/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- afs_set_page_dirty
- afs_unlink_writeback
- afs_free_writeback
- afs_put_writeback
- afs_fill_page
- afs_prepare_page
- afs_prepare_write
- afs_commit_write
- afs_kill_pages
- afs_write_back_from_locked_page
- afs_writepage
- afs_writepages_region
- afs_writepages
- afs_write_inode
- afs_pages_written_back
- afs_file_write
- afs_writeback_all
- afs_fsync
/* 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"
static int afs_write_back_from_locked_page(struct afs_writeback *wb,
struct page *page);
/*
* 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);
}
/*
* unlink a writeback record because its usage has reached zero
* - must be called with the wb->vnode->writeback_lock held
*/
static void afs_unlink_writeback(struct afs_writeback *wb)
{
struct afs_writeback *front;
struct afs_vnode *vnode = wb->vnode;
list_del_init(&wb->link);
if (!list_empty(&vnode->writebacks)) {
/* if an fsync rises to the front of the queue then wake it
* up */
front = list_entry(vnode->writebacks.next,
struct afs_writeback, link);
if (front->state == AFS_WBACK_SYNCING) {
_debug("wake up sync");
front->state = AFS_WBACK_COMPLETE;
wake_up(&front->waitq);
}
}
}
/*
* free a writeback record
*/
static void afs_free_writeback(struct afs_writeback *wb)
{
_enter("");
key_put(wb->key);
kfree(wb);
}
/*
* dispose of a reference to a writeback record
*/
void afs_put_writeback(struct afs_writeback *wb)
{
struct afs_vnode *vnode = wb->vnode;
_enter("{%d}", wb->usage);
spin_lock(&vnode->writeback_lock);
if (--wb->usage == 0)
afs_unlink_writeback(wb);
else
wb = NULL;
spin_unlock(&vnode->writeback_lock);
if (wb)
afs_free_writeback(wb);
}
/*
* partly or wholly fill a page that's under preparation for writing
*/
static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
unsigned start, unsigned len, struct page *page)
{
int ret;
_enter(",,%u,%u", start, len);
ASSERTCMP(start + len, <=, PAGE_SIZE);
ret = afs_vnode_fetch_data(vnode, key, start, len, page);
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 a page for being written to
*/
static int afs_prepare_page(struct afs_vnode *vnode, struct page *page,
struct key *key, unsigned offset, unsigned to)
{
unsigned eof, tail, start, stop, len;
loff_t i_size, pos;
void *p;
int ret;
_enter("");
if (offset == 0 && to == PAGE_SIZE)
return 0;
p = kmap_atomic(page, KM_USER0);
i_size = i_size_read(&vnode->vfs_inode);
pos = (loff_t) page->index << PAGE_SHIFT;
if (pos >= i_size) {
/* partial write, page beyond EOF */
_debug("beyond");
if (offset > 0)
memset(p, 0, offset);
if (to < PAGE_SIZE)
memset(p + to, 0, PAGE_SIZE - to);
kunmap_atomic(p, KM_USER0);
return 0;
}
if (i_size - pos >= PAGE_SIZE) {
/* partial write, page entirely before EOF */
_debug("before");
tail = eof = PAGE_SIZE;
} else {
/* partial write, page overlaps EOF */
eof = i_size - pos;
_debug("overlap %u", eof);
tail = max(eof, to);
if (tail < PAGE_SIZE)
memset(p + tail, 0, PAGE_SIZE - tail);
if (offset > eof)
memset(p + eof, 0, PAGE_SIZE - eof);
}
kunmap_atomic(p, KM_USER0);
ret = 0;
if (offset > 0 || eof > to) {
/* need to fill one or two bits that aren't going to be written
* (cover both fillers in one read if there are two) */
start = (offset > 0) ? 0 : to;
stop = (eof > to) ? eof : offset;
len = stop - start;
_debug("wr=%u-%u av=0-%u rd=%u@%u",
offset, to, eof, start, len);
ret = afs_fill_page(vnode, key, start, len, page);
}
_leave(" = %d", ret);
return ret;
}
/*
* prepare to perform part of a write to a page
* - the caller holds the page locked, preventing it from being written out or
* modified by anyone else
*/
