[5/9] pohmelfs: inode operations.

[Evgeniy Polyakov]

This is a main patch which implements inode operations
(like reading and writing) and superblock processing
(filesystem registration, initial autoconfiguration
with the server like permissions, size of the exported
dir, amount of the objects created and so on).

POHMELFS relies on system's writeback cache mechanism
shown here, as long as cache coherency protocol described
later.

Signed-off-by: Evgeniy Polyakov <zbr@xxxxxxxxxxx>

diff --git a/fs/pohmelfs/inode.c b/fs/pohmelfs/inode.c
new file mode 100644
index 0000000..f66d6c6
--- /dev/null
+++ b/fs/pohmelfs/inode.c
@@ -0,0 +1,2085 @@
+/*
+ * 2007+ Copyright (c) Evgeniy Polyakov <zbr@xxxxxxxxxxx>
+ * 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/backing-dev.h>
+#include <linux/crypto.h>
+#include <linux/fs.h>
+#include <linux/jhash.h>
+#include <linux/hash.h>
+#include <linux/ktime.h>
+#include <linux/mm.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/pagevec.h>
+#include <linux/parser.h>
+#include <linux/swap.h>
+#include <linux/slab.h>
+#include <linux/statfs.h>
+#include <linux/writeback.h>
+#include <linux/quotaops.h>
+
+#include "netfs.h"
+
+#define POHMELFS_MAGIC_NUM	0x504f482e
+
+static struct kmem_cache *pohmelfs_inode_cache;
+
+/*
+ * Removes inode from all trees, drops local name cache and removes all queued
+ * requests for object removal.
+ */
+void pohmelfs_inode_del_inode(struct pohmelfs_sb *psb, struct pohmelfs_inode *pi)
+{
+	struct pohmelfs_name *n, *tmp;
+
+	mutex_lock(&pi->offset_lock);
+	pohmelfs_free_names(pi);
+
+	list_for_each_entry_safe(n, tmp, &pi->sync_create_list, sync_create_entry) {
+		list_del_init(&n->sync_create_entry);
+		list_del_init(&n->sync_del_entry);
+		kfree(n);
+	}
+
+	list_for_each_entry_safe(n, tmp, &pi->sync_del_list, sync_del_entry) {
+		list_del_init(&n->sync_create_entry);
+		list_del_init(&n->sync_del_entry);
+		kfree(n);
+	}
+	mutex_unlock(&pi->offset_lock);
+
+	dprintk("%s: deleted stuff in ino: %llu.\n", __func__, pi->ino);
+}
+
+/*
+ * Sync inode to server.
+ * Returns zero in success and negative error value otherwise.
+ * It will gather path to root directory into structures containing
+ * creation mode, permissions and names, so that the whole path
+ * to given inode could be created using only single network command.
+ */
+int pohmelfs_write_inode_create(struct inode *inode, struct netfs_trans *trans)
+{
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	int err = -ENOMEM, size;
+	struct netfs_cmd *cmd;
+	void *data;
+	int cur_len = netfs_trans_cur_len(trans);
+
+	if (unlikely(cur_len < 0))
+		return -ETOOSMALL;
+
+	cmd = netfs_trans_current(trans);
+	cur_len -= sizeof(struct netfs_cmd);
+
+	data = (void *)(cmd + 1);
+
+	mutex_lock(&psb->path_lock);
+	err = pohmelfs_construct_path(pi, data, cur_len);
+	mutex_unlock(&psb->path_lock);
+
+	dprintk("%s: cmd: %p, data: %p, len: %u, err: %u.\n",
+			__func__, cmd, data, cur_len, err);
+
+	if (err < 0)
+		goto err_out_exit;
+
+	size = err;
+
+	if (size) {
+		cmd->start = 0;
+		cmd->cmd = NETFS_CREATE;
+		cmd->size = size;
+		cmd->id = pi->ino;
+		cmd->ext = 0;
+
+		netfs_convert_cmd(cmd);
+	}
+
+	netfs_trans_update(cmd, trans, size);
+
+	return 0;
+
+err_out_exit:
+	clear_bit(NETFS_INODE_CREATED, &pi->state);
+	printk("%s: completed ino: %llu, err: %d.\n", __func__, pi->ino, err);
+	return err;
+}
+
+static int pohmelfs_write_trans_complete(struct page **pages, unsigned int page_num,
+		void *private, int err)
+{
+	unsigned i;
+
+	dprintk("%s: pages: %lu-%lu, page_num: %u, err: %d.\n",
+			__func__, pages[0]->index, pages[page_num-1]->index,
+			page_num, err);
+
+	for (i = 0; i < page_num; i++) {
+		struct page *page = pages[i];
+
+		if (!page)
+			continue;
+
+		end_page_writeback(page);
+
+		if (err < 0) {
+			SetPageError(page);
+			set_page_dirty(page);
+		}
+
+		unlock_page(page);
+		page_cache_release(page);
+
+		/* dprintk("%s: %3u/%u: page: %p.\n", __func__, i, page_num, page); */
+	}
+	return err;
+}
+
+static int pohmelfs_inode_has_dirty_pages(struct address_space *mapping, pgoff_t index)
+{
+	int ret;
+	struct page *page;
+
+	rcu_read_lock();
+	ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
+				(void **)&page, index, 1, PAGECACHE_TAG_DIRTY);
+	rcu_read_unlock();
+	return ret;
+}
+
+static int pohmelfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
+{
+	struct inode *inode = mapping->host;
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	struct backing_dev_info *bdi = mapping->backing_dev_info;
+	int err = 0;
+	int done = 0;
+	int nr_pages;
+	int created = 0;
+	pgoff_t index;
+	pgoff_t end;		/* Inclusive */
+	int scanned = 0;
+	int range_whole = 0;
+
+	if (wbc->nonblocking && bdi_write_congested(bdi)) {
+		wbc->encountered_congestion = 1;
+		return 0;
+	}
+
+	if (wbc->range_cyclic) {
+		index = mapping->writeback_index; /* Start from prev offset */
+		end = -1;
+	} else {
+		index = wbc->range_start >> PAGE_CACHE_SHIFT;
+		end = wbc->range_end >> PAGE_CACHE_SHIFT;
+		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+			range_whole = 1;
+		scanned = 1;
+	}
+retry:
+	while (!done && (index <= end)) {
+		unsigned int i = min(end - index, (pgoff_t)psb->trans_max_pages);
+		unsigned int path_len;
+		struct netfs_trans *trans;
+
+		err = pohmelfs_inode_has_dirty_pages(mapping, index);
+		if (!err)
+			break;
+
+		mutex_lock(&psb->path_lock);
+		if (!test_bit(NETFS_INODE_CREATED, &pi->state))
+			err = pohmelfs_path_length_create(pi);
+		else
+			err = pohmelfs_path_length(pi);
+		mutex_unlock(&psb->path_lock);
+
+		if (err < 0)
+			break;
+
+		path_len = err;
+
+		trans = netfs_trans_alloc(psb, path_len, 0, i);
+		if (!trans) {
+			err = -ENOMEM;
+			break;
+		}
+		trans->complete = &pohmelfs_write_trans_complete;
+
+		trans->page_num = nr_pages = find_get_pages_tag(mapping, &index,
+				PAGECACHE_TAG_DIRTY, trans->page_num,
+				trans->pages);
+
+		dprintk("%s: t: %p, nr_pages: %u, end: %lu, index: %lu, max: %u.\n",
+				__func__, trans, nr_pages, end, index, trans->page_num);
+
+		if (!nr_pages)
+			goto err_out_reset;
+		
+		if (!test_bit(NETFS_INODE_CREATED, &pi->state)) {
+			err = pohmelfs_write_inode_create(inode, trans);
+			if (err)
+				goto err_out_reset;
+			created = 1;
+		} else {
+			void *data;
+			struct netfs_cmd *cmd = netfs_trans_current(trans);
+
+			data = (void *)(cmd + 1);
+
+			mutex_lock(&psb->path_lock);
+			err = pohmelfs_construct_path_string(pi, data, path_len);
+			mutex_unlock(&psb->path_lock);
+			if (err < 0)
+				goto err_out_reset;
+
+			cmd->id = pi->ino;
+			cmd->start = 0;
+			cmd->size = err + 1;
+			cmd->cmd = NETFS_OPEN;
+			cmd->ext = O_RDWR | O_LARGEFILE;
+			cmd->csize = 0;
+			cmd->cpad = 0;
+
+			netfs_convert_cmd(cmd);
+			netfs_trans_update(cmd, trans, err + 1);
+		}
+
+		err = 0;
+		scanned = 1;
+		for (i = 0; i < trans->page_num; i++) {
+			struct page *page = trans->pages[i];
+
+			lock_page(page);
+
+			if (unlikely(page->mapping != mapping))
+				goto out_continue;
+
+			if (!wbc->range_cyclic && page->index > end) {
+				done = 1;
+				goto out_continue;
+			}
+
+			if (wbc->sync_mode != WB_SYNC_NONE)
+				wait_on_page_writeback(page);
+
+			if (PageWriteback(page) ||
+			    !clear_page_dirty_for_io(page)) {
+				dprintk("%s: not clear for io page: %p, writeback: %d.\n",
+						__func__, page, PageWriteback(page));
+				goto out_continue;
+			}
+
+			set_page_writeback(page);
+
+			trans->attached_size += page_private(page);
+			trans->attached_pages++;
+#if 0
+			dprintk("%s: %u/%u added trans: %p, gen: %u, page: %p, [High: %d], size: %lu, idx: %lu.\n",
+					__func__, i, trans->page_num, trans, trans->gen, page,
+					!!PageHighMem(page), page_private(page), page->index);
+#endif
+			wbc->nr_to_write--;
+
+			if (wbc->nr_to_write <= 0)
+				done = 1;
+			if (wbc->nonblocking && bdi_write_congested(bdi)) {
+				wbc->encountered_congestion = 1;
+				done = 1;
+			}
+
+			continue;
+out_continue:
+			unlock_page(page);
+			trans->pages[i] = NULL;
+		}
+
+		if (trans->attached_size || created) {
+			err = netfs_trans_finish(trans, psb);
+		} else {
+			netfs_trans_reset(trans);
+			netfs_trans_put(trans);
+		}
+
+		if (err)
+			break;
+
+		continue;
+
+err_out_reset:
+		trans->result = err;
+		netfs_trans_reset(trans);
+		netfs_trans_put(trans);
+		break;
+	}
+
+	if (!scanned && !done) {
+		/*
+		 * We hit the last page and there is more work to be done: wrap
+		 * back to the start of the file
+		 */
+		scanned = 1;
+		index = 0;
+		goto retry;
+	}
+
+	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
+		mapping->writeback_index = index;
+
+	return err;
+}
+
+/*
+ * Sync all not-yet-created children in given directory to the server.
