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authorDarrick J. Wong <darrick.wong@oracle.com>2019-07-15 08:50:58 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2019-07-17 07:14:10 -0700
commit56a178981d47075f6fe5e1c4de77036c821d2877 (patch)
treeb2d2decbde2d46f3a6531e5599c29f5a490c6280 /fs/iomap
parent5157fb8f5ae123badeeb5effd0716712066e20d8 (diff)
iomap: move the SEEK_HOLE code into a separate file
Move the SEEK_HOLE/SEEK_DATA 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/Makefile3
-rw-r--r--fs/iomap/seek.c214
2 files changed, 216 insertions, 1 deletions
diff --git a/fs/iomap/Makefile b/fs/iomap/Makefile
index 44cef914020f..5dfe8b5cf330 100644
--- a/fs/iomap/Makefile
+++ b/fs/iomap/Makefile
@@ -6,6 +6,7 @@
obj-$(CONFIG_FS_IOMAP) += iomap.o
iomap-y += \
- fiemap.o
+ fiemap.o \
+ seek.o
iomap-$(CONFIG_SWAP) += swapfile.o
diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
new file mode 100644
index 000000000000..715442eb71aa
--- /dev/null
+++ b/fs/iomap/seek.c
@@ -0,0 +1,214 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 Red Hat, Inc.
+ * Copyright (c) 2018 Christoph Hellwig.
+ */
+#include <linux/module.h>
+#include <linux/compiler.h>
+#include <linux/fs.h>
+#include <linux/iomap.h>
+#include <linux/pagemap.h>
+#include <linux/pagevec.h>
+
+#include "../internal.h"
+
+/*
+ * Seek for SEEK_DATA / SEEK_HOLE within @page, starting at @lastoff.
+ * Returns true if found and updates @lastoff to the offset in file.
+ */
+static bool
+page_seek_hole_data(struct inode *inode, struct page *page, loff_t *lastoff,
+ int whence)
+{
+ const struct address_space_operations *ops = inode->i_mapping->a_ops;
+ unsigned int bsize = i_blocksize(inode), off;
+ bool seek_data = whence == SEEK_DATA;
+ loff_t poff = page_offset(page);
+
+ if (WARN_ON_ONCE(*lastoff >= poff + PAGE_SIZE))
+ return false;
+
+ if (*lastoff < poff) {
+ /*
+ * Last offset smaller than the start of the page means we found
+ * a hole:
+ */
+ if (whence == SEEK_HOLE)
+ return true;
+ *lastoff = poff;
+ }
+
+ /*
+ * Just check the page unless we can and should check block ranges:
+ */
+ if (bsize == PAGE_SIZE || !ops->is_partially_uptodate)
+ return PageUptodate(page) == seek_data;
+
+ lock_page(page);
+ if (unlikely(page->mapping != inode->i_mapping))
+ goto out_unlock_not_found;
+
+ for (off = 0; off < PAGE_SIZE; off += bsize) {
+ if (offset_in_page(*lastoff) >= off + bsize)
+ continue;
+ if (ops->is_partially_uptodate(page, off, bsize) == seek_data) {
+ unlock_page(page);
+ return true;
+ }
+ *lastoff = poff + off + bsize;
+ }
+
+out_unlock_not_found:
+ unlock_page(page);
+ return false;
+}
+
+/*
+ * Seek for SEEK_DATA / SEEK_HOLE in the page cache.
+ *
+ * Within unwritten extents, the page cache determines which parts are holes
+ * and which are data: uptodate buffer heads count as data; everything else
+ * counts as a hole.
+ *
+ * Returns the resulting offset on successs, and -ENOENT otherwise.
+ */
+static loff_t
+page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
+ int whence)
+{
+ pgoff_t index = offset >> PAGE_SHIFT;
+ pgoff_t end = DIV_ROUND_UP(offset + length, PAGE_SIZE);
+ loff_t lastoff = offset;
+ struct pagevec pvec;
+
+ if (length <= 0)
+ return -ENOENT;
+
+ pagevec_init(&pvec);
+
+ do {
+ unsigned nr_pages, i;
+
+ nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping, &index,
+ end - 1);
+ if (nr_pages == 0)
+ break;
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page = pvec.pages[i];
+
+ if (page_seek_hole_data(inode, page, &lastoff, whence))
+ goto check_range;
+ lastoff = page_offset(page) + PAGE_SIZE;
+ }
+ pagevec_release(&pvec);
+ } while (index < end);
+
+ /* When no page at lastoff and we are not done, we found a hole. */
+ if (whence != SEEK_HOLE)
+ goto not_found;
+
+check_range:
+ if (lastoff < offset + length)
+ goto out;
+not_found:
+ lastoff = -ENOENT;
+out:
+ pagevec_release(&pvec);
+ return lastoff;
+}
+
+
+static loff_t
+iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
+ void *data, struct iomap *iomap)
+{
+ switch (iomap->type) {
+ case IOMAP_UNWRITTEN:
+ offset = page_cache_seek_hole_data(inode, offset, length,
+ SEEK_HOLE);
+ if (offset < 0)
+ return length;
+ /* fall through */
+ case IOMAP_HOLE:
+ *(loff_t *)data = offset;
+ return 0;
+ default:
+ return length;
+ }
+}
+
+loff_t
+iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
+{
+ loff_t size = i_size_read(inode);
+ loff_t length = size - offset;
+ loff_t ret;
+
+ /* Nothing to be found before or beyond the end of the file. */
+ if (offset < 0 || offset >= size)
+ return -ENXIO;
+
+ while (length > 0) {
+ ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
+ &offset, iomap_seek_hole_actor);
+ if (ret < 0)
+ return ret;
+ if (ret == 0)
+ break;
+
+ offset += ret;
+ length -= ret;
+ }
+
+ return offset;
+}
+EXPORT_SYMBOL_GPL(iomap_seek_hole);
+
+static loff_t
+iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
+ void *data, struct iomap *iomap)
+{
+ switch (iomap->type) {
+ case IOMAP_HOLE:
+ return length;
+ case IOMAP_UNWRITTEN:
+ offset = page_cache_seek_hole_data(inode, offset, length,
+ SEEK_DATA);
+ if (offset < 0)
+ return length;
+ /*FALLTHRU*/
+ default:
+ *(loff_t *)data = offset;
+ return 0;
+ }
+}
+
+loff_t
+iomap_seek_data(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
+{
+ loff_t size = i_size_read(inode);
+ loff_t length = size - offset;
+ loff_t ret;
+
+ /* Nothing to be found before or beyond the end of the file. */
+ if (offset < 0 || offset >= size)
+ return -ENXIO;
+
+ while (length > 0) {
+ ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
+ &offset, iomap_seek_data_actor);
+ if (ret < 0)
+ return ret;
+ if (ret == 0)
+ break;
+
+ offset += ret;
+ length -= ret;
+ }
+
+ if (length <= 0)
+ return -ENXIO;
+ return offset;
+}
+EXPORT_SYMBOL_GPL(iomap_seek_data);

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