/* see btrfs_writepage_start_hook for details on why this is required */
struct btrfs_writepage_fixup {
struct page *page;
+ struct inode *inode;
struct btrfs_work work;
};
struct inode *inode;
u64 page_start;
u64 page_end;
- int ret;
+ int ret = 0;
+ bool free_delalloc_space = true;
fixup = container_of(work, struct btrfs_writepage_fixup, work);
page = fixup->page;
+ inode = fixup->inode;
+ page_start = page_offset(page);
+ page_end = page_offset(page) + PAGE_SIZE - 1;
+
+ /*
+ * This is similar to page_mkwrite, we need to reserve the space before
+ * we take the page lock.
+ */
+ ret = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start,
+ PAGE_SIZE);
again:
lock_page(page);
+
+ /*
+ * Before we queued this fixup, we took a reference on the page.
+ * page->mapping may go NULL, but it shouldn't be moved to a different
+ * address space.
+ */
if (!page->mapping || !PageDirty(page) || !PageChecked(page)) {
- ClearPageChecked(page);
+ /*
+ * Unfortunately this is a little tricky, either
+ *
+ * 1) We got here and our page had already been dealt with and
+ * we reserved our space, thus ret == 0, so we need to just
+ * drop our space reservation and bail. This can happen the
+ * first time we come into the fixup worker, or could happen
+ * while waiting for the ordered extent.
+ * 2) Our page was already dealt with, but we happened to get an
+ * ENOSPC above from the btrfs_delalloc_reserve_space. In
+ * this case we obviously don't have anything to release, but
+ * because the page was already dealt with we don't want to
+ * mark the page with an error, so make sure we're resetting
+ * ret to 0. This is why we have this check _before_ the ret
+ * check, because we do not want to have a surprise ENOSPC
+ * when the page was already properly dealt with.
+ */
+ if (!ret) {
+ btrfs_delalloc_release_extents(BTRFS_I(inode),
+ PAGE_SIZE);
+ btrfs_delalloc_release_space(inode, data_reserved,
+ page_start, PAGE_SIZE,
+ true);
+ }
+ ret = 0;
goto out_page;
}
- inode = page->mapping->host;
- page_start = page_offset(page);
- page_end = page_offset(page) + PAGE_SIZE - 1;
+ /*
+ * We can't mess with the page state unless it is locked, so now that
+ * it is locked bail if we failed to make our space reservation.
+ */
+ if (ret)
+ goto out_page;
lock_extent_bits(&BTRFS_I(inode)->io_tree, page_start, page_end,
&cached_state);
/* already ordered? We're done */
if (PagePrivate2(page))
- goto out;
+ goto out_reserved;
ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), page_start,
PAGE_SIZE);
goto again;
}
- ret = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start,
- PAGE_SIZE);
- if (ret) {
- mapping_set_error(page->mapping, ret);
- end_extent_writepage(page, ret, page_start, page_end);
- ClearPageChecked(page);
- goto out;
- }
-
ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
&cached_state);
- if (ret) {
- mapping_set_error(page->mapping, ret);
- end_extent_writepage(page, ret, page_start, page_end);
- ClearPageChecked(page);
+ if (ret)
goto out_reserved;
- }
- ClearPageChecked(page);
- set_page_dirty(page);
+ /*
+ * Everything went as planned, we're now the owner of a dirty page with
+ * delayed allocation bits set and space reserved for our COW
+ * destination.
+ *
+ * The page was dirty when we started, nothing should have cleaned it.
+ */
+ BUG_ON(!PageDirty(page));
+ free_delalloc_space = false;
out_reserved:
btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
- if (ret)
+ if (free_delalloc_space)
btrfs_delalloc_release_space(inode, data_reserved, page_start,
PAGE_SIZE, true);
-out:
unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end,
&cached_state);
out_page:
+ if (ret) {
+ /*
+ * We hit ENOSPC or other errors. Update the mapping and page
+ * to reflect the errors and clean the page.
+ */
+ mapping_set_error(page->mapping, ret);
+ end_extent_writepage(page, ret, page_start, page_end);
+ clear_page_dirty_for_io(page);
+ SetPageError(page);
+ }
+ ClearPageChecked(page);
unlock_page(page);
put_page(page);
kfree(fixup);
extent_changeset_free(data_reserved);
+ /*
+ * As a precaution, do a delayed iput in case it would be the last iput
+ * that could need flushing space. Recursing back to fixup worker would
+ * deadlock.
+ */
+ btrfs_add_delayed_iput(inode);
}
/*
if (TestClearPagePrivate2(page))
return 0;
+ /*
+ * PageChecked is set below when we create a fixup worker for this page,
+ * don't try to create another one if we're already PageChecked()
+ *
+ * The extent_io writepage code will redirty the page if we send back
+ * EAGAIN.
+ */
if (PageChecked(page))
return -EAGAIN;
if (!fixup)
return -EAGAIN;
+ /*
+ * We are already holding a reference to this inode from
+ * write_cache_pages. We need to hold it because the space reservation
+ * takes place outside of the page lock, and we can't trust
+ * page->mapping outside of the page lock.
+ */
+ ihold(inode);
SetPageChecked(page);
get_page(page);
btrfs_init_work(&fixup->work, btrfs_writepage_fixup_worker, NULL, NULL);
fixup->page = page;
+ fixup->inode = inode;
btrfs_queue_work(fs_info->fixup_workers, &fixup->work);
- return -EBUSY;
+
+ return -EAGAIN;
}
static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
projects / linux.git / blobdiff