+ */
+static int pohmelfs_write_inode_create_children(struct inode *inode)
+{
+	struct pohmelfs_inode *parent = POHMELFS_I(inode);
+	struct super_block *sb = inode->i_sb;
+	struct pohmelfs_name *n;
+
+	while (!list_empty(&parent->sync_create_list)) {
+		n = NULL;
+		mutex_lock(&parent->offset_lock);
+		if (!list_empty(&parent->sync_create_list)) {
+			n = list_first_entry(&parent->sync_create_list,
+				struct pohmelfs_name, sync_create_entry);
+			list_del_init(&n->sync_create_entry);
+		}
+		mutex_unlock(&parent->offset_lock);
+
+		if (!n)
+			break;
+
+		inode = ilookup(sb, n->ino);
+
+		dprintk("%s: parent: %llu, ino: %llu, inode: %p.\n",
+				__func__, parent->ino, n->ino, inode);
+
+		if (inode && (inode->i_state & I_DIRTY)) {
+			pohmelfs_meta_command(POHMELFS_I(inode),
+				NETFS_INODE_INFO, 0, NULL, NULL, 0);
+			iput(inode);
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Removes given child from given inode on server.
+ */
+static int pohmelfs_remove_child(struct pohmelfs_inode *parent, struct pohmelfs_name *n)
+{
+	dprintk("%s: parent: %llu, ino: %llu, name: '%s'.\n",
+			__func__, parent->ino, n->ino, n->data);
+
+	return pohmelfs_meta_command_data(parent, parent->ino, NETFS_REMOVE, n->data, 0, NULL, NULL, 0);
+}
+
+/*
+ * Removes all childs, marked for deletion, on server.
+ */
+static int pohmelfs_write_inode_remove_children(struct inode *inode)
+{
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	int err, error = 0;
+	struct pohmelfs_name *n, *tmp;
+
+	if (!list_empty(&pi->sync_del_list)) {
+		mutex_lock(&pi->offset_lock);
+		list_for_each_entry_safe(n, tmp, &pi->sync_del_list, sync_del_entry) {
+			list_del_init(&n->sync_del_entry);
+			list_del_init(&n->sync_create_entry);
+
+			err = pohmelfs_remove_child(pi, n);
+			if (err)
+				error = err;
+
+			kfree(n);
+		}
+		mutex_unlock(&pi->offset_lock);
+	}
+
+	return error;
+}
+
+/*
+ * Inode writeback creation completion callback.
+ * Only invoked for just created inodes, which do not have pages attached,
+ * like dirs and empty files.
+ */
+static int pohmelfs_write_inode_complete(struct page **pages, unsigned int page_num,
+		void *private, int err)
+{
+	struct inode *inode = private;
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+
+	if (inode) {
+		if (err) {
+			mark_inode_dirty(inode);
+			clear_bit(NETFS_INODE_CREATED, &pi->state);
+		} else
+			set_bit(NETFS_INODE_CREATED, &pi->state);
+
+		pohmelfs_put_inode(pi);
+	}
+
+	return err;
+}
+
+/*
+ * Writeback for given inode.
+ */
+static int pohmelfs_write_inode(struct inode *inode, int sync)
+{
+	int err;
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	struct netfs_trans *t;
+
+	if (!test_bit(NETFS_INODE_CREATED, &pi->state)) {
+		dprintk("%s: started ino: %llu.\n", __func__, pi->ino);
+
+		mutex_lock(&psb->path_lock);
+		err = pohmelfs_path_length_create(pi);
+		mutex_unlock(&psb->path_lock);
+		if (err < 0)
+			goto err_out_remove;
+
+		t = netfs_trans_alloc(psb, err + 1, 0, 0);
+		if (!t) {
+			err = -ENOMEM;
+			goto err_out_put;
+		}
+		t->complete = pohmelfs_write_inode_complete;
+		t->private = igrab(inode);
+		if (!t->private) {
+			err = -ENOENT;
+			goto err_out_put;
+		}
+
+		err = pohmelfs_write_inode_create(inode, t);
+		if (err)
+			goto err_out_put;
+
+		err = netfs_trans_finish(t, POHMELFS_SB(inode->i_sb));
+		if (err)
+			goto err_out_remove;
+	}
+
+	pohmelfs_write_inode_create_children(inode);
+	pohmelfs_write_inode_remove_children(inode);
+
+	return 0;
+
+err_out_put:
+	t->result = err;
+	netfs_trans_put(t);
+err_out_remove:
+	pohmelfs_write_inode_create_children(inode);
+	pohmelfs_write_inode_remove_children(inode);
+
+	return err;
+}
+
+/*
+ * It is not exported, sorry...
+ */
+static inline wait_queue_head_t *page_waitqueue(struct page *page)
+{
+	const struct zone *zone = page_zone(page);
+
+	return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
+}
+
+static int pohmelfs_wait_on_page_locked(struct page *page)
+{
+	struct pohmelfs_sb *psb = POHMELFS_SB(page->mapping->host->i_sb);
+	long ret = psb->wait_on_page_timeout;
+	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
+	int err = 0;
+
+	if (!PageLocked(page))
+		return 0;
+
+	for (;;) {
+		prepare_to_wait(page_waitqueue(page),
+				&wait.wait, TASK_INTERRUPTIBLE);
+
+		dprintk("%s: page: %p, locked: %d, uptodate: %d, error: %d, flags: %lx.\n",
+				__func__, page, PageLocked(page), PageUptodate(page),
+				PageError(page), page->flags);
+
+		if (!PageLocked(page))
+			break;
+
+		if (!signal_pending(current)) {
+			ret = schedule_timeout(ret);
+			if (!ret)
+				break;
+			continue;
+		}
+		ret = -ERESTARTSYS;
+		break;
+	}
+	finish_wait(page_waitqueue(page), &wait.wait);
+
+	if (!ret)
+		err = -ETIMEDOUT;
+
+
+	if (!err)
+		SetPageUptodate(page);
+
+	dprintk("%s: page: %p, uptodate: %d, locked: %d, err: %d.\n",
+			__func__, page, PageUptodate(page), PageLocked(page), err);
+
+	return err;
+}
+
+static int pohmelfs_read_page_complete(struct page **pages, unsigned int page_num,
+		void *private, int err)
+{
+	struct page *page = private;
+	
+	if (PageChecked(page))
+		return err;
+
+	if (err < 0)
+		SetPageError(page);
+
+	unlock_page(page);
+
+	return err;
+}
+
+/*
+ * Read a page from remote server.
