From cb7181ff4b1ca1e4a9dbea8a3982142ce4ed73fd Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Mon, 15 Jul 2019 08:51:00 -0700 Subject: iomap: move the main iteration code into a separate file Move the main iteration code into a separate file so that we can group related functions in a single file instead of having a single enormous source file. Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig --- fs/iomap/apply.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 fs/iomap/apply.c (limited to 'fs/iomap/apply.c') diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c new file mode 100644 index 000000000000..9f956cf23867 --- /dev/null +++ b/fs/iomap/apply.c @@ -0,0 +1,76 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2010 Red Hat, Inc. + * Copyright (c) 2016-2018 Christoph Hellwig. + */ +#include +#include +#include +#include + +#include "../internal.h" + +/* + * Execute a iomap write on a segment of the mapping that spans a + * contiguous range of pages that have identical block mapping state. + * + * This avoids the need to map pages individually, do individual allocations + * for each page and most importantly avoid the need for filesystem specific + * locking per page. Instead, all the operations are amortised over the entire + * range of pages. It is assumed that the filesystems will lock whatever + * resources they require in the iomap_begin call, and release them in the + * iomap_end call. + */ +loff_t +iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags, + const struct iomap_ops *ops, void *data, iomap_actor_t actor) +{ + struct iomap iomap = { 0 }; + loff_t written = 0, ret; + + /* + * Need to map a range from start position for length bytes. This can + * span multiple pages - it is only guaranteed to return a range of a + * single type of pages (e.g. all into a hole, all mapped or all + * unwritten). Failure at this point has nothing to undo. + * + * If allocation is required for this range, reserve the space now so + * that the allocation is guaranteed to succeed later on. Once we copy + * the data into the page cache pages, then we cannot fail otherwise we + * expose transient stale data. If the reserve fails, we can safely + * back out at this point as there is nothing to undo. + */ + ret = ops->iomap_begin(inode, pos, length, flags, &iomap); + if (ret) + return ret; + if (WARN_ON(iomap.offset > pos)) + return -EIO; + if (WARN_ON(iomap.length == 0)) + return -EIO; + + /* + * Cut down the length to the one actually provided by the filesystem, + * as it might not be able to give us the whole size that we requested. + */ + if (iomap.offset + iomap.length < pos + length) + length = iomap.offset + iomap.length - pos; + + /* + * Now that we have guaranteed that the space allocation will succeed. + * we can do the copy-in page by page without having to worry about + * failures exposing transient data. + */ + written = actor(inode, pos, length, data, &iomap); + + /* + * Now the data has been copied, commit the range we've copied. This + * should not fail unless the filesystem has had a fatal error. + */ + if (ops->iomap_end) { + ret = ops->iomap_end(inode, pos, length, + written > 0 ? written : 0, + flags, &iomap); + } + + return written ? written : ret; +} -- cgit v1.2.3