int afs_prepare_write(struct file *file, struct page *page,
unsigned offset, unsigned to)
{
struct afs_writeback *candidate, *wb;
struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
struct key *key = file->private_data;
pgoff_t index;
int ret;
_enter("{%x:%u},{%lx},%u,%u",
vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
if (!candidate)
return -ENOMEM;
candidate->vnode = vnode;
candidate->first = candidate->last = page->index;
candidate->offset_first = offset;
candidate->to_last = to;
candidate->usage = 1;
candidate->state = AFS_WBACK_PENDING;
init_waitqueue_head(&candidate->waitq);
if (!PageUptodate(page)) {
_debug("not up to date");
ret = afs_prepare_page(vnode, page, key, offset, to);
if (ret < 0) {
kfree(candidate);
_leave(" = %d [prep]", ret);
return ret;
}
}
try_again:
index = page->index;
spin_lock(&vnode->writeback_lock);
/* see if this page is already pending a writeback under a suitable key
* - if so we can just join onto that one */
wb = (struct afs_writeback *) page_private(page);
if (wb) {
if (wb->key == key && wb->state == AFS_WBACK_PENDING)
goto subsume_in_current_wb;
goto flush_conflicting_wb;
}
if (index > 0) {
/* see if we can find an already pending writeback that we can
* append this page to */
list_for_each_entry(wb, &vnode->writebacks, link) {
if (wb->last == index - 1 && wb->key == key &&
wb->state == AFS_WBACK_PENDING)
goto append_to_previous_wb;
}
}
list_add_tail(&candidate->link, &vnode->writebacks);
candidate->key = key_get(key);
spin_unlock(&vnode->writeback_lock);
SetPagePrivate(page);
set_page_private(page, (unsigned long) candidate);
_leave(" = 0 [new]");
return 0;
subsume_in_current_wb:
_debug("subsume");
ASSERTRANGE(wb->first, <=, index, <=, wb->last);
if (index == wb->first && offset < wb->offset_first)
wb->offset_first = offset;
if (index == wb->last && to > wb->to_last)
wb->to_last = to;
spin_unlock(&vnode->writeback_lock);
kfree(candidate);
_leave(" = 0 [sub]");
return 0;
append_to_previous_wb:
_debug("append into %lx-%lx", wb->first, wb->last);
wb->usage++;
wb->last++;
wb->to_last = to;
spin_unlock(&vnode->writeback_lock);
SetPagePrivate(page);
set_page_private(page, (unsigned long) wb);
kfree(candidate);
_leave(" = 0 [app]");
return 0;
/* the page is currently bound to another context, so if it's dirty we
* need to flush it before we can use the new context */
flush_conflicting_wb:
_debug("flush conflict");
if (wb->state == AFS_WBACK_PENDING)
wb->state = AFS_WBACK_CONFLICTING;
spin_unlock(&vnode->writeback_lock);
if (PageDirty(page)) {
ret = afs_write_back_from_locked_page(wb, page);
if (ret < 0) {
afs_put_writeback(candidate);
_leave(" = %d", ret);
return ret;
}
}
/* the page holds a ref on the writeback record */
afs_put_writeback(wb);
set_page_private(page, 0);
ClearPagePrivate(page);
goto try_again;
}
/*
* finalise part of a write to a page
*/
int afs_commit_write(struct file *file, struct page *page,
unsigned offset, unsigned to)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
loff_t i_size, maybe_i_size;
_enter("{%x:%u},{%lx},%u,%u",
vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
maybe_i_size = (loff_t) page->index << PAGE_SHIFT;
maybe_i_size += to;
i_size = i_size_read(&vnode->vfs_inode);
if (maybe_i_size > i_size) {
spin_lock(&vnode->writeback_lock);
i_size = i_size_read(&vnode->vfs_inode);
if (maybe_i_size > i_size)
i_size_write(&vnode->vfs_inode, maybe_i_size);
spin_unlock(&vnode->writeback_lock);
}
SetPageUptodate(page);
set_page_dirty(page);
if (PageDirty(page))
_debug("dirtied");
return 0;
}
/*
* kill all the pages in the given range
*/
static void afs_kill_pages(struct afs_vnode *vnode, bool error,