+ * Function will wait until page is unlocked.
+ */
+static int pohmelfs_readpage(struct file *file, struct page *page)
+{
+	struct inode *inode = page->mapping->host;
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	struct netfs_trans *t;
+	struct netfs_cmd *cmd;
+	int err, path_len;
+	void *data;
+
+	err = pohmelfs_data_lock(pi, page->index << PAGE_CACHE_SHIFT,
+			PAGE_SIZE, POHMELFS_READ_LOCK);
+	if (err)
+		goto err_out_exit;
+
+	mutex_lock(&psb->path_lock);
+	path_len = pohmelfs_path_length(pi);
+	mutex_unlock(&psb->path_lock);
+
+	if (path_len < 0) {
+		err = path_len;
+		goto err_out_exit;
+	}
+
+	t = netfs_trans_alloc(psb, path_len, NETFS_TRANS_SINGLE_DST, 0);
+	if (!t) {
+		err = -ENOMEM;
+		goto err_out_exit;
+	}
+
+	t->complete = pohmelfs_read_page_complete;
+	t->private = page;
+
+	cmd = netfs_trans_current(t);
+	data = (void *)(cmd + 1);
+
+	mutex_lock(&psb->path_lock);
+	err = pohmelfs_construct_path_string(pi, data, path_len);
+	mutex_unlock(&psb->path_lock);
+	if (err < 0)
+		goto err_out_free;
+
+	path_len = err + 1;
+
+	cmd->id = pi->ino;
+	cmd->start = page->index;
+	cmd->start <<= PAGE_CACHE_SHIFT;
+	cmd->size = PAGE_CACHE_SIZE + path_len;
+	cmd->cmd = NETFS_READ_PAGE;
+	cmd->ext = path_len;
+
+	dprintk("%s: path: '%s', page: %p, ino: %llu, start: %llu, size: %lu.\n",
+			__func__, (char *)data, page, pi->ino, cmd->start, PAGE_CACHE_SIZE);
+
+	netfs_convert_cmd(cmd);
+	netfs_trans_update(cmd, t, path_len);
+
+	err = netfs_trans_finish(t, psb);
+	if (err)
+		goto err_out_return;
+
+	return pohmelfs_wait_on_page_locked(page);
+
+err_out_free:
+	t->result = err;
+	netfs_trans_put(t);
+err_out_exit:
+	SetPageError(page);
+	if (PageLocked(page))
+		unlock_page(page);
+err_out_return:
+	printk("%s: page: %p, start: %lu, size: %lu, err: %d.\n",
+		__func__, page, page->index << PAGE_CACHE_SHIFT, PAGE_CACHE_SIZE, err);
+
+	return err;
+}
+
+/*
+ * Write begin/end magic.
+ * Allocates a page and writes inode if it was not synced to server before.
+ */
+static int pohmelfs_write_begin(struct file *file, struct address_space *mapping,
+		loff_t pos, unsigned len, unsigned flags,
+		struct page **pagep, void **fsdata)
+{
+	struct inode *inode = mapping->host;
+	struct page *page;
+	pgoff_t index;
+	unsigned start, end;
+	int err;
+
+	*pagep = NULL;
+
+	index = pos >> PAGE_CACHE_SHIFT;
+	start = pos & (PAGE_CACHE_SIZE - 1);
+	end = start + len;
+
+	page = __grab_cache_page(mapping, index);
+
+	dprintk("%s: page: %p pos: %llu, len: %u, index: %lu, start: %u, end: %u, uptodate: %d.\n",
+			__func__, page,	pos, len, index, start, end, PageUptodate(page));
+
+	if (!page) {
+		err = -ENOMEM;
+		goto err_out_exit;
+	}
+
+	while (!PageUptodate(page)) {
+		if (start && test_bit(NETFS_INODE_CREATED, &POHMELFS_I(inode)->state)) {
+			err = pohmelfs_readpage(file, page);
+			if (err)
+				goto err_out_exit;
+
+			lock_page(page);
+			continue;
+		}
+
+		if (len != PAGE_CACHE_SIZE) {
+			void *kaddr = kmap_atomic(page, KM_USER0);
+
+			memset(kaddr + start, 0, PAGE_CACHE_SIZE - start);
+			flush_dcache_page(page);
+			kunmap_atomic(kaddr, KM_USER0);
+		}
+		SetPageUptodate(page);
+	}
+
+	set_page_private(page, end);
+
+	*pagep = page;
+
+	return 0;
+
+err_out_exit:
+	page_cache_release(page);
+	*pagep = NULL;
+
+	return err;
+}
+
+static int pohmelfs_write_end(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned copied,
+			struct page *page, void *fsdata)
+{
+	struct inode *inode = mapping->host;
+
+	if (copied != len) {
+		unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+		void *kaddr = kmap_atomic(page, KM_USER0);
+
+		memset(kaddr + from + copied, 0, len - copied);
+		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
+	}
+
+	SetPageUptodate(page);
+	set_page_dirty(page);
+
+	dprintk("%s: page: %p [U: %d, D: %d, L: %d], pos: %llu, len: %u, copied: %u.\n",
+			__func__, page,
+			PageUptodate(page), PageDirty(page), PageLocked(page),
+			pos, len, copied);
+
+	flush_dcache_page(page);
+
+	unlock_page(page);
+	page_cache_release(page);
+
+	if (pos + copied > inode->i_size) {
+		struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+
+		mutex_lock(&psb->path_lock);
+		psb->avail_size -= pos + copied - inode->i_size;
+		mutex_unlock(&psb->path_lock);
+
+		i_size_write(inode, pos + copied);
+	}
+
+	return copied;
+}
+
+static int pohmelfs_readpages_trans_complete(struct page **__pages, unsigned int page_num,
+		void *private, int err)
+{
+	struct pohmelfs_inode *pi = private;
+	unsigned int i, num;
+	struct page **pages, *page = (struct page *)__pages;
+	loff_t index = page->index;
+
+	pages = kzalloc(sizeof(void *) * page_num, GFP_NOIO);
+	if (!pages)
+		return -ENOMEM;
+
+	num = find_get_pages_contig(pi->vfs_inode.i_mapping, index, page_num, pages);
+	if (num <= 0) {
+		err = num;
+		goto err_out_free;
+	}
+
+	for (i=0; i<num; ++i) {
+		page = pages[i];
+
+		if (err)
+			printk("%s: %u/%u: page: %p, index: %lu, uptodate: %d, locked: %d, err: %d.\n",
+				__func__, i, num, page, page->index,
+				PageUptodate(page), PageLocked(page), err);
+
+		if (!PageChecked(page)) {
+			if (err < 0)
+				SetPageError(page);
+			unlock_page(page);
+		}
+		page_cache_release(page);
+	}
+
+err_out_free:
+	kfree(pages);
+	return err;
+}
+
+static int pohmelfs_send_readpages(struct pohmelfs_inode *pi, struct page *first, unsigned int num)
+{
+	struct netfs_trans *t;
+	struct netfs_cmd *cmd;
+	struct pohmelfs_sb *psb = POHMELFS_SB(pi->vfs_inode.i_sb);
+	int err, path_len;
+	void *data;
+
+	err = pohmelfs_data_lock(pi, first->index << PAGE_CACHE_SHIFT,
+			num * PAGE_SIZE, POHMELFS_READ_LOCK);
+	if (err)
+		goto err_out_exit;
+
+	mutex_lock(&psb->path_lock);
+	path_len = pohmelfs_path_length(pi);
+	mutex_unlock(&psb->path_lock);
+
+	if (path_len < 0) {
+		err = path_len;
+		goto err_out_exit;
+	}
+
+	t = netfs_trans_alloc(psb, path_len, NETFS_TRANS_SINGLE_DST, 0);
+	if (!t) {
+		err = -ENOMEM;
+		goto err_out_exit;
+	}
+
+	cmd = netfs_trans_current(t);
+	data = (void *)(cmd + 1);
+
+	t->complete = pohmelfs_readpages_trans_complete;
+	t->private = pi;
+	t->page_num = num;
+	t->pages = (struct page **)first;
+
+	mutex_lock(&psb->path_lock);
+	err = pohmelfs_construct_path_string(pi, data, path_len);
+	mutex_unlock(&psb->path_lock);
+	if (err < 0)
+		goto err_out_put;
+
+	path_len = err + 1;
+
+	cmd->cmd = NETFS_READ_PAGES;
+	cmd->start = first->index;
+	cmd->start <<= PAGE_CACHE_SHIFT;
+	cmd->size = (num << 8 | PAGE_CACHE_SHIFT);
+	cmd->id = pi->ino;
+	cmd->ext = path_len;
+
+	dprintk("%s: t: %p, gen: %u, path: '%s', path_len: %u, "
+			"start: %lu, num: %u.\n",
+			__func__, t, t->gen, (char *)data, path_len,
+			first->index, num);
+
+	netfs_convert_cmd(cmd);
+	netfs_trans_update(cmd, t, path_len);
+
+	return netfs_trans_finish(t, psb);
+
+err_out_put:
+	netfs_trans_free(t);
+err_out_exit:
+	pohmelfs_readpages_trans_complete((struct page **)first, num, pi, err);
+	return err;
+}
+
+#define list_to_page(head) (list_entry((head)->prev, struct page, lru))
+
+static int pohmelfs_readpages(struct file *file, struct address_space *mapping,
+			struct list_head *pages, unsigned nr_pages)
+{
+	unsigned int page_idx, num = 0;
+	struct page *page = NULL, *first = NULL;
+
+	for (page_idx = 0; page_idx < nr_pages; page_idx++) {
+		page = list_to_page(pages);
+
+		prefetchw(&page->flags);
+		list_del(&page->lru);
+
+		if (!add_to_page_cache_lru(page, mapping,
+					page->index, GFP_KERNEL)) {
+
+			if (!num) {
+				num = 1;
+				first = page;
+				page_cache_release(page);
+				continue;
+			}
+
+			dprintk("%s: added to lru page: %p, page_index: %lu, first_index: %lu.\n",
+					__func__, page, page->index, first->index);
+
+			if (unlikely(first->index + num != page->index) || (num > 500)) {
+				pohmelfs_send_readpages(POHMELFS_I(mapping->host),
+						first, num);
+				first = page;
+				num = 0;
+			}
+
+			num++;
+		}
+		page_cache_release(page);
+	}
+	pohmelfs_send_readpages(POHMELFS_I(mapping->host), first, num);
+
+	/*
+	 * This will be sync read, so when last page is processed,
+	 * all previous are alerady unlocked and ready to be used.
