From 924241575a85249b9d410e38f5b2fcad9035e45c Mon Sep 17 00:00:00 2001 From: Josef Bacik <josef@redhat.com> Date: Wed, 5 Jan 2011 15:00:07 -0500 Subject: [PATCH] fs: add documentation on fallocate hole punching This patch simply adds documentation on how to handle the hole punching mode of fallocate for any filesystem wishing to use it. Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> --- Documentation/filesystems/porting | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index 07a32b42cf9c..266d2059b9b8 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -385,3 +385,12 @@ Documentation/filesystems/vfs.txt for more details. on many or all directory inodes on the way down a path walk (to check for exec permission). These must now be rcu-walk aware (flags & IPERM_RCU). See Documentation/filesystems/vfs.txt for more details. + +-- +[mandatory] + In ->fallocate() you must check the mode option passed in. If your +filesystem does not support hole punching (deallocating space in the middle of a +file) you must return -EOPNOTSUPP if FALLOC_FL_PUNCH_HOLE is set in mode. +Currently you can only have FALLOC_FL_PUNCH_HOLE with FALLOC_FL_KEEP_