aops.c

来自「一个类似windows」· C语言 代码 · 共 1,795 行 · 第 1/4 页

 *
 * If a page doesn't have buffers the page dirty state is definitive. If a page
 * does have buffers, the page dirty state is just a hint, and the buffer dirty
 * state is definitive. (A hint which has rules: dirty buffers against a clean
 * page is illegal. Other combinations are legal and need to be handled. In
 * particular a dirty page containing clean buffers for example.)
 *
 * Return 0 on success and -errno on error.
 *
 * Based on ntfs_read_block() and __block_write_full_page().
 */
static int ntfs_write_block(struct page *page)
{
	VCN vcn;
	LCN lcn;
	sector_t block, dblock, iblock;
	struct inode *vi;
	ntfs_inode *ni;
	ntfs_volume *vol;
	run_list_element *rl;
	struct buffer_head *bh, *head;
	unsigned int blocksize, vcn_ofs;
	int err;
	BOOL need_end_writeback;
	unsigned char blocksize_bits;

	vi = page->mapping->host;
	ni = NTFS_I(vi);
	vol = ni->vol;

	ntfs_debug("Entering for inode %li, attribute type 0x%x, page index "
			"0x%lx.\n", vi->i_ino, ni->type, page->index);

	BUG_ON(!NInoNonResident(ni));
	BUG_ON(NInoMstProtected(ni));

	blocksize_bits = vi->i_blkbits;
	blocksize = 1 << blocksize_bits;

	if (!page_has_buffers(page)) {
		BUG_ON(!PageUptodate(page));
		create_empty_buffers(page, blocksize,
				(1 << BH_Uptodate) | (1 << BH_Dirty));
	}
	bh = head = page_buffers(page);
	if (unlikely(!bh)) {
		ntfs_warning(vol->sb, "Error allocating page buffers. "
				"Redirtying page so we try again later.");
		/*
		 * Put the page back on mapping->dirty_pages, but leave its
		 * buffer's dirty state as-is.
		 */
		// FIXME: Once Andrew's -EAGAIN patch goes in, remove the
		// __set_page_dirty_nobuffers(page) and return -EAGAIN instead
		// of zero.
		__set_page_dirty_nobuffers(page);
		unlock_page(page);
		return 0;
	}

	/* NOTE: Different naming scheme to ntfs_read_block()! */

	/* The first block in the page. */
	block = page->index << (PAGE_CACHE_SHIFT - blocksize_bits);

	/* The first out of bounds block for the data size. */
	dblock = (vi->i_size + blocksize - 1) >> blocksize_bits;

	/* The last (fully or partially) initialized block. */
	iblock = ni->initialized_size >> blocksize_bits;

	/*
	 * Be very careful.  We have no exclusion from __set_page_dirty_buffers
	 * here, and the (potentially unmapped) buffers may become dirty at
	 * any time.  If a buffer becomes dirty here after we've inspected it
	 * then we just miss that fact, and the page stays dirty.
	 *
	 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
	 * handle that here by just cleaning them.
	 */

	/*
	 * Loop through all the buffers in the page, mapping all the dirty
	 * buffers to disk addresses and handling any aliases from the
	 * underlying block device's mapping.
	 */
	rl = NULL;
	err = 0;
	do {
		BOOL is_retry = FALSE;

		if (unlikely(block >= dblock)) {
			/*
			 * Mapped buffers outside i_size will occur, because
			 * this page can be outside i_size when there is a
			 * truncate in progress. The contents of such buffers
			 * were zeroed by ntfs_writepage().
			 *
			 * FIXME: What about the small race window where
			 * ntfs_writepage() has not done any clearing because
			 * the page was within i_size but before we get here,
			 * vmtruncate() modifies i_size?
			 */
			clear_buffer_dirty(bh);
			set_buffer_uptodate(bh);
			continue;
		}

		/* Clean buffers are not written out, so no need to map them. */
		if (!buffer_dirty(bh))
			continue;

		/* Make sure we have enough initialized size. */
		if (unlikely((block >= iblock) &&
				(ni->initialized_size < vi->i_size))) {
			/*
			 * If this page is fully outside initialized size, zero
			 * out all pages between the current initialized size
			 * and the current page. Just use ntfs_readpage() to do
			 * the zeroing transparently.
			 */
			if (block > iblock) {
				// TODO:
				// For each page do:
				// - read_cache_page()
				// Again for each page do:
				// - wait_on_page_locked()
				// - Check (PageUptodate(page) &&
				// 			!PageError(page))
				// Update initialized size in the attribute and
				// in the inode.
				// Again, for each page do:
				// 	__set_page_dirty_buffers();
				// page_cache_release()
				// We don't need to wait on the writes.
				// Update iblock.
			}
			/*
			 * The current page straddles initialized size. Zero
			 * all non-uptodate buffers and set them uptodate (and
			 * dirty?). Note, there aren't any non-uptodate buffers
			 * if the page is uptodate.
			 * FIXME: For an uptodate page, the buffers may need to
			 * be written out because they were not initialized on
			 * disk before.
			 */
			if (!PageUptodate(page)) {
				// TODO:
				// Zero any non-uptodate buffers up to i_size.
				// Set them uptodate and dirty.
			}
			// TODO:
			// Update initialized size in the attribute and in the
			// inode (up to i_size).
			// Update iblock.
			// FIXME: This is inefficient. Try to batch the two
			// size changes to happen in one go.
			ntfs_error(vol->sb, "Writing beyond initialized size "
					"is not supported yet. Sorry.");
			err = -EOPNOTSUPP;
			break;
			// Do NOT set_buffer_new() BUT DO clear buffer range
			// outside write request range.
			// set_buffer_uptodate() on complete buffers as well as
			// set_buffer_dirty().
		}