+	 */
+	return 0;
+}
+
+/*
+ * Small addres space operations for POHMELFS.
+ */
+const struct address_space_operations pohmelfs_aops = {
+	.readpage		= pohmelfs_readpage,
+	.readpages		= pohmelfs_readpages,
+	.writepages		= pohmelfs_writepages,
+	.write_begin		= pohmelfs_write_begin,
+	.write_end		= pohmelfs_write_end,
+	.set_page_dirty 	= __set_page_dirty_nobuffers,
+};
+
+/*
+ * ->detroy_inode() callback. Deletes inode from the caches
+ *  and frees private data.
+ */
+static void pohmelfs_destroy_inode(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct pohmelfs_sb *psb = POHMELFS_SB(sb);
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+
+	pohmelfs_data_unlock(pi, 0, inode->i_size, POHMELFS_READ_LOCK);
+
+	pohmelfs_inode_del_inode(psb, pi);
+
+	dprintk("%s: pi: %p, inode: %p, ino: %llu.\n",
+		__func__, pi, &pi->vfs_inode, pi->ino);
+	kmem_cache_free(pohmelfs_inode_cache, pi);
+	atomic_long_dec(&psb->total_inodes);
+}
+
+/*
+ * ->alloc_inode() callback. Allocates inode and initilizes private data.
+ */
+static struct inode *pohmelfs_alloc_inode(struct super_block *sb)
+{
+	struct pohmelfs_inode *pi;
+
+	pi = kmem_cache_alloc(pohmelfs_inode_cache, GFP_NOIO);
+	if (!pi)
+		return NULL;
+
+	pi->hash_root = RB_ROOT;
+	mutex_init(&pi->offset_lock);
+
+	INIT_LIST_HEAD(&pi->sync_del_list);
+	INIT_LIST_HEAD(&pi->sync_create_list);
+
+	INIT_LIST_HEAD(&pi->inode_entry);
+
+	pi->lock_type = 0;
+	pi->state = 0;
+	pi->total_len = 0;
+	pi->drop_count = 0;
+
+	dprintk("%s: pi: %p, inode: %p.\n", __func__, pi, &pi->vfs_inode);
+
+	atomic_long_inc(&POHMELFS_SB(sb)->total_inodes);
+
+	return &pi->vfs_inode;
+}
+
+/*
+ * We want fsync() to work on POHMELFS.
+ */
+static int pohmelfs_fsync(struct file *file, struct dentry *dentry, int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct writeback_control wbc = {
+		.sync_mode = WB_SYNC_ALL,
+		.nr_to_write = 0,	/* sys_fsync did this */
+	};
+
+	return sync_inode(inode, &wbc);
+}
+
+ssize_t pohmelfs_write(struct file *file, const char __user *buf,
+		size_t len, loff_t *ppos)
+{
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };
+	struct kiocb kiocb;
+	ssize_t ret;
+	loff_t pos = *ppos;
+
+	init_sync_kiocb(&kiocb, file);
+	kiocb.ki_pos = pos;
+	kiocb.ki_left = len;
+
+	dprintk("%s: len: %u, pos: %llu.\n", __func__, len, pos);
+
+	mutex_lock(&inode->i_mutex);
+	ret = pohmelfs_data_lock(pi, pos, len, POHMELFS_WRITE_LOCK);
+	if (ret)
+		goto err_out_unlock;
+
+	ret = generic_file_aio_write_nolock(&kiocb, &iov, 1, pos);
+	*ppos = kiocb.ki_pos;
+
+	mutex_unlock(&inode->i_mutex);
+	WARN_ON(ret < 0);
+
+	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
+		ssize_t err;
+
+		err = sync_page_range(inode, mapping, pos, ret);
+		if (err < 0)
+			ret = err;
+		WARN_ON(ret < 0);
+	}
+
+	return ret;
+
+err_out_unlock:
+	mutex_unlock(&inode->i_mutex);
+	return ret;
+}
+
+const static struct file_operations pohmelfs_file_ops = {
+	.open		= generic_file_open,
+	.fsync		= pohmelfs_fsync,
+
+	.llseek		= generic_file_llseek,
+
+	.read		= do_sync_read,
+	.aio_read	= generic_file_aio_read,
+
+	.mmap		= generic_file_mmap,
+
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= generic_file_splice_write,
+
+	.write		= pohmelfs_write,
+	.aio_write	= generic_file_aio_write,
+};
+
+const struct inode_operations pohmelfs_symlink_inode_operations = {
+	.readlink	= generic_readlink,
+	.follow_link	= page_follow_link_light,
+	.put_link	= page_put_link,
+};
+
+int pohmelfs_setattr_raw(struct inode *inode, struct iattr *attr)
+{
+	int err;
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+
+	err = inode_change_ok(inode, attr);
+	if (err)
+		goto err_out_exit;
+
+	if ((attr->ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
+	    (attr->ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid)) {
+		err = DQUOT_TRANSFER(inode, attr) ? -EDQUOT : 0;
+		if (err)
+			goto err_out_exit;
+	}
+
+	err = inode_setattr(inode, attr);
+	if (err)
+		goto err_out_exit;
+
+	if (attr->ia_valid & ATTR_MODE) {
+		mutex_lock(&psb->path_lock);
+		pohmelfs_change_path_entry(psb, pi->ino, inode->i_mode);
+		mutex_unlock(&psb->path_lock);
+	}
+
+	dprintk("%s: ino: %llu, mode: %o -> %o, uid: %u -> %u, gid: %u -> %u, size: %llu -> %llu.\n",
+			__func__, pi->ino, inode->i_mode, attr->ia_mode,
+			inode->i_uid, attr->ia_uid, inode->i_gid, attr->ia_gid, inode->i_size, attr->ia_size);
+
+	return 0;
+
+err_out_exit:
+	return err;
+}
+
+int pohmelfs_setattr(struct dentry *dentry, struct iattr *attr)
+{
+	struct inode *inode = dentry->d_inode;
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	int err;
+
+	if (!(psb->state_flags & POHMELFS_FLAGS_XATTR))
+		return -EOPNOTSUPP;
+
+	err = pohmelfs_data_lock(pi, 0, ~0, POHMELFS_WRITE_LOCK);
+	if (err)
+		goto err_out_exit;
+
+	err = security_inode_setattr(dentry, attr);
+	if (err)
+		goto err_out_exit;
+
+	err = pohmelfs_setattr_raw(inode, attr);
+	if (err)
+		goto err_out_exit;
+
+	return 0;
+
+err_out_exit:
+	return err;
+}
+
+static int pohmelfs_send_xattr_req(struct pohmelfs_inode *pi, u64 id, u64 start,
+		const char *name, const void *value, size_t attrsize, int command)
+{
+	struct pohmelfs_sb *psb = POHMELFS_SB(pi->vfs_inode.i_sb);
+	int err, path_len, namelen = strlen(name) + 1; /* 0-byte */
+	struct netfs_trans *t;
+	struct netfs_cmd *cmd;
+	void *data;
+
+	dprintk("%s: id: %llu, start: %llu, name: '%s', attrsize: %u, cmd: %d.\n",
+			__func__, id, start, name, attrsize, command);
+
+	mutex_lock(&psb->path_lock);
+	path_len = pohmelfs_path_length(pi);
+	mutex_unlock(&psb->path_lock);
+	if (path_len < 0) {
+		err = path_len;
+		goto err_out_exit;
+	}
+
+	t = netfs_trans_alloc(psb, namelen + path_len + attrsize, 0, 0);
+	if (!t) {
+		err = -ENOMEM;
+		goto err_out_exit;
+	}
+
+	cmd = netfs_trans_current(t);
+	data = cmd + 1;
+
+	mutex_lock(&psb->path_lock);
+	path_len = pohmelfs_construct_path_string(pi, data, path_len);
+	mutex_unlock(&psb->path_lock);
+	if (path_len < 0) {
+		err = path_len;
+		goto err_out_put;
+	}
+	path_len++; /* 0-byte */
+	data += path_len;
+
+	/*
+	 * 'name' is a NUL-terminated string already and
+	 * 'namelen' includes 0-byte.
