ext4: add max_dir_size_kb mount option

[firefly-linux-kernel-4.4.55.git] / Documentation / filesystems / ext4.txt

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 1b7f9acbcbbe450c8d0f3f8a16d592275c61a5dd..104322bf378c314061ae906433e0e81a9abde7e0 100644 (file)
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -375,6 +375,16 @@ dioread_nolock             locking. If the dioread_nolock option is specified
                        Because of the restrictions this options comprises
                        it is off by default (e.g. dioread_lock).
 
+max_dir_size_kb=n      This limits the size of directories so that any
+                       attempt to expand them beyond the specified
+                       limit in kilobytes will cause an ENOSPC error.
+                       This is useful in memory constrained
+                       environments, where a very large directory can
+                       cause severe performance problems or even
+                       provoke the Out Of Memory killer.  (For example,
+                       if there is only 512mb memory available, a 176mb
+                       directory may seriously cramp the system's style.)
+
 i_version              Enable 64-bit inode version support. This option is
                        off by default.