write.c

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	mark_inode_dirty(inode);
}
#endif

/*
 * Wait for a request to complete.
 *
 * Interruptible by signals only if mounted with intr flag.
 */
static int
nfs_wait_on_requests(struct inode *inode, struct file *file, unsigned long idx_start, unsigned int npages)
{
	struct list_head	*p, *head;
	unsigned long		idx_end;
	unsigned int		res = 0;
	int			error;

	if (npages == 0)
		idx_end = ~0;
	else
		idx_end = idx_start + npages - 1;

	head = &inode->u.nfs_i.writeback;
 restart:
	spin_lock(&nfs_wreq_lock);
	list_for_each_prev(p, head) {
		unsigned long pg_idx;
		struct nfs_page *req = nfs_inode_wb_entry(p);

		if (file && req->wb_file != file)
			continue;

		pg_idx = page_index(req->wb_page);
		if (pg_idx < idx_start)
			break;
		if (pg_idx > idx_end)
			continue;

		if (!NFS_WBACK_BUSY(req))
			continue;
		req->wb_count++;
		spin_unlock(&nfs_wreq_lock);
		error = nfs_wait_on_request(req);
		nfs_release_request(req);
		if (error < 0)
			return error;
		res++;
		goto restart;
	}
	spin_unlock(&nfs_wreq_lock);
	return res;
}

/**
 * nfs_scan_lru_dirty_timeout - Scan LRU list for timed out dirty requests
 * @server: NFS superblock data
 * @dst: destination list
 *
 * Moves a maximum of 'wpages' requests from the NFS dirty page LRU list.
 * The elements are checked to ensure that they form a contiguous set
 * of pages, and that they originated from the same file.
 */
int
nfs_scan_lru_dirty_timeout(struct nfs_server *server, struct list_head *dst)
{
	struct inode *inode;
	int npages;

	npages = nfs_scan_lru_timeout(&server->lru_dirty, dst, server->wpages);
	if (npages) {
		inode = nfs_list_entry(dst->next)->wb_inode;
		inode->u.nfs_i.ndirty -= npages;
	}
	return npages;
}

/**
 * nfs_scan_lru_dirty - Scan LRU list for dirty requests
 * @server: NFS superblock data
 * @dst: destination list
 *
 * Moves a maximum of 'wpages' requests from the NFS dirty page LRU list.
 * The elements are checked to ensure that they form a contiguous set
 * of pages, and that they originated from the same file.
 */
int
nfs_scan_lru_dirty(struct nfs_server *server, struct list_head *dst)
{
	struct inode *inode;
	int npages;

	npages = nfs_scan_lru(&server->lru_dirty, dst, server->wpages);
	if (npages) {
		inode = nfs_list_entry(dst->next)->wb_inode;
		inode->u.nfs_i.ndirty -= npages;
	}
	return npages;
}

/*
 * nfs_scan_dirty - Scan an inode for dirty requests
 * @inode: NFS inode to scan
 * @dst: destination list
 * @file: if set, ensure we match requests from this file
 * @idx_start: lower bound of page->index to scan.
 * @npages: idx_start + npages sets the upper bound to scan.
 *
 * Moves requests from the inode's dirty page list.
 * The requests are *not* checked to ensure that they form a contiguous set.
 */
static int
nfs_scan_dirty(struct inode *inode, struct list_head *dst, struct file *file, unsigned long idx_start, unsigned int npages)
{
	int	res;
	res = nfs_scan_list(&inode->u.nfs_i.dirty, dst, file, idx_start, npages);
	inode->u.nfs_i.ndirty -= res;
	if ((inode->u.nfs_i.ndirty == 0) != list_empty(&inode->u.nfs_i.dirty))
		printk(KERN_ERR "NFS: desynchronized value of nfs_i.ndirty.\n");
	return res;
}

#ifdef CONFIG_NFS_V3
/**
 * nfs_scan_lru_commit_timeout - Scan LRU list for timed out commit requests
 * @server: NFS superblock data
 * @dst: destination list
 *
 * Finds the first a timed out request in the NFS commit LRU list and moves it
 * to the list dst. If such an element is found, we move all other commit
 * requests that apply to the same inode.
 * The assumption is that doing everything in a single commit-to-disk is
 * the cheaper alternative.
 */
int
nfs_scan_lru_commit_timeout(struct nfs_server *server, struct list_head *dst)
{
	struct inode *inode;
	int npages;

	npages = nfs_scan_lru_timeout(&server->lru_commit, dst, 1);
	if (npages) {
		inode = nfs_list_entry(dst->next)->wb_inode;
		npages += nfs_scan_list(&inode->u.nfs_i.commit, dst, NULL, 0, 0);
		inode->u.nfs_i.ncommit -= npages;
	}
	return npages;
}


