1 files changed, 10 insertions, 0 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index f424e0e5b46b..efca5c1bbb10 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -529,6 +529,7 @@ locking rules:
 open:           yes
 close:          yes
 fault:          yes             can return with page locked
+map_pages:      yes
 page_mkwrite:   yes             can return with page locked
 access:         yes
 
@@ -540,6 +541,15 @@ the page, then ensure it is not already truncated (the page lock will block
 subsequent truncate), and then return with VM_FAULT_LOCKED, and the page
 locked. The VM will unlock the page.
 
+        ->map_pages() is called when VM asks to map easy accessible pages.
+Filesystem should find and map pages associated with offsets from "pgoff"
+till "max_pgoff". ->map_pages() is called with page table locked and must
+not block.  If it's not possible to reach a page without blocking,
+filesystem should skip it. Filesystem should use do_set_pte() to setup
+page table entry. Pointer to entry associated with offset "pgoff" is
+passed in "pte" field in vm_fault structure. Pointers to entries for other
+offsets should be calculated relative to "pte".
+
         ->page_mkwrite() is called when a previously read-only pte is
 about to become writeable. The filesystem again must ensure that there are
 no truncate/invalidate races, and then return with the page locked. If