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-rw-r--r--fs/xfs/xfs_aops.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 84e3725..91d77ac 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -927,11 +927,26 @@ xfs_vm_writepage(
end_index = offset >> PAGE_CACHE_SHIFT;
last_index = (offset - 1) >> PAGE_CACHE_SHIFT;
if (page->index >= end_index) {
- if ((page->index >= end_index + 1) ||
- !(i_size_read(inode) & (PAGE_CACHE_SIZE - 1))) {
+ unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1);
+
+ /*
+ * Just skip the page if it is fully outside i_size, e.g. due
+ * to a truncate operation that is in progress.
+ */
+ if (page->index >= end_index + 1 || offset_into_page == 0) {
unlock_page(page);
return 0;
}
+
+ /*
+ * The page straddles i_size. It must be zeroed out on each
+ * and every writepage invocation because it may be mmapped.
+ * "A file is mapped in multiples of the page size. For a file
+ * that is not a multiple of the page size, the remaining
+ * memory is zeroed when mapped, and writes to that region are
+ * not written out to the file."
+ */
+ zero_user_segment(page, offset_into_page, PAGE_CACHE_SIZE);
}
end_offset = min_t(unsigned long long,
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