/* handling of writes to regular files and writing back to the server
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* 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.
*/
#include <linux/backing-dev.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include "internal.h"
/*
* mark a page as having been made dirty and thus needing writeback
*/
int afs_set_page_dirty(struct page *page)
{
_enter("");
return __set_page_dirty_nobuffers(page);
}
/*
* partly or wholly fill a page that's under preparation for writing
*/
static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
loff_t pos, unsigned int len, struct page *page)
{
struct afs_read *req;
int ret;
_enter(",,%llu", (unsigned long long)pos);
req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
GFP_KERNEL);
if (!req)
return -ENOMEM;
refcount_set(&req->usage, 1);
req->pos = pos;
req->len = len;
req->nr_pages = 1;
req->pages = req->array;
req->pages[0] = page;
get_page(page);
ret = afs_fetch_data(vnode, key, req);
afs_put_read(req);
if (ret < 0) {
if (ret == -ENOENT) {
_debug("got NOENT from server"
" - marking file deleted and stale");
set_bit(AFS_VNODE_DELETED, &vnode->flags);
ret = -ESTALE;
}
}
_leave(" = %d", ret);
return ret;
}
/*
* prepare to perform part of a write to a page
*/
int afs_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
struct page *page;
struct key *key = afs_file_key(file);
unsigned long priv;
unsigned f, from = pos & (PAGE_SIZE - 1);
unsigned t, to = from + len;
pgoff_t index = pos >> PAGE_SHIFT;
int ret;
_enter("{%x:%u},{%lx},%u,%u",
vnode->fid.vid, vnode->fid.vnode, index, from, to);
/* We want to store information about how much of a page is altered in
* page->private.
*/
BUILD_BUG_ON(PAGE_SIZE > 32768 && sizeof(page->private) < 8);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
if (!PageUptodate(page) && len != PAGE_SIZE) {
ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
if (ret < 0) {
unlock_page(page);
put_page(page);
_leave(" = %d [prep]", ret);
return ret;
}
SetPageUptodate(page);
}
/* page won't leak in error case: it eventually gets cleaned off LRU */
*pagep = page;
try_again:
/* See if this page is already partially written in a way that we can
* merge the new write with.
*/
t = f = 0;
if (PagePrivate(page)) {
priv = page_private(page);
f = priv & AFS_PRIV_MAX;
t = priv >> AFS_PRIV_SHIFT;
ASSERTCMP(f, <=, t);
}
if (f != t) {
if (PageWriteback(page)) {
trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
page->index, priv);
goto flush_conflicting_write;
}
/* If the file is being filled locally, allow inter-write
* spaces to be merged into writes. If it's not, only write
* back what the user gives us.
*/
if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
(to < f || from > t))
goto flush_conflicting_write;
if (from < f)
f = from;
if (to > t)
t = to;
} else {
f = from;
t = to;
}
priv = (unsigned long)t << AFS_PRIV_SHIFT;
priv |= f;
trace_afs_page_dirty(vnode, tracepoint_string("begin"),
page->index, priv);
SetPagePrivate(page);
set_page_private(page, priv);
_leave(" = 0");
return 0;
/* The previous write and this write aren't adjacent or overlapping, so
* flush the page out.
*/
flush_conflicting_write:
_debug("flush conflict");
ret = write_one_page(page);
if (ret < 0) {
_leave(" = %d", ret);
return ret;
}
ret = lock_page_killable(page);
if (ret < 0) {