pgoff_t first, pgoff_t last)
{
struct pagevec pv;
unsigned count, loop;
_enter("{%x:%u},%lx-%lx",
vnode->fid.vid, vnode->fid.vnode, first, last);
pagevec_init(&pv, 0);
do {
_debug("kill %lx-%lx", first, last);
count = last - first + 1;
if (count > PAGEVEC_SIZE)
count = PAGEVEC_SIZE;
pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
first, count, pv.pages);
ASSERTCMP(pv.nr, ==, count);
for (loop = 0; loop < count; loop++) {
ClearPageUptodate(pv.pages[loop]);
if (error)
SetPageError(pv.pages[loop]);
end_page_writeback(pv.pages[loop]);
}
__pagevec_release(&pv);
} while (first < last);
_leave("");
}
/*
* synchronously write back the locked page and any subsequent non-locked dirty
* pages also covered by the same writeback record
*/
static int afs_write_back_from_locked_page(struct afs_writeback *wb,
struct page *primary_page)
{
struct page *pages[8], *page;
unsigned long count;
unsigned n, offset, to;
pgoff_t start, first, last;
int loop, ret;
_enter(",%lx", primary_page->index);
count = 1;
if (!clear_page_dirty_for_io(primary_page))
BUG();
if (test_set_page_writeback(primary_page))
BUG();
/* find all consecutive lockable dirty pages, stopping when we find a
* page that is not immediately lockable, is not dirty or is missing,
* or we reach the end of the range */
start = primary_page->index;
if (start >= wb->last)
goto no_more;
start++;
do {
_debug("more %lx [%lx]", start, count);
n = wb->last - start + 1;
if (n > ARRAY_SIZE(pages))
n = ARRAY_SIZE(pages);
n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping,
start, n, pages);
_debug("fgpc %u", n);
if (n == 0)
goto no_more;
if (pages[0]->index != start) {
do {
put_page(pages[--n]);
} while (n > 0);
goto no_more;
}
for (loop = 0; loop < n; loop++) {
page = pages[loop];
if (page->index > wb->last)
break;
if (!trylock_page(page))
break;
if (!PageDirty(page) ||
page_private(page) != (unsigned long) wb) {
unlock_page(page);
break;
}
if (!clear_page_dirty_for_io(page))
BUG();
if (test_set_page_writeback(page))
BUG();
unlock_page(page);
put_page(page);
}
count += loop;
if (loop < n) {
for (; loop < n; loop++)
put_page(pages[loop]);
goto no_more;
}
start += loop;
} while (start <= wb->last && count < 65536);
no_more:
/* we now have a contiguous set of dirty pages, each with writeback set
* and the dirty mark cleared; the first page is locked and must remain
* so, all the rest are unlocked */
first = primary_page->index;
last = first + count - 1;
offset = (first == wb->first) ? wb->offset_first : 0;
to = (last == wb->last) ? wb->to_last : PAGE_SIZE;
_debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
ret = afs_vnode_store_data(wb, first, last, offset, to);
if (ret < 0) {
switch (ret) {
case -EDQUOT:
case -ENOSPC:
set_bit(AS_ENOSPC,
&wb->vnode->vfs_inode.i_mapping->flags);
break;
case -EROFS:
case -EIO:
case -EREMOTEIO:
case -EFBIG:
case -ENOENT:
case -ENOMEDIUM:
case -ENXIO:
afs_kill_pages(wb->vnode, true, first, last);
set_bit(AS_EIO, &wb->vnode->vfs_inode.i_mapping->flags);
break;
case -EACCES:
case -EPERM:
case -ENOKEY:
case -EKEYEXPIRED:
case -EKEYREJECTED:
case -EKEYREVOKED:
afs_kill_pages(wb->vnode, false, first, last);
break;
default:
break;
}
} else {
ret = count;
}
_leave(" = %d", ret);
return ret;
}
/*
* write a page back to the server
* - the caller locked the page for us
*/
int afs_writepage(struct page *page, struct writeback_control *wbc)
{
struct backing_dev_info *bdi = page->mapping->backing_dev_info;
struct afs_writeback *wb;
int ret;
_enter("{%lx},", page->index);
wb = (struct afs_writeback *) page_private(page);
ASSERT(wb != NULL);