/**
 * nfs_scan_lru_commit_timeout - Scan LRU list for timed out commit requests
 * @server: NFS superblock data
 * @dst: destination list
 *
 * Finds the first request in the NFS commit LRU list and moves it
 * to the list dst. If such an element is found, we move all other commit
 * requests that apply to the same inode.
 * The assumption is that doing everything in a single commit-to-disk is
 * the cheaper alternative.
 */
int
nfs_scan_lru_commit(struct nfs_server *server, struct list_head *dst)
{
	struct inode *inode;
	int npages;

	npages = nfs_scan_lru(&server->lru_commit, dst, 1);
	if (npages) {
		inode = nfs_list_entry(dst->next)->wb_inode;
		npages += nfs_scan_list(&inode->u.nfs_i.commit, dst, NULL, 0, 0);
		inode->u.nfs_i.ncommit -= npages;
	}
	return npages;
}

/*
 * nfs_scan_commit - Scan an inode for commit requests
 * @inode: NFS inode to scan
 * @dst: destination list
 * @file: if set, ensure we collect requests from this file only.
 * @idx_start: lower bound of page->index to scan.
 * @npages: idx_start + npages sets the upper bound to scan.
 *
 * Moves requests from the inode's 'commit' request list.
 * The requests are *not* checked to ensure that they form a contiguous set.
 */
static int
nfs_scan_commit(struct inode *inode, struct list_head *dst, struct file *file, unsigned long idx_start, unsigned int npages)
{
	int	res;
	res = nfs_scan_list(&inode->u.nfs_i.commit, dst, file, idx_start, npages);
	inode->u.nfs_i.ncommit -= res;
	if ((inode->u.nfs_i.ncommit == 0) != list_empty(&inode->u.nfs_i.commit))
		printk(KERN_ERR "NFS: desynchronized value of nfs_i.ncommit.\n");
	return res;
}
#endif


/*
 * Try to update any existing write request, or create one if there is none.
 * In order to match, the request's credentials must match those of
 * the calling process.
 *
 * Note: Should always be called with the Page Lock held!
 */
static struct nfs_page *
nfs_update_request(struct file* file, struct inode *inode, struct page *page,
		   unsigned int offset, unsigned int bytes)
{
	struct nfs_page		*req, *new = NULL;
	unsigned long		rqend, end;

	end = offset + bytes;

	for (;;) {
		/* Loop over all inode entries and see if we find
		 * A request for the page we wish to update
		 */
		spin_lock(&nfs_wreq_lock);
		req = _nfs_find_request(inode, page);
		if (req) {
			if (!nfs_lock_request_dontget(req)) {
				int error;
				spin_unlock(&nfs_wreq_lock);
				error = nfs_wait_on_request(req);
				nfs_release_request(req);
				if (error < 0)
					return ERR_PTR(error);
				continue;
			}
			spin_unlock(&nfs_wreq_lock);
			if (new)
				nfs_release_request(new);
			break;
		}

		if (new) {
			nfs_lock_request_dontget(new);
			nfs_inode_add_request(inode, new);
			spin_unlock(&nfs_wreq_lock);
			nfs_mark_request_dirty(new);
			return new;
		}
		spin_unlock(&nfs_wreq_lock);

		new = nfs_create_request(file, inode, page, offset, bytes);
		if (IS_ERR(new))
			return new;
		/* If the region is locked, adjust the timeout */
		if (region_locked(inode, new))
			new->wb_timeout = jiffies + NFS_WRITEBACK_LOCKDELAY;
		else
			new->wb_timeout = jiffies + NFS_WRITEBACK_DELAY;
	}

	/* We have a request for our page.
	 * If the creds don't match, or the
	 * page addresses don't match,
	 * tell the caller to wait on the conflicting
	 * request.
	 */
	rqend = req->wb_offset + req->wb_bytes;
	if (req->wb_file != file
	    || req->wb_page != page
	    || !nfs_dirty_request(req)
	    || offset > rqend || end < req->wb_offset) {
		nfs_unlock_request(req);
		return ERR_PTR(-EBUSY);
	}

	/* Okay, the request matches. Update the region */
	if (offset < req->wb_offset) {
		req->wb_offset = offset;
		req->wb_bytes = rqend - req->wb_offset;
	}

	if (end > rqend)
		req->wb_bytes = end - req->wb_offset;

	return req;
}

/*
 * This is the strategy routine for NFS.
 * It is called by nfs_updatepage whenever the user wrote up to the end
 * of a page.
 *
 * We always try to submit a set of requests in parallel so that the
 * server's write code can gather writes. This is mainly for the benefit
 * of NFSv2.
 *
 * We never submit more requests than we think the remote can handle.
 * For UDP sockets, we make sure we don't exceed the congestion window;
 * for TCP, we limit the number of requests to 8.
 *
 * NFS_STRATEGY_PAGES gives the minimum number of requests for NFSv2 that
 * should be sent out in one go. This is for the benefit of NFSv2 servers
 * that perform write gathering.
 *
 * FIXME: Different servers may have different sweet spots.
 * Record the average congestion window in server struct?
 */
#define NFS_STRATEGY_PAGES      8
static void
nfs_strategy(struct inode *inode)
{
	unsigned int	dirty, wpages;