		/* No need to map buffers that are already mapped. */
		if (buffer_mapped(bh))
			continue;

		/* Unmapped, dirty buffer. Need to map it. */
		bh->b_bdev = vol->sb->s_bdev;

		/* Convert block into corresponding vcn and offset. */
		vcn = (VCN)block << blocksize_bits >> vol->cluster_size_bits;
		vcn_ofs = ((VCN)block << blocksize_bits) &
				vol->cluster_size_mask;
		if (!rl) {
lock_retry_remap:
			down_read(&ni->run_list.lock);
			rl = ni->run_list.rl;
		}
		if (likely(rl != NULL)) {
			/* Seek to element containing target vcn. */
			while (rl->length && rl[1].vcn <= vcn)
				rl++;
			lcn = vcn_to_lcn(rl, vcn);
		} else
			lcn = (LCN)LCN_RL_NOT_MAPPED;
		/* Successful remap. */
		if (lcn >= 0) {
			/* Setup buffer head to point to correct block. */
			bh->b_blocknr = ((lcn << vol->cluster_size_bits) +
					vcn_ofs) >> blocksize_bits;
			set_buffer_mapped(bh);
			continue;
		}
		/* It is a hole, need to instantiate it. */
		if (lcn == LCN_HOLE) {
			// TODO: Instantiate the hole.
			// clear_buffer_new(bh);
			// unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
			ntfs_error(vol->sb, "Writing into sparse regions is "
					"not supported yet. Sorry.");
			err = -EOPNOTSUPP;
			break;
		}
		/* If first try and run list unmapped, map and retry. */
		if (!is_retry && lcn == LCN_RL_NOT_MAPPED) {
			is_retry = TRUE;
			/*
			 * Attempt to map run list, dropping lock for
			 * the duration.
			 */
			up_read(&ni->run_list.lock);
			err = map_run_list(ni, vcn);
			if (likely(!err))
				goto lock_retry_remap;
			rl = NULL;
		}
		/* Failed to map the buffer, even after retrying. */
		bh->b_blocknr = -1UL;
		ntfs_error(vol->sb, "vcn_to_lcn(vcn = 0x%Lx) failed "
				"with error code 0x%Lx%s.",
				(long long)vcn, (long long)-lcn,
				is_retry ? " even after retrying" : "");
		// FIXME: Depending on vol->on_errors, do something.
		if (!err)
			err = -EIO;
		break;
	} while (block++, (bh = bh->b_this_page) != head);

	/* Release the lock if we took it. */
	if (rl)
		up_read(&ni->run_list.lock);

	/* For the error case, need to reset bh to the beginning. */
	bh = head;

	/* Just an optimization, so ->readpage() isn't called later. */
	if (unlikely(!PageUptodate(page))) {
		int uptodate = 1;
		do {
			if (!buffer_uptodate(bh)) {
				uptodate = 0;
				bh = head;
				break;
			}
		} while ((bh = bh->b_this_page) != head);
		if (uptodate)
			SetPageUptodate(page);
	}

	/* Setup all mapped, dirty buffers for async write i/o. */
	do {
		get_bh(bh);
		if (buffer_mapped(bh) && buffer_dirty(bh)) {
			lock_buffer(bh);
			if (test_clear_buffer_dirty(bh)) {
				BUG_ON(!buffer_uptodate(bh));
				mark_buffer_async_write(bh);
			} else
				unlock_buffer(bh);
		} else if (unlikely(err)) {
			/*
			 * For the error case. The buffer may have been set
			 * dirty during attachment to a dirty page.
			 */
			if (err != -ENOMEM)
				clear_buffer_dirty(bh);
		}
	} while ((bh = bh->b_this_page) != head);

	if (unlikely(err)) {
		// TODO: Remove the -EOPNOTSUPP check later on...
		if (unlikely(err == -EOPNOTSUPP))
			err = 0;
		else if (err == -ENOMEM) {
			ntfs_warning(vol->sb, "Error allocating memory. "
					"Redirtying page so we try again "
					"later.");
			/*
			 * Put the page back on mapping->dirty_pages, but
			 * leave its buffer's dirty state as-is.
			 */
			// FIXME: Once Andrew's -EAGAIN patch goes in, remove
			// the __set_page_dirty_nobuffers(page) and set err to
			// -EAGAIN instead of zero.
			__set_page_dirty_nobuffers(page);
			err = 0;
		} else
			SetPageError(page);
	}