ret = afs_write_back_from_locked_page(wb, page);
unlock_page(page);
if (ret < 0) {
_leave(" = %d", ret);
return 0;
}
wbc->nr_to_write -= ret;
if (wbc->nonblocking && bdi_write_congested(bdi))
wbc->encountered_congestion = 1;
_leave(" = 0");
return 0;
}
/*
* write a region of pages back to the server
*/
static int afs_writepages_region(struct address_space *mapping,
struct writeback_control *wbc,
pgoff_t index, pgoff_t end, pgoff_t *_next)
{
struct backing_dev_info *bdi = mapping->backing_dev_info;
struct afs_writeback *wb;
struct page *page;
int ret, n;
_enter(",,%lx,%lx,", index, end);
do {
n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
1, &page);
if (!n)
break;
_debug("wback %lx", page->index);
if (page->index > end) {
*_next = index;
page_cache_release(page);
_leave(" = 0 [%lx]", *_next);
return 0;
}
/* at this point we hold neither mapping->tree_lock nor lock on
* the page itself: the page may be truncated or invalidated
* (changing page->mapping to NULL), or even swizzled back from
* swapper_space to tmpfs file mapping
*/
lock_page(page);
if (page->mapping != mapping) {
unlock_page(page);
page_cache_release(page);
continue;
}
if (wbc->sync_mode != WB_SYNC_NONE)
wait_on_page_writeback(page);
if (PageWriteback(page) || !PageDirty(page)) {
unlock_page(page);
continue;
}
wb = (struct afs_writeback *) page_private(page);
ASSERT(wb != NULL);
spin_lock(&wb->vnode->writeback_lock);
wb->state = AFS_WBACK_WRITING;
spin_unlock(&wb->vnode->writeback_lock);
ret = afs_write_back_from_locked_page(wb, page);
unlock_page(page);
page_cache_release(page);
if (ret < 0) {
_leave(" = %d", ret);
return ret;
}
wbc->nr_to_write -= ret;
if (wbc->nonblocking && bdi_write_congested(bdi)) {
wbc->encountered_congestion = 1;
break;
}
cond_resched();
} while (index < end && wbc->nr_to_write > 0);
*_next = index;
_leave(" = 0 [%lx]", *_next);
return 0;
}
/*
* write some of the pending data back to the server
*/
int afs_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct backing_dev_info *bdi = mapping->backing_dev_info;
pgoff_t start, end, next;
int ret;
_enter("");
if (wbc->nonblocking && bdi_write_congested(bdi)) {
wbc->encountered_congestion = 1;
_leave(" = 0 [congest]");
return 0;
}
if (wbc->range_cyclic) {
start = mapping->writeback_index;
end = -1;
ret = afs_writepages_region(mapping, wbc, start, end, &next);
if (start > 0 && wbc->nr_to_write > 0 && ret == 0 &&
!(wbc->nonblocking && wbc->encountered_congestion))
ret = afs_writepages_region(mapping, wbc, 0, start,
&next);
mapping->writeback_index = next;
} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
end = (pgoff_t)(LLONG_MAX >> PAGE_CACHE_SHIFT);
ret = afs_writepages_region(mapping, wbc, 0, end, &next);
if (wbc->nr_to_write > 0)
mapping->writeback_index = next;
} else {
start = wbc->range_start >> PAGE_CACHE_SHIFT;
end = wbc->range_end >> PAGE_CACHE_SHIFT;
ret = afs_writepages_region(mapping, wbc, start, end, &next);
}
_leave(" = %d", ret);
return ret;
}
/*
* write an inode back
*/
int afs_write_inode(struct inode *inode, int sync)
{
struct afs_vnode *vnode = AFS_FS_I(inode);
int ret;
_enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
ret = 0;
if (sync) {
ret = filemap_fdatawait(inode->i_mapping);
if (ret < 0)
__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
}
_leave(" = %d", ret);
return ret;
}
/*
* completion of write to server
*/
void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
{
struct afs_writeback *wb = call->wb;
struct pagevec pv;
unsigned count, loop;
pgoff_t first = call->first, last = call->last;
bool free_wb;
_enter("{%x:%u},{%lx-%lx}",
vnode->fid.vid, vnode->fid.vnode, first, last);
