }
> +
> + if (err)
> + kst_complete_req(req, err);
> + }
> +
> + if (!test_bit(DST_NODE_NOTSYNC, &n->flags) &&
> + p->old_data.age != p->new_data.age) {
> + dst_mirror_write_node_data(n, &p->new_data);
> + p->old_data.age = p->new_data.age;
> + }
> +}
> +
> +static int dst_mirror_process_request(struct dst_request *req,
> + struct dst_node *n)
> +{
> + dst_mirror_sync_requeue(n);
> + return dst_mirror_process_request_nosync(req, n);
> +}
> +
> +static int dst_mirror_write(struct dst_request *oreq)
> +{
> + struct dst_node *n, *node = oreq->node;
> + struct dst_request *req;
> + int num, err = 0, err_num = 0, orig_num;
> +
> + req = dst_clone_request(oreq, oreq->node->w->req_pool);
> + if (!req) {
> + err = -ENOMEM;
> + goto err_out_exit;
> + }
> +
> + req->priv = req;
> +
> + /*
> + * This logic is pretty simple - req->bio_endio will not
> + * call bio_endio() until all mirror devices completed
> + * processing of the request (no matter with or without error).
> + * Mirror's req->bio_endio callback will take care of that.
> + */
> + orig_num = num = atomic_read(&req->node->shared_num) + 1;
> + atomic_set(&req->refcnt, num);
> +
> + req->bio_endio = &dst_mirror_write_endio;
> +
> + dprintk("\n%s: req: %p, mirror to %d nodes.\n",
> + __func__, req, num);
> +
> + err = dst_mirror_process_request(req, node);
> + if (err)
> + err_num++;
> +
> + if (--num) {
> + list_for_each_entry(n, &node->shared, shared) {
> + dprintk("\n%s: req: %p, start: %llu, size: %llu, "
> + "num: %d, n: %p, state: %p.\n",
> + __func__, req, req->start,
> + req->size, num, n, n->state);
> +
> + err = dst_mirror_process_request(req, n);
> + if (err)
> + err_num++;
> +
> + if (--num <= 0)
> + break;
> + }
> + }
> +
> + if (err_num == orig_num) {
> + dprintk("%s: req: %p, num: %d, err: %d.\n",
> + __func__, req, num, err);
> + err = -ENODEV;
> + goto err_out_exit;
> + }
> +
> + return 0;
> +
> +err_out_exit:
> + return err;
> +}
> +
> +static int dst_mirror_read(struct dst_request *req)
> +{
> + struct dst_node *node = req->node, *n, *min_dist_node;
> + struct dst_mirror_priv *priv = node->priv;
> + u64 dist, d;
> + int err;
> +
> + req->bio_endio = &dst_mirror_read_endio;
> +
> + do {
> + err = -ENODEV;
> + min_dist_node = NULL;
> + dist = -1ULL;
> +
> + /*
> + * Reading is never performed from the node under resync.
> + * If this will cause any troubles (like all nodes must be
> + * resynced between each other), this check can be removed
> + * and per-chunk dirty bit can be tested instead.
> + */
> +
> + if (!test_bit(DST_NODE_NOTSYNC, &node->flags)) {
> + priv = node->priv;
> + if (req->start > priv->last_start)
> + dist = req->start - priv->last_start;
> + else
> + dist = priv->last_start - req->start;
> + min_dist_node = req->node;
> + }
> +
> + list_for_each_entry(n, &node->shared, shared) {
> + if (test_bit(DST_NODE_NOTSYNC, &n->flags))
> + continue;
> +
> + priv = n->priv;
> +
> + if (req->start > priv->last_start)
> + d = req->start - priv->last_start;
> + else
> + d = priv->last_start - req->start;
> +
> + if (d < dist)
> + min_dist_node = n;
> + }
> +
> + if (!min_dist_node)
> + break;
> +
> + req->node = min_dist_node;
> + req->state = req->node->state;
> +
> + if (req->node->bdev) {
> + req->bio->bi_bdev = req->node->bdev;
> + generic_make_request(req->bio);
> + err = 0;
> + break;
> + }
> +
> + err = req->state->ops->push(req);
> + if (err) {
> + dprintk("%s: req: %p, bio: %p, node: %p, err: %d.\n",
> + __func__, req, req->bio, min_dist_node, err);
> + dst_mirror_mark_notsync(req->node);
> + }
> + } while (err && min_dist_node);
> +
> + if (err || !min_dist_node) {
> + dprintk("%s: req: %p, bio: %p, node: %p, err: %d.\n",
> + __func__, req, req->bio, min_dist_node, err);
> + if (!err)
> + err = -ENODEV;
> + }
> + dprintk("%s: req: %p, err: %d.\n", __func__, req, err);
> + return err;
> +}
> +
> +/*
> + * This callback is invoked from block layer request processing function,
> + * its task is to remap block request to different nodes.
