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authorDarrick J. Wong <darrick.wong@oracle.com>2019-07-15 08:51:00 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2019-07-17 07:20:43 -0700
commitcb7181ff4b1ca1e4a9dbea8a3982142ce4ed73fd (patch)
treeda6484b487f636f0eefd781f10b522a5652dd2c8 /fs/iomap
parentafc51aaa22f26cb2894083c4f25097e0950f1609 (diff)
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 <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'fs/iomap')
-rw-r--r--fs/iomap/Makefile1
-rw-r--r--fs/iomap/apply.c76
2 files changed, 77 insertions, 0 deletions
diff --git a/fs/iomap/Makefile b/fs/iomap/Makefile
index 19fd672cd486..2d165388d952 100644
--- a/fs/iomap/Makefile
+++ b/fs/iomap/Makefile
@@ -6,6 +6,7 @@
obj-$(CONFIG_FS_IOMAP) += iomap.o
iomap-y += \
+ apply.o \
buffered-io.o \
direct-io.o \
fiemap.o \
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 <linux/module.h>
+#include <linux/compiler.h>
+#include <linux/fs.h>
+#include <linux/iomap.h>
+
+#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;
+}