	dirty  = inode->u.nfs_i.ndirty;
	wpages = NFS_SERVER(inode)->wpages;
#ifdef CONFIG_NFS_V3
	if (NFS_PROTO(inode)->version == 2) {
		if (dirty >= NFS_STRATEGY_PAGES * wpages)
			nfs_flush_file(inode, NULL, 0, 0, 0);
	} else if (dirty >= wpages)
		nfs_flush_file(inode, NULL, 0, 0, 0);
#else
	if (dirty >= NFS_STRATEGY_PAGES * wpages)
		nfs_flush_file(inode, NULL, 0, 0, 0);
#endif
}

int
nfs_flush_incompatible(struct file *file, struct page *page)
{
	struct inode	*inode = file->f_dentry->d_inode;
	struct nfs_page	*req;
	int		status = 0;
	/*
	 * Look for a request corresponding to this page. If there
	 * is one, and it belongs to another file, we flush it out
	 * before we try to copy anything into the page. Do this
	 * due to the lack of an ACCESS-type call in NFSv2.
	 * Also do the same if we find a request from an existing
	 * dropped page.
	 */
	req = nfs_find_request(inode,page);
	if (req) {
		if (req->wb_file != file || req->wb_page != page)
			status = nfs_wb_page(inode, page);
		nfs_release_request(req);
	}
	return (status < 0) ? status : 0;
}

/*
 * Update and possibly write a cached page of an NFS file.
 *
 * XXX: Keep an eye on generic_file_read to make sure it doesn't do bad
 * things with a page scheduled for an RPC call (e.g. invalidate it).
 */
int
nfs_updatepage(struct file *file, struct page *page, unsigned int offset, unsigned int count)
{
	struct dentry	*dentry = file->f_dentry;
	struct inode	*inode = dentry->d_inode;
	struct nfs_page	*req;
	loff_t		end;
	int		status = 0;

	dprintk("NFS:      nfs_updatepage(%s/%s %d@%Ld)\n",
		dentry->d_parent->d_name.name, dentry->d_name.name,
		count, (long long)(page_offset(page) +offset));

	/*
	 * If wsize is smaller than page size, update and write
	 * page synchronously.
	 */
	if (NFS_SERVER(inode)->wsize < PAGE_CACHE_SIZE || IS_SYNC(inode))
		return nfs_writepage_sync(file, inode, page, offset, count);

	/*
	 * Try to find an NFS request corresponding to this page
	 * and update it.
	 * If the existing request cannot be updated, we must flush
	 * it out now.
	 */
	do {
		req = nfs_update_request(file, inode, page, offset, count);
		status = (IS_ERR(req)) ? PTR_ERR(req) : 0;
		if (status != -EBUSY)
			break;
		/* Request could not be updated. Flush it out and try again */
		status = nfs_wb_page(inode, page);
	} while (status >= 0);
	if (status < 0)
		goto done;

	status = 0;
	end = ((loff_t)page->index<<PAGE_CACHE_SHIFT) + (loff_t)(offset + count);
	if (inode->i_size < end)
		inode->i_size = end;

	/* If we wrote past the end of the page.
	 * Call the strategy routine so it can send out a bunch
	 * of requests.
	 */
	if (req->wb_offset == 0 && req->wb_bytes == PAGE_CACHE_SIZE) {
		SetPageUptodate(page);
		nfs_unlock_request(req);
		nfs_strategy(inode);
	} else
		nfs_unlock_request(req);
done:
        dprintk("NFS:      nfs_updatepage returns %d (isize %Ld)\n",
                                                status, (long long)inode->i_size);
	if (status < 0)
		ClearPageUptodate(page);
	return status;
}

/*
 * Set up the argument/result storage required for the RPC call.
 */
static void
nfs_write_rpcsetup(struct list_head *head, struct nfs_write_data *data)
{
	struct nfs_page		*req;
	struct iovec		*iov;
	unsigned int		count;

	/* Set up the RPC argument and reply structs
	 * NB: take care not to mess about with data->commit et al. */

	iov = data->args.iov;
	count = 0;
	while (!list_empty(head)) {
		struct nfs_page *req = nfs_list_entry(head->next);
		nfs_list_remove_request(req);
		nfs_list_add_request(req, &data->pages);
		iov->iov_base = kmap(req->wb_page) + req->wb_offset;
		iov->iov_len = req->wb_bytes;
		count += req->wb_bytes;
		iov++;
		data->args.nriov++;
	}
	req = nfs_list_entry(data->pages.next);
	data->inode = req->wb_inode;
	data->cred = req->wb_cred;
	data->args.fh     = NFS_FH(req->wb_inode);
	data->args.offset = page_offset(req->wb_page) + req->wb_offset;
	data->args.count  = count;
	data->res.fattr   = &data->fattr;