> + */
> +static int dst_mirror_remap(struct dst_request *req)
> +{
> + int (*remap[])(struct dst_request *) =
> + {&dst_mirror_read, &dst_mirror_write};
> +
> + return remap[bio_rw(req->bio) == WRITE](req);
> +}
> +
> +static int dst_mirror_error(struct kst_state *st, int err)
> +{
> + struct dst_request *req, *tmp;
> + unsigned int revents = st->socket->ops->poll(NULL, st->socket, NULL);
> +
> + dprintk("%s: err: %d, revents: %x, notsync: %d.\n",
> + __func__, err, revents,
> + test_bit(DST_NODE_NOTSYNC, &st->node->flags));
> +
> + if (err == -EEXIST)
> + return err;
> +
> + if (!(revents & (POLLERR | POLLHUP)) &&
> + (err == -EPIPE || err == -ECONNRESET)) {
> + if (test_bit(DST_NODE_NOTSYNC, &st->node->flags)) {
> + return dst_mirror_resync(st->node, 1);
> + }
> + return 0;
> + }
> +
> + if (atomic_read(&st->node->shared_num) == 0 &&
> + !st->node->shared_head) {
> + dprintk("%s: this node is the only one in the mirror, "
> + "can not mark it notsync.\n", __func__);
> + return err;
> + }
> +
> + dst_mirror_mark_notsync(st->node);
> +
> + mutex_lock(&st->request_lock);
> + list_for_each_entry_safe(req, tmp, &st->request_list,
> + request_list_entry) {
> + kst_del_req(req);
> + dprintk("%s: requeue [%c], start: %llu, idx: %d,"
> + " num: %d, size: %llu, offset: %u, err: %d.\n",
> + __func__, (bio_rw(req->bio) == WRITE)?'W':'R',
> + req->start, req->idx, req->num, req->size,
> + req->offset, err);
> +
> + if (bio_rw(req->bio) != WRITE) {
> + req->start -= to_sector(req->orig_size - req->size);
> + req->size = req->orig_size;
> + req->flags &= ~(DST_REQ_HEADER_SENT | DST_REQ_CHEKSUM_RECV);
> + req->idx = 0;
> + if (dst_mirror_read(req))
> + dst_free_request(req);
> + } else {
> + kst_complete_req(req, err);
> + }
> + }
> + mutex_unlock(&st->request_lock);
> + return err;
> +}
> +
> +static struct dst_alg_ops alg_mirror_ops = {
> + .remap = dst_mirror_remap,
> + .add_node = dst_mirror_add_node,
> + .del_node = dst_mirror_del_node,
> + .error = dst_mirror_error,
> + .owner = THIS_MODULE,
> +};
> +
> +static int __devinit alg_mirror_init(void)
> +{
> + int err = -ENOMEM;
> +
> + dst_mirror_bio_set = bioset_create(256, 256);
> + if (!dst_mirror_bio_set)
> + return -ENOMEM;
> +
> + alg_mirror = dst_alloc_alg("alg_mirror", &alg_mirror_ops);
> + if (!alg_mirror)
> + goto err_out;
> +
> + return 0;
> +
> +err_out:
> + bioset_free(dst_mirror_bio_set);
> + return err;
> +}
> +
> +static void __devexit alg_mirror_exit(void)
> +{
> + dst_remove_alg(alg_mirror);
> + bioset_free(dst_mirror_bio_set);
> +}
> +
> +module_init(alg_mirror_init);
> +module_exit(alg_mirror_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Evgeniy Polyakov <johnpol@....mipt.ru>");
> +MODULE_DESCRIPTION("Mirror distributed algorithm.");
>
> --
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