From 9cdabfa62ac2aabc8966d56402646e71c3748fc9 Mon Sep 17 00:00:00 2001 From: Michael Kerrisk Date: Fri, 27 Feb 2015 08:59:18 +0100 Subject: [PATCH] mount.2: Enhancements to MS_LAZYTIME description Cowritten-by: Theodore Ts'o Signed-off-by: Michael Kerrisk --- man2/mount.2 | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/man2/mount.2 b/man2/mount.2 index a0b9550d6..d864a573b 100644 --- a/man2/mount.2 +++ b/man2/mount.2 @@ -173,9 +173,25 @@ an undeleted inode is evicted from memory; or more than 24 hours have passed since the inode was written to disk. .RE .IP -This mount option significantly reduces writes to the inode table -for some workloads -(e.g., when performing frequent random writes to preallocated files). +This mount significantly reduces writes +needed to update the inode's timestamps, especially mtime and atime. +However, in the event of a system crash, the atime and mtime fields +on disk might be out of date by up to 24 hours. + +Examples of workloads where this option could be of significant benefit +include frequent random writes to preallocated files, +as well as cases where the +.B MS_STRICTATIME +mount option is also enabled. +(The advantage of +.I "(MS_STRICTATIME\ | MS_LAZYTIME)" +is that +.BR stat (2) +will return the correctly updated atime, but the atime updates +will be flushed to disk only when (1) the inode needs to be +updated for filesystem / data consistency reasons or (2) the +inode is pushed out of memory, or (3) the filesystem is +unmounted.) .TP .B MS_MANDLOCK Permit mandatory locking on files in this filesystem.