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-rw-r--r--fs/iomap.c116
1 files changed, 116 insertions, 0 deletions
diff --git a/fs/iomap.c b/fs/iomap.c
index b0bc928672af..fe3b9222dd46 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -20,6 +20,7 @@
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
+#include <linux/pagevec.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/backing-dev.h>
@@ -592,6 +593,121 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
}
EXPORT_SYMBOL_GPL(iomap_fiemap);
+/*
+ * Seek for SEEK_DATA / SEEK_HOLE within @page, starting at @lastoff.
+ *
+ * Returns the offset within the file on success, and -ENOENT otherwise.
+ */
+static loff_t
+page_seek_hole_data(struct page *page, loff_t lastoff, int whence)
+{
+ loff_t offset = page_offset(page);
+ struct buffer_head *bh, *head;
+ bool seek_data = whence == SEEK_DATA;
+
+ if (lastoff < offset)
+ lastoff = offset;
+
+ bh = head = page_buffers(page);
+ do {
+ offset += bh->b_size;
+ if (lastoff >= offset)
+ continue;
+
+ /*
+ * Unwritten extents that have data in the page cache covering
+ * them can be identified by the BH_Unwritten state flag.
+ * Pages with multiple buffers might have a mix of holes, data
+ * and unwritten extents - any buffer with valid data in it
+ * should have BH_Uptodate flag set on it.
+ */
+
+ if ((buffer_unwritten(bh) || buffer_uptodate(bh)) == seek_data)
+ return lastoff;
+
+ lastoff = offset;
+ } while ((bh = bh->b_this_page) != head);
+ return -ENOENT;
+}
+
+/*
+ * 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: unwritten and 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];
+
+ /*
+ * At this point, the page may be truncated or
+ * invalidated (changing page->mapping to NULL), or
+ * even swizzled back from swapper_space to tmpfs file
+ * mapping. However, page->index will not change
+ * because we have a reference on the page.
+ *
+ * If current page offset is beyond where we've ended,
+ * we've found a hole.
+ */
+ if (whence == SEEK_HOLE &&
+ lastoff < page_offset(page))
+ goto check_range;
+
+ lock_page(page);
+ if (likely(page->mapping == inode->i_mapping) &&
+ page_has_buffers(page)) {
+ lastoff = page_seek_hole_data(page, lastoff, whence);
+ if (lastoff >= 0) {
+ unlock_page(page);
+ goto check_range;
+ }
+ }
+ unlock_page(page);
+ 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)