ASSERT(wb != NULL);
pagevec_init(&pv, 0);
do {
_debug("done %lx-%lx", first, last);
count = last - first + 1;
if (count > PAGEVEC_SIZE)
count = PAGEVEC_SIZE;
pv.nr = find_get_pages_contig(call->mapping, first, count,
pv.pages);
ASSERTCMP(pv.nr, ==, count);
spin_lock(&vnode->writeback_lock);
for (loop = 0; loop < count; loop++) {
struct page *page = pv.pages[loop];
end_page_writeback(page);
if (page_private(page) == (unsigned long) wb) {
set_page_private(page, 0);
ClearPagePrivate(page);
wb->usage--;
}
}
free_wb = false;
if (wb->usage == 0) {
afs_unlink_writeback(wb);
free_wb = true;
}
spin_unlock(&vnode->writeback_lock);
first += count;
if (free_wb) {
afs_free_writeback(wb);
wb = NULL;
}
__pagevec_release(&pv);
} while (first <= last);
_leave("");
}
/*
* write to an AFS file
*/
ssize_t afs_file_write(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
struct dentry *dentry = iocb->ki_filp->f_path.dentry;
struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
ssize_t result;
size_t count = iov_length(iov, nr_segs);
int ret;
_enter("{%x.%u},{%zu},%lu,",
vnode->fid.vid, vnode->fid.vnode, count, nr_segs);
if (IS_SWAPFILE(&vnode->vfs_inode)) {
printk(KERN_INFO
"AFS: Attempt to write to active swap file!\n");
return -EBUSY;
}
if (!count)
return 0;
result = generic_file_aio_write(iocb, iov, nr_segs, pos);
if (IS_ERR_VALUE(result)) {
_leave(" = %zd", result);
return result;
}
/* return error values for O_SYNC and IS_SYNC() */
if (IS_SYNC(&vnode->vfs_inode) || iocb->ki_filp->f_flags & O_SYNC) {
ret = afs_fsync(iocb->ki_filp, dentry, 1);
if (ret < 0)
result = ret;
}
_leave(" = %zd", result);
return result;
}
/*
* flush the vnode to the fileserver
*/
int afs_writeback_all(struct afs_vnode *vnode)
{
struct address_space *mapping = vnode->vfs_inode.i_mapping;
struct writeback_control wbc = {
.bdi = mapping->backing_dev_info,
.sync_mode = WB_SYNC_ALL,
.nr_to_write = LONG_MAX,
.for_writepages = 1,
.range_cyclic = 1,
};
int ret;
_enter("");
ret = mapping->a_ops->writepages(mapping, &wbc);
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
_leave(" = %d", ret);
return ret;
}
/*
* flush any dirty pages for this process, and check for write errors.
* - the return status from this call provides a reliable indication of
* whether any write errors occurred for this process.
*/
int afs_fsync(struct file *file, struct dentry *dentry, int datasync)
{
struct afs_writeback *wb, *xwb;
struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
int ret;
_enter("{%x:%u},{n=%s},%d",
vnode->fid.vid, vnode->fid.vnode, dentry->d_name.name,
datasync);
/* use a writeback record as a marker in the queue - when this reaches
* the front of the queue, all the outstanding writes are either
* completed or rejected */
wb = kzalloc(sizeof(*wb), GFP_KERNEL);
if (!wb)
return -ENOMEM;
wb->vnode = vnode;
wb->first = 0;
wb->last = -1;
wb->offset_first = 0;
wb->to_last = PAGE_SIZE;
wb->usage = 1;
wb->state = AFS_WBACK_SYNCING;
init_waitqueue_head(&wb->waitq);
spin_lock(&vnode->writeback_lock);
list_for_each_entry(xwb, &vnode->writebacks, link) {
if (xwb->state == AFS_WBACK_PENDING)
xwb->state = AFS_WBACK_CONFLICTING;
}
list_add_tail(&wb->link, &vnode->writebacks);
spin_unlock(&vnode->writeback_lock);
/* push all the outstanding writebacks to the server */
ret = afs_writeback_all(vnode);
if (ret < 0) {
afs_put_writeback(wb);
_leave(" = %d [wb]", ret);
return ret;
}
/* wait for the preceding writes to actually complete */
ret = wait_event_interruptible(wb->waitq,
wb->state == AFS_WBACK_COMPLETE ||
vnode->writebacks.next == &wb->link);
afs_put_writeback(wb);
_leave(" = %d", ret);
return ret;
}