	BUG_ON(PageWriteback(page));
	SetPageWriteback(page);		/* Keeps try_to_free_buffers() away. */
	unlock_page(page);

	/*
	 * Submit the prepared buffers for i/o. Note the page is unlocked,
	 * and the async write i/o completion handler can end_page_writeback()
	 * at any time after the *first* submit_bh(). So the buffers can then
	 * disappear...
	 */
	need_end_writeback = TRUE;
	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
			submit_bh(WRITE, bh);
			need_end_writeback = FALSE;
		}
		put_bh(bh);
		bh = next;
	} while (bh != head);

	/* If no i/o was started, need to end_page_writeback(). */
	if (unlikely(need_end_writeback))
		end_page_writeback(page);

	ntfs_debug("Done.");
	return err;
}

/**
 * ntfs_writepage - write a @page to the backing store
 * @page:	page cache page to write out
 *
 * For non-resident attributes, ntfs_writepage() writes the @page by calling
 * the ntfs version of the generic block_write_full_page() function,
 * ntfs_write_block(), which in turn if necessary creates and writes the
 * buffers associated with the page asynchronously.
 *
 * For resident attributes, OTOH, ntfs_writepage() writes the @page by copying
 * the data to the mft record (which at this stage is most likely in memory).
 * Thus, in this case, I/O is synchronous, as even if the mft record is not
 * cached at this point in time, we need to wait for it to be read in before we
 * can do the copy.
 *
 * Note the caller clears the page dirty flag before calling ntfs_writepage().
 *
 * Based on ntfs_readpage() and fs/buffer.c::block_write_full_page().
 *
 * Return 0 on success and -errno on error.
 */
static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
{
	s64 attr_pos;
	struct inode *vi;
	ntfs_inode *ni, *base_ni;
	char *kaddr;
	attr_search_context *ctx;
	MFT_RECORD *m;
	u32 attr_len, bytes;
	int err;

	BUG_ON(!PageLocked(page));

	vi = page->mapping->host;

	/* Is the page fully outside i_size? (truncate in progress) */
	if (unlikely(page->index >= (vi->i_size + PAGE_CACHE_SIZE - 1) >>
			PAGE_CACHE_SHIFT)) {
		unlock_page(page);
		ntfs_debug("Write outside i_size - truncated?");
		return 0;
	}

	ni = NTFS_I(vi);

	if (NInoNonResident(ni)) {
		/*
		 * Only unnamed $DATA attributes can be compressed, encrypted,
		 * and/or sparse.
		 */
		if (ni->type == AT_DATA && !ni->name_len) {
			/* If file is encrypted, deny access, just like NT4. */
			if (NInoEncrypted(ni)) {
				unlock_page(page);
				ntfs_debug("Denying write access to encrypted "
						"file.");
				return -EACCES;
			}
			/* Compressed data streams are handled in compress.c. */
			if (NInoCompressed(ni)) {
				// TODO: Implement and replace this check with
				// return ntfs_write_compressed_block(page);
				unlock_page(page);
				ntfs_error(vi->i_sb, "Writing to compressed "
						"files is not supported yet. "
						"Sorry.");
				return -EOPNOTSUPP;
			}
			// TODO: Implement and remove this check.
			if (NInoSparse(ni)) {
				unlock_page(page);
				ntfs_error(vi->i_sb, "Writing to sparse files "
						"is not supported yet. Sorry.");
				return -EOPNOTSUPP;
			}
		}

		/* We have to zero every time due to mmap-at-end-of-file. */
		if (page->index >= (vi->i_size >> PAGE_CACHE_SHIFT)) {
			/* The page straddles i_size. */
			unsigned int ofs = vi->i_size & ~PAGE_CACHE_MASK;
			kaddr = kmap_atomic(page, KM_USER0);
			memset(kaddr + ofs, 0, PAGE_CACHE_SIZE - ofs);
			flush_dcache_page(page);
			kunmap_atomic(kaddr, KM_USER0);
		}

		// TODO: Implement and remove this check.
		if (NInoMstProtected(ni)) {
			unlock_page(page);
			ntfs_error(vi->i_sb, "Writing to MST protected "
					"attributes is not supported yet. "
					"Sorry.");
			return -EOPNOTSUPP;
		}

		/* Normal data stream. */
		return ntfs_write_block(page);
	}

	/*
	 * Attribute is resident, implying it is not compressed, encrypted, or
	 * mst protected.
	 */
	BUG_ON(page_has_buffers(page));
	BUG_ON(!PageUptodate(page));

	// TODO: Consider using PageWriteback() + unlock_page() in 2.5 once the
	// "VM fiddling has ended". Note, don't forget to replace all the
	// unlock_page() calls further below with end_page_writeback() ones.
	// FIXME: Make sure it is ok to SetPageError() on unlocked page under
	// writeback before doing the change!
#if 0
	SetPageWriteback(page);
	unlock_page(page);
#endif

	if (!NInoAttr(ni))
		base_ni = ni;
	else
		base_ni = ni->ext.base_ntfs_ino;

	/* Map, pin, and lock the mft record. */
	m = map_mft_record(base_ni);