1 files changed, 10 insertions, 3 deletions

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 18b5ec8cea45..bf4f4b7e11b3 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -282,9 +282,16 @@ stripe=n		Number of filesystem blocks that mballoc will try
                         to use for allocation size and alignment. For RAID5/6
                         systems this should be the number of data
                         disks *  RAID chunk size in file system blocks.
-delalloc        (*)     Deferring block allocation until write-out time.
-nodelalloc              Disable delayed allocation. Blocks are allocation
-                        when data is copied from user to page cache.
+
+delalloc        (*)     Defer block allocation until just before ext4
+                        writes out the block(s) in question.  This
+                        allows ext4 to better allocation decisions
+                        more efficiently.
+nodelalloc              Disable delayed allocation.  Blocks are allocated
+                        when the data is copied from userspace to the
+                        page cache, either via the write(2) system call
+                        or when an mmap'ed page which was previously
+                        unallocated is written for the first time.
 
 max_batch_time=usec     Maximum amount of time ext4 should wait for
                         additional filesystem operations to be batch