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-rw-r--r--mm/filemap.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..9b39a2390b9e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,38 @@ int filemap_flush(struct address_space *mapping)
}
EXPORT_SYMBOL(filemap_flush);
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping: address space within which to check
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+bool filemap_range_has_page(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ pgoff_t index = start_byte >> PAGE_SHIFT;
+ pgoff_t end = end_byte >> PAGE_SHIFT;
+ struct pagevec pvec;
+ bool ret;
+
+ if (end_byte < start_byte)
+ return false;
+
+ if (mapping->nrpages == 0)
+ return false;
+
+ pagevec_init(&pvec, 0);
+ if (!pagevec_lookup(&pvec, mapping, index, 1))
+ return false;
+ ret = (pvec.pages[0]->index <= end);
+ pagevec_release(&pvec);
+ return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
static int __filemap_fdatawait_range(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{