+	 */
+	memcpy(data, name, namelen);
+	data += namelen;
+
+	memcpy(data, value, attrsize);
+
+	cmd->cmd = command;
+	cmd->id = id;
+	cmd->start = start;
+	cmd->size = attrsize + namelen + path_len;
+	cmd->ext = path_len;
+	cmd->csize = 0;
+	cmd->cpad = 0;
+
+	netfs_convert_cmd(cmd);
+	netfs_trans_update(cmd, t, namelen + path_len + attrsize);
+
+	return netfs_trans_finish(t, psb);
+
+err_out_put:
+	t->result = err;
+	netfs_trans_put(t);
+err_out_exit:
+	return err;
+}
+
+static int pohmelfs_setxattr(struct dentry *dentry, const char *name,
+		const void *value, size_t attrsize, int flags)
+{
+	struct inode *inode = dentry->d_inode;
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+
+	return pohmelfs_send_xattr_req(pi, flags, attrsize, name,
+			value, attrsize, NETFS_XATTR_SET);
+}
+
+static ssize_t pohmelfs_getxattr(struct dentry *dentry, const char *name,
+		void *value, size_t attrsize)
+{
+	struct inode *inode = dentry->d_inode;
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	struct pohmelfs_mcache *m;
+	int err;
+	long timeout = psb->mcache_timeout;
+
+	if (!(psb->state_flags & POHMELFS_FLAGS_XATTR))
+		return -EOPNOTSUPP;
+
+	m = pohmelfs_mcache_alloc(psb, 0, attrsize, value);
+	if (IS_ERR(m))
+		return PTR_ERR(m);
+
+	dprintk("%s: ino: %llu, name: '%s', size: %zu.\n",
+			__func__, pi->ino, name, attrsize);
+
+	err = pohmelfs_send_xattr_req(pi, m->gen, attrsize, name, value, 0, NETFS_XATTR_GET);
+	if (err)
+		goto err_out_put;
+
+	do {
+		err = wait_for_completion_timeout(&m->complete, timeout);
+		if (err) {
+			err = m->err;
+			break;
+		}
+
+		/*
+		 * This loop is a bit ugly, since it waits until reference counter
+		 * hits 1 and then put object here. Main goal is to prevent race with
+		 * network thread, when it can start processing given request, i.e.
+		 * increase its reference counter but yet not complete it, while
+		 * we will exit from ->getxattr() with timeout, and although request
+		 * will not be freed (its reference counter was increased by network
+		 * thread), data pointer provided by user may be released, so we will
+		 * overwrite already freed area in network thread.
+		 *
+		 * Now after timeout we remove request from the cache, so it can not be
+		 * found by network thread, and wait for its reference counter to hit 1,
+		 * i.e. if network thread already started to process this request, we wait
+		 * it to finish, and then free object locally. If reference counter is
+		 * already 1, i.e. request is not used by anyone else, we can free it without
+		 * problem.
+		 */
+		err = -ETIMEDOUT;
+		timeout = HZ;
+
+		pohmelfs_mcache_remove_locked(psb, m);
+	} while (atomic_read(&m->refcnt) != 1);
+
+	pohmelfs_mcache_put(psb, m);
+
+	dprintk("%s: ino: %llu, err: %d.\n", __func__, pi->ino, err);
+
+	return err;
+
+err_out_put:
+	pohmelfs_mcache_put(psb, m);
+	return err;
+}
+
+static int pohmelfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+	struct inode *inode = dentry->d_inode;
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+	int err;
+
+	err = pohmelfs_data_lock(pi, 0, ~0, POHMELFS_READ_LOCK);
+	if (err)
+		return err;
+
+	dprintk("%s: ino: %llu, mode: %o, uid: %u, gid: %u, size: %llu.\n",
+			__func__, pi->ino, inode->i_mode, inode->i_uid,
+			inode->i_gid, inode->i_size);
+
+	generic_fillattr(inode, stat);
+	return 0;
+}
+
+const struct inode_operations pohmelfs_file_inode_operations = {
+	.setattr	= pohmelfs_setattr,
+	.getattr	= pohmelfs_getattr,
+	.setxattr	= pohmelfs_setxattr,
+	.getxattr	= pohmelfs_getxattr,
+};
+
+/*
+ * Fill inode data: mode, size, operation callbacks and so on...
+ */
+void pohmelfs_fill_inode(struct inode *inode, struct netfs_inode_info *info)
+{
+	inode->i_mode = info->mode;
+	inode->i_nlink = info->nlink;
+	inode->i_uid = info->uid;
+	inode->i_gid = info->gid;
+	inode->i_blocks = info->blocks;
+	inode->i_rdev = info->rdev;
+	inode->i_size = info->size;
+	inode->i_version = info->version;
+	inode->i_blkbits = ffs(info->blocksize);
+
+	dprintk("%s: inode: %p, num: %lu/%llu inode is regular: %d, dir: %d, link: %d, mode: %o, size: %llu.\n",
+			__func__, inode, inode->i_ino, info->ino,
+			S_ISREG(inode->i_mode), S_ISDIR(inode->i_mode),
+			S_ISLNK(inode->i_mode), inode->i_mode, inode->i_size);
+
+	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
+
+	/*
+	 * i_mapping is a pointer to i_data during inode initialization.
+	 */
+	inode->i_data.a_ops = &pohmelfs_aops;
+
+	if (S_ISREG(inode->i_mode)) {
+		inode->i_fop = &pohmelfs_file_ops;
+		inode->i_op = &pohmelfs_file_inode_operations;
+	} else if (S_ISDIR(inode->i_mode)) {
+		inode->i_fop = &pohmelfs_dir_fops;
+		inode->i_op = &pohmelfs_dir_inode_ops;
+	} else if (S_ISLNK(inode->i_mode)) {
+		inode->i_op = &pohmelfs_symlink_inode_operations;
+		inode->i_fop = &pohmelfs_file_ops;
+	} else {
+		inode->i_fop = &generic_ro_fops;
+	}
+}
+
+static void pohmelfs_drop_inode(struct inode *inode)
+{
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	struct pohmelfs_inode *pi = POHMELFS_I(inode);
+
+	spin_lock(&psb->ino_lock);
+	list_del_init(&pi->inode_entry);
+	spin_unlock(&psb->ino_lock);
+
+	generic_drop_inode(inode);
+}
+
+static struct pohmelfs_inode *pohmelfs_get_inode_from_list(struct pohmelfs_sb *psb,
+		struct list_head *head, unsigned int *count)
+{
+	struct pohmelfs_inode *pi = NULL;
+
+	spin_lock(&psb->ino_lock);
+	if (!list_empty(head)) {
+		pi = list_entry(head->next, struct pohmelfs_inode,
+					inode_entry);
+		list_del_init(&pi->inode_entry);
+		*count = pi->drop_count;
+		pi->drop_count = 0;
+	}
+	spin_unlock(&psb->ino_lock);
+
+	return pi;
+}
+
+static void pohmelfs_flush_transactions(struct pohmelfs_sb *psb)
+{
+	struct pohmelfs_config *c;
+
+	mutex_lock(&psb->state_lock);
+	list_for_each_entry(c, &psb->state_list, config_entry) {
+		pohmelfs_state_flush_transactions(&c->state);
+	}
+	mutex_unlock(&psb->state_lock);
+}
+
+/*
+ * ->put_super() callback. Invoked before superblock is destroyed,
+ *  so it has to clean all private data.
