--- /dev/null
+/* 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,
+ loff_t pos, struct page *page)
+{
+ loff_t i_size;
+ int ret;
+ int len;
+
+ _enter(",,%llu", (unsigned long long)pos);
+
+ i_size = i_size_read(&vnode->vfs_inode);
+ if (pos + PAGE_CACHE_SIZE > i_size)
+ len = i_size - pos;
+ else
+ len = PAGE_CACHE_SIZE;
+
+ ret = afs_vnode_fetch_data(vnode, key, pos, 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 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_writeback *candidate, *wb;
+ struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+ struct page *page;
+ struct key *key = file->private_data;
+ unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+ unsigned to = from + len;
+ pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+ int ret;
+
+ _enter("{%x:%u},{%lx},%u,%u",
+ vnode->fid.vid, vnode->fid.vnode, index, from, to);
+
+ candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
+ if (!candidate)
+ return -ENOMEM;
+ candidate->vnode = vnode;
+ candidate->first = candidate->last = index;
+ candidate->offset_first = from;
+ candidate->to_last = to;
+ INIT_LIST_HEAD(&candidate->link);
+ candidate->usage = 1;
+ candidate->state = AFS_WBACK_PENDING;
+ init_waitqueue_head(&candidate->waitq);
+
+ page = grab_cache_page_write_begin(mapping, index, flags);
+ if (!page) {
+ kfree(candidate);
+ return -ENOMEM;
+ }
+ *pagep = page;
+ /* page won't leak in error case: it eventually gets cleaned off LRU */
+
+ if (!PageUptodate(page) && len != PAGE_CACHE_SIZE) {
+ ret = afs_fill_page(vnode, key, index << PAGE_CACHE_SHIFT, page);
+ if (ret < 0) {
+ kfree(candidate);
+ _leave(" = %d [prep]", ret);
+ return ret;
+ }
+ SetPageUptodate(page);
+ }
+
+try_again:
+ 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 && from < wb->offset_first)
+ wb->offset_first = from;
+ 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_write_end(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned copied,
+ struct page *page, void *fsdata)
+{
+ struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+ loff_t i_size, maybe_i_size;
+
+ _enter("{%x:%u},{%lx}",
+ vnode->fid.vid, vnode->fid.vnode, page->index);
+
+ maybe_i_size = pos + copied;
+
+ 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);
+ }
+
+ set_page_dirty(page);
+ if (PageDirty(page))
+ _debug("dirtied");
+ unlock_page(page);
+ page_cache_release(page);
+
+ return copied;
+}
+
+/*
+ * 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 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;
+
+ _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 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;
+
+ 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)
+{
+ pgoff_t start, end, next;
+ int ret;
+
+ _enter("");
+
+ 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)
+ 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;
+}
+
+/*
+ * 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, struct iov_iter *from)
+{
+ struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
+ ssize_t result;
+ size_t count = iov_iter_count(from);
+
+ _enter("{%x.%u},{%zu},",
+ vnode->fid.vid, vnode->fid.vnode, count);
+
+ 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_write_iter(iocb, from);
+ if (IS_ERR_VALUE(result)) {
+ _leave(" = %zd", result);
+ return result;
+ }
+
+ _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 = {
+ .sync_mode = WB_SYNC_ALL,
+ .nr_to_write = LONG_MAX,
+ .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, loff_t start, loff_t end, int datasync)
+{
+ struct inode *inode = file_inode(file);
+ struct afs_writeback *wb, *xwb;
+ struct afs_vnode *vnode = AFS_FS_I(inode);
+ int ret;
+
+ _enter("{%x:%u},{n=%pD},%d",
+ vnode->fid.vid, vnode->fid.vnode, file,
+ datasync);
+
+ ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+ if (ret)
+ return ret;
+ mutex_lock(&inode->i_mutex);
+
+ /* 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) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ 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);
+ goto out;
+ }
+
+ /* 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);
+out:
+ mutex_unlock(&inode->i_mutex);
+ return ret;
+}
+
+/*
+ * notification that a previously read-only page is about to become writable
+ * - if it returns an error, the caller will deliver a bus error signal
+ */
+int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
+{
+ struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host);
+
+ _enter("{{%x:%u}},{%lx}",
+ vnode->fid.vid, vnode->fid.vnode, page->index);
+
+ /* wait for the page to be written to the cache before we allow it to
+ * be modified */
+#ifdef CONFIG_AFS_FSCACHE
+ fscache_wait_on_page_write(vnode->cache, page);
+#endif
+
+ _leave(" = 0");
+ return 0;
+}
Code Review / kvmfornfv.git / blobdiff