+ */
+static void pohmelfs_put_super(struct super_block *sb)
+{
+	struct pohmelfs_sb *psb = POHMELFS_SB(sb);
+	struct rb_node *rb_node;
+	struct pohmelfs_path_entry *e;
+	struct pohmelfs_inode *pi;
+	unsigned int count;
+	unsigned int in_drop_list = 0;
+	struct inode *inode, *tmp;
+
+	dprintk("%s.\n", __func__);
+
+	/*
+	 * Kill pending transactions, which could affect inodes in-flight.
+	 */
+	pohmelfs_flush_transactions(psb);
+
+	while ((pi = pohmelfs_get_inode_from_list(psb, &psb->drop_list, &count))) {
+		inode = &pi->vfs_inode;
+
+		dprintk("%s: ino: %llu, pi: %p, inode: %p, count: %u.\n",
+				__func__, pi->ino, pi, inode, count);
+
+		if (atomic_read(&inode->i_count) != count) {
+			printk("%s: ino: %llu, pi: %p, inode: %p, count: %u, i_count: %d.\n",
+					__func__, pi->ino, pi, inode, count,
+					atomic_read(&inode->i_count));
+			count = atomic_read(&inode->i_count);
+			in_drop_list++;
+		}
+
+		while (count--)
+			iput(&pi->vfs_inode);
+	}
+
+	list_for_each_entry_safe(inode, tmp, &sb->s_inodes, i_sb_list) {
+		pi = POHMELFS_I(inode);
+
+		dprintk("%s: ino: %llu, pi: %p, inode: %p, i_count: %u.\n",
+				__func__, pi->ino, pi, inode, atomic_read(&inode->i_count));
+
+		/*
+		 * These are special inodes, they were created during
+		 * directory reading or lookup, and were not bound to dentry,
+		 * so they live here with reference counter being 1 and prevent
+		 * umount from succeed since it believes that they are busy.
+		 */
+		count = atomic_read(&inode->i_count);
+		if (count) {
+			list_del_init(&inode->i_sb_list);
+			while (count--)
+				iput(&pi->vfs_inode);
+		}
+	}
+
+	psb->trans_scan_timeout = psb->drop_scan_timeout = 0;
+	cancel_rearming_delayed_work(&psb->dwork);
+	cancel_rearming_delayed_work(&psb->drop_dwork);
+	flush_scheduled_work();
+
+	dprintk("%s: stopped workqueues.\n", __func__);
+
+	pohmelfs_crypto_exit(psb);
+	pohmelfs_state_exit(psb);
+
+	for (rb_node = rb_first(&psb->path_root); rb_node; ) {
+		e = rb_entry(rb_node, struct pohmelfs_path_entry, path_entry);
+		rb_node = rb_next(rb_node);
+
+		pohmelfs_remove_path_entry(psb, e);
+	}
+
+	kfree(psb);
+	sb->s_fs_info = NULL;
+}
+
+static int pohmelfs_remount(struct super_block *sb, int *flags, char *data)
+{
+	*flags |= MS_RDONLY;
+	return 0;
+}
+
+static int pohmelfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct super_block *sb = dentry->d_sb;
+	struct pohmelfs_sb *psb = POHMELFS_SB(sb);
+
+	/*
+	 * There are no filesystem size limits yet.
+	 */
+	memset(buf, 0, sizeof(struct kstatfs));
+
+	buf->f_type = POHMELFS_MAGIC_NUM; /* 'POH.' */
+	buf->f_bsize = sb->s_blocksize;
+	buf->f_files = psb->ino;
+	buf->f_namelen = 255;
+	buf->f_files = atomic_long_read(&psb->total_inodes);
+	buf->f_bfree = buf->f_bavail = psb->avail_size >> PAGE_SHIFT;
+	buf->f_blocks = psb->total_size >> PAGE_SHIFT;
+
+	dprintk("%s: total: %llu, avail: %llu, inodes: %llu, bsize: %lu.\n",
+		__func__, psb->total_size, psb->avail_size, buf->f_files, sb->s_blocksize);
+
+	return 0;
+}
+
+static int pohmelfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+	struct pohmelfs_sb *psb = POHMELFS_SB(vfs->mnt_sb);
+
+	seq_printf(seq, ",idx=%u", psb->idx);
+	seq_printf(seq, ",trans_scan_timeout=%u", jiffies_to_msecs(psb->trans_scan_timeout));
+	seq_printf(seq, ",drop_scan_timeout=%u", jiffies_to_msecs(psb->drop_scan_timeout));
+	seq_printf(seq, ",wait_on_page_timeout=%u", jiffies_to_msecs(psb->wait_on_page_timeout));
+	seq_printf(seq, ",trans_retries=%u", psb->trans_retries);
+	seq_printf(seq, ",crypto_thread_num=%u", psb->crypto_thread_num);
+	seq_printf(seq, ",trans_max_pages=%u", psb->trans_max_pages);
+	seq_printf(seq, ",mcache_timeout=%u", jiffies_to_msecs(psb->mcache_timeout));
+	if (psb->crypto_fail_unsupported)
+		seq_printf(seq, ",crypto_fail_unsupported");
+
+	return 0;
+}
+
+static const struct super_operations pohmelfs_sb_ops = {
+	.alloc_inode	= pohmelfs_alloc_inode,
+	.destroy_inode	= pohmelfs_destroy_inode,
+	.drop_inode	= pohmelfs_drop_inode,
+	.write_inode	= pohmelfs_write_inode,
+	.put_super	= pohmelfs_put_super,
+	.remount_fs	= pohmelfs_remount,
+	.statfs		= pohmelfs_statfs,
+	.show_options	= pohmelfs_show_options,
+};
+
+enum {
+	pohmelfs_opt_idx,
+	pohmelfs_opt_trans_scan_timeout,
+	pohmelfs_opt_drop_scan_timeout,
+	pohmelfs_opt_wait_on_page_timeout,
+	pohmelfs_opt_trans_retries,
+	pohmelfs_opt_crypto_thread_num,
+	pohmelfs_opt_trans_max_pages,
+	pohmelfs_opt_crypto_fail_unsupported,
+	pohmelfs_opt_mcache_timeout,
+};
+
+static struct match_token pohmelfs_tokens[] = {
+	{pohmelfs_opt_idx, "idx=%u"},
+	{pohmelfs_opt_trans_scan_timeout, "trans_scan_timeout=%u"},
+	{pohmelfs_opt_drop_scan_timeout, "drop_scan_timeout=%u"},
+	{pohmelfs_opt_wait_on_page_timeout, "wait_on_page_timeout=%u"},
+	{pohmelfs_opt_trans_retries, "trans_retries=%u"},
+	{pohmelfs_opt_crypto_thread_num, "crypto_thread_num=%u"},
+	{pohmelfs_opt_trans_max_pages, "trans_max_pages=%u"},
+	{pohmelfs_opt_crypto_fail_unsupported, "crypto_fail_unsupported"},
+	{pohmelfs_opt_mcache_timeout, "mcache_timeout=%u"},
+};
+
+static int pohmelfs_parse_options(char *options, struct pohmelfs_sb *psb)
+{
+	char *p;
+	substring_t args[MAX_OPT_ARGS];
+	int option, err;
+
+	if (!options)
+		return 0;
+
+	while ((p = strsep(&options, ",")) != NULL) {
+		int token;
+		if (!*p)
+			continue;
+
+		token = match_token(p, pohmelfs_tokens, args);
+
+		err = match_int(&args[0], &option);
+		if (err)
+			return err;
+
+		switch (token) {
+			case pohmelfs_opt_idx:
+				psb->idx = option;
+				break;
+			case pohmelfs_opt_trans_scan_timeout:
+				psb->trans_scan_timeout = msecs_to_jiffies(option);
+				break;
+			case pohmelfs_opt_drop_scan_timeout:
+				psb->drop_scan_timeout = msecs_to_jiffies(option);
+				break;
+			case pohmelfs_opt_wait_on_page_timeout:
+				psb->wait_on_page_timeout = msecs_to_jiffies(option);
+				break;
+			case pohmelfs_opt_mcache_timeout:
+				psb->mcache_timeout = msecs_to_jiffies(option);
+				break;
+			case pohmelfs_opt_trans_retries:
+				psb->trans_retries = option;
+				break;
+			case pohmelfs_opt_crypto_thread_num:
+				psb->crypto_thread_num = option;
+				break;
+			case pohmelfs_opt_trans_max_pages:
+				psb->trans_max_pages = option;
+				break;
+			case pohmelfs_opt_crypto_fail_unsupported:
+				psb->crypto_fail_unsupported = 1;
+				break;
+			default:
+				return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static void pohmelfs_flush_inode(struct pohmelfs_inode *pi, unsigned int count)
+{
+	struct inode *inode = &pi->vfs_inode;
+
+	dprintk("%s: %p: ino: %llu, owned: %d.\n",
+		__func__, inode, pi->ino, test_bit(NETFS_INODE_OWNED, &pi->state));
+
+	mutex_lock(&inode->i_mutex);
+	if (test_and_clear_bit(NETFS_INODE_OWNED, &pi->state)) {
+		filemap_fdatawrite(inode->i_mapping);
+		inode->i_sb->s_op->write_inode(inode, 0);
+	}
+
+	truncate_inode_pages(inode->i_mapping, 0);
+
+	pohmelfs_data_unlock(pi, 0, ~0, POHMELFS_WRITE_LOCK);
+	mutex_unlock(&inode->i_mutex);
+}
+
+static void pohmelfs_put_inode_count(struct pohmelfs_inode *pi, unsigned int count)
+{
+	dprintk("%s: ino: %llu, pi: %p, inode: %p, count: %u.\n",
+			__func__, pi->ino, pi, &pi->vfs_inode, count);
+
+	if (test_and_clear_bit(NETFS_INODE_NEED_FLUSH, &pi->state))
+		pohmelfs_flush_inode(pi, count);
+
+	while (count--)
+		iput(&pi->vfs_inode);
+}
+
+static void pohmelfs_drop_scan(struct work_struct *work)
+{
+	struct pohmelfs_sb *psb =
+		container_of(work, struct pohmelfs_sb, drop_dwork.work);
+	struct pohmelfs_inode *pi;
+	unsigned int count = 0;
+
+	while ((pi = pohmelfs_get_inode_from_list(psb, &psb->drop_list, &count))) {
+		pohmelfs_put_inode_count(pi, count);
+	}
+	pohmelfs_check_states(psb);
+
+	if (psb->drop_scan_timeout)
+		schedule_delayed_work(&psb->drop_dwork, psb->drop_scan_timeout);
+}
+
+/*
+ * Run through all transactions starting from the oldest,
+ * drop transaction from current state and try to send it
+ * to all remote nodes, which are currently installed.
+ */
+static void pohmelfs_trans_scan_state(struct netfs_state *st)
+{
+	struct rb_node *rb_node;
+	struct netfs_trans_dst *dst;
+	struct pohmelfs_sb *psb = st->psb;
+	unsigned int timeout = psb->trans_scan_timeout;
+	struct netfs_trans *t;
+	int err;
+
+	mutex_lock(&st->trans_lock);
+	for (rb_node = rb_first(&st->trans_root); rb_node; ) {
+		dst = rb_entry(rb_node, struct netfs_trans_dst, state_entry);
+		t = dst->trans;
+
+		if (timeout && time_after(dst->send_time + timeout, jiffies)
+				&& dst->retries == 0)
+			break;
+
+		dprintk("%s: t: %p, gen: %u, st: %p, retries: %u, max: %u.\n",
+			__func__, t, t->gen, st, dst->retries, psb->trans_retries);
+		netfs_trans_get(t);
+
+		rb_node = rb_next(rb_node);
+
+		err = -ETIMEDOUT;
+		if (timeout && (++dst->retries < psb->trans_retries)) {
+			err = netfs_trans_resend(t, psb);
+		}
+
+		if (err || (t->flags & NETFS_TRANS_SINGLE_DST)) {
+			netfs_trans_remove_nolock(dst, st);
+			netfs_trans_drop_dst_nostate(dst);
+		}
+
+		t->result = err;
+		netfs_trans_put(t);
+	}
+	mutex_unlock(&st->trans_lock);
+}
+
+/*
+ * Walk through all installed network states and resend all
+ * transactions, which are old enough.
+ */
+static void pohmelfs_trans_scan(struct work_struct *work)
+{
+	struct pohmelfs_sb *psb =
+		container_of(work, struct pohmelfs_sb, dwork.work);
+	struct netfs_state *st;
+	struct pohmelfs_config *c;
+
+	mutex_lock(&psb->state_lock);
+	list_for_each_entry(c, &psb->state_list, config_entry) {
+		st = &c->state;
+
+		pohmelfs_trans_scan_state(st);
+	}
+	mutex_unlock(&psb->state_lock);
+
+	/*
+	 * If no timeout specified then system is in the middle of umount process,
+	 * so no need to reschedule scanning process again.
+	 */
+	if (psb->trans_scan_timeout)
+		schedule_delayed_work(&psb->dwork, psb->trans_scan_timeout);
+}
+
+int pohmelfs_meta_command_data(struct pohmelfs_inode *pi, u64 id, unsigned int cmd_op, char *addon,
+		unsigned int flags, netfs_trans_complete_t complete, void *priv, u64 start)
+{
+	struct inode *inode = &pi->vfs_inode;
+	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
+	int err, sz, diff;
+	struct netfs_trans *t;
+	unsigned int path_len, addon_len = 0;
+	void *data;
+	struct netfs_inode_info *info;
+	struct netfs_cmd *cmd;
+
+	dprintk("%s: ino: %llu, cmd: %u, addon: %p.\n", __func__, pi->ino, cmd_op, addon);
+	
+	mutex_lock(&psb->path_lock);
+	sz = path_len = pohmelfs_path_length(pi);
+	mutex_unlock(&psb->path_lock);
+
+	if (path_len < 0) {
+		err = path_len;
+		goto err_out_exit;
+	}
+
+	if (addon)
+		addon_len = strlen(addon) + 1; /* 0-byte */
+	sz += addon_len;
+
+	if (cmd_op == NETFS_INODE_INFO)
+		sz += sizeof(struct netfs_inode_info);
+
+	t = netfs_trans_alloc(psb, sz, flags, 0);
+	if (!t) {
+		err = -ENOMEM;
+		goto err_out_exit;
+	}
+	t->complete = complete;
+	t->private = priv;
+
+	cmd = netfs_trans_current(t);
+	data = (void *)(cmd + 1);
+
+	if (cmd_op == NETFS_INODE_INFO) {
+		info = (struct netfs_inode_info *)(cmd + 1);
+		data = (void *)(info + 1);
+
+		/*
+		 * We are under i_mutex, can read and change whatever we want...
+		 */
+		info->mode = inode->i_mode;
+		info->nlink = inode->i_nlink;
+		info->uid = inode->i_uid;
+		info->gid = inode->i_gid;
+		info->blocks = inode->i_blocks;
+		info->rdev = inode->i_rdev;
+		info->size = inode->i_size;
+		info->version = inode->i_version;
+
+		netfs_convert_inode_info(info);
+	}
+
+	mutex_lock(&psb->path_lock);
+	err = pohmelfs_construct_path_string(pi, data, path_len);
+	mutex_unlock(&psb->path_lock);
+	if (err < 0)
+		goto err_out_free;
+
+	dprintk("%s: err: %d, path_len: %d.\n", __func__, err, path_len);
+
+	diff = err + 1 - path_len;
+	sz += diff;
+	path_len += diff;
+
+	if (addon)
+		path_len += sprintf(data + err, "/%s", addon) + 1 /* 0 - byte */;
+
+	cmd->cmd = cmd_op;
+	cmd->ext = path_len;
+	cmd->size = sz;
+	cmd->id = id;
+	cmd->start = start;
+
+	netfs_convert_cmd(cmd);
+	netfs_trans_update(cmd, t, sz);
+
+	/*
+	 * Note, that it is possible to leak error here: transaction callback will not
+	 * be invoked for allocation path failure.
+	 */
+	return netfs_trans_finish(t, psb);
+
+err_out_free:
+	netfs_trans_free(t);
+err_out_exit:
+	if (complete)
+		complete(NULL, 0, priv, err);
+	return err;
+}
+
+int pohmelfs_meta_command(struct pohmelfs_inode *pi, unsigned int cmd_op, unsigned int flags,
+		netfs_trans_complete_t complete, void *priv, u64 start)
+{
+	return pohmelfs_meta_command_data(pi, pi->ino, cmd_op, NULL, flags, complete, priv, start);
+}
+
+/*
+ * Send request and wait for POHMELFS root capabilities response,
+ * which will update server's informaion about size of the export,
+ * permissions, number of objects, available size and so on.
+ */
+static int pohmelfs_root_handshake(struct pohmelfs_sb *psb)
+{
+	struct netfs_trans *t;
+	struct netfs_cmd *cmd;
+	int err = -ENOMEM;
+
+	t = netfs_trans_alloc(psb, 0, 0, 0);
+	if (!t)
+		goto err_out_exit;
+
+	cmd = netfs_trans_current(t);
+
+	cmd->cmd = NETFS_CAPABILITIES;
+	cmd->id = POHMELFS_ROOT_CAPABILITIES;
+	cmd->size = 0;
+	cmd->start = 0;
+	cmd->ext = 0;
+	cmd->csize = 0;
+
+	netfs_convert_cmd(cmd);
+	netfs_trans_update(cmd, t, 0);
+
+	err = netfs_trans_finish(t, psb);
+	if (err)
+		goto err_out_exit;
+
+	psb->flags = ~0;
+	err = wait_event_interruptible_timeout(psb->wait,
+			(psb->flags != ~0),
+			psb->wait_on_page_timeout);
+	if (!err) {
+		err = -ETIMEDOUT;
+	} else {
+		err = -psb->flags;
+	}
+
+	if (err)
+		goto err_out_exit;
+
+	return 0;
+
+err_out_exit:
+	return err;
+}
+
+/*
+ * Allocate private superblock and create root dir.
+ */
+static int pohmelfs_fill_super(struct super_block *sb, void *data, int silent)
+{
+	struct pohmelfs_sb *psb;
+	int err = -ENOMEM;
+	struct inode *root;
+	struct pohmelfs_inode *npi;
+	struct qstr str;
+
+	psb = kzalloc(sizeof(struct pohmelfs_sb), GFP_KERNEL);
+	if (!psb)
+		goto err_out_exit;
+
+	sb->s_fs_info = psb;
+	sb->s_op = &pohmelfs_sb_ops;
+	sb->s_magic = POHMELFS_MAGIC_NUM;
+	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	sb->s_blocksize = PAGE_SIZE;
+
+	psb->sb = sb;
+	psb->path_root = RB_ROOT;
+
+	psb->ino = 2;
+	psb->idx = 0;
+	psb->active_state = NULL;
+	psb->trans_retries = 5;
+	psb->trans_data_size = PAGE_SIZE;
+	psb->drop_scan_timeout = msecs_to_jiffies(1000);
+	psb->trans_scan_timeout = msecs_to_jiffies(5000);
+	psb->wait_on_page_timeout = msecs_to_jiffies(5000);
+	init_waitqueue_head(&psb->wait);
+
+	spin_lock_init(&psb->ino_lock);
+
+	mutex_init(&psb->path_lock);
+	INIT_LIST_HEAD(&psb->drop_list);
+	
+	mutex_init(&psb->mcache_lock);
+	psb->mcache_root = RB_ROOT;
+	psb->mcache_timeout = msecs_to_jiffies(5000);
+	atomic_long_set(&psb->mcache_gen, 0);
+
+	psb->trans_max_pages = 100;
+
+	psb->crypto_align_size = 16;
+	psb->crypto_attached_size = 0;
+	psb->hash_strlen = 0;
+	psb->cipher_strlen = 0;
+	psb->perform_crypto = 0;
+	psb->crypto_thread_num = 2;
+	psb->crypto_fail_unsupported = 0;
+	mutex_init(&psb->crypto_thread_lock);
+	INIT_LIST_HEAD(&psb->crypto_ready_list);
+	INIT_LIST_HEAD(&psb->crypto_active_list);
+
+	atomic_set(&psb->trans_gen, 1);
+	atomic_set(&psb->total_inodes, 0);
+
+	mutex_init(&psb->state_lock);
+	INIT_LIST_HEAD(&psb->state_list);
+
+	err = pohmelfs_parse_options((char *) data, psb);
+	if (err)
+		goto err_out_free_sb;
+
+	err = pohmelfs_copy_crypto(psb);
+	if (err)
+		goto err_out_free_sb;
+
+	err = pohmelfs_state_init(psb);
+	if (err)
+		goto err_out_free_strings;
+
+	err = pohmelfs_crypto_init(psb);
+	if (err)
+		goto err_out_state_exit;
+
+	err = pohmelfs_root_handshake(psb);
+	if (err)
+		goto err_out_crypto_exit;
+
+	str.name = "/";
+	str.hash = jhash("/", 1, 0);
+	str.len = 1;
+
+	npi = pohmelfs_create_entry_local(psb, NULL, &str, 0, 0755|S_IFDIR);
+	if (IS_ERR(npi)) {
+		err = PTR_ERR(npi);
+		goto err_out_crypto_exit;
+	}
+	set_bit(NETFS_INODE_CREATED, &npi->state);
+	clear_bit(NETFS_INODE_REMOTE_SYNCED, &npi->state);
+
+	root = &npi->vfs_inode;
+
+	sb->s_root = d_alloc_root(root);
+	if (!sb->s_root)
+		goto err_out_put_root;
+	
+	INIT_DELAYED_WORK(&psb->drop_dwork, pohmelfs_drop_scan);
+	schedule_delayed_work(&psb->drop_dwork, psb->drop_scan_timeout);
+
+	INIT_DELAYED_WORK(&psb->dwork, pohmelfs_trans_scan);
+	schedule_delayed_work(&psb->dwork, psb->trans_scan_timeout);
+
+	return 0;
+
+err_out_put_root:
+	iput(root);
+err_out_crypto_exit:
+	pohmelfs_crypto_exit(psb);
+err_out_state_exit:
+	pohmelfs_state_exit(psb);
+err_out_free_strings:
+	kfree(psb->cipher_string);
+	kfree(psb->hash_string);
+err_out_free_sb:
+	kfree(psb);
+err_out_exit:
+
+	dprintk("%s: err: %d.\n", __func__, err);
+	return err;
+}
+
+/*
+ * Some VFS magic here...
+ */
+static int pohmelfs_get_sb(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
+{
+	return get_sb_nodev(fs_type, flags, data, pohmelfs_fill_super,
+				mnt);
+}
+
+static struct file_system_type pohmel_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "pohmel",
+	.get_sb		= pohmelfs_get_sb,
+	.kill_sb 	= kill_anon_super,
+};
+
+/*
+ * Cache and module initializations and freeing routings.
+ */
+static void pohmelfs_init_once(void *data)
+{
+	struct pohmelfs_inode *pi = data;
+
+	inode_init_once(&pi->vfs_inode);
+}
+
+static int __init pohmelfs_init_inodecache(void)
+{
+	pohmelfs_inode_cache = kmem_cache_create("pohmelfs_inode_cache",
+				sizeof(struct pohmelfs_inode),
+				0, (SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD),
+				pohmelfs_init_once);
+	if (!pohmelfs_inode_cache)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void pohmelfs_destroy_inodecache(void)
+{
+	kmem_cache_destroy(pohmelfs_inode_cache);
+}
+
+static int __init init_pohmel_fs(void)
+{
+	int err;
+
+	err = pohmelfs_config_init();
+	if (err)
+		goto err_out_exit;
+
+	err = pohmelfs_init_inodecache();
+	if (err)
+		goto err_out_config_exit;
+
+	err = pohmelfs_mcache_init();
+	if (err)
+		goto err_out_destroy;
+
+	err = netfs_trans_init();
+	if (err)
+		goto err_out_mcache_exit;
+
+	err = register_filesystem(&pohmel_fs_type);
+	if (err)
+		goto err_out_trans;
+
+	return 0;
+
+err_out_trans:
+	netfs_trans_exit();
+err_out_mcache_exit:
+	pohmelfs_mcache_exit();
+err_out_destroy:
+	pohmelfs_destroy_inodecache();
+err_out_config_exit:
+	pohmelfs_config_exit();
+err_out_exit:
+	return err;
+}
+
+static void __exit exit_pohmel_fs(void)
+{
+        unregister_filesystem(&pohmel_fs_type);
+	pohmelfs_destroy_inodecache();
+	pohmelfs_mcache_exit();
+	pohmelfs_config_exit();
+	netfs_trans_exit();
+}
+
+module_init(init_pohmel_fs);
+module_exit(exit_pohmel_fs);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Evgeniy Polyakov <zbr@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("Pohmel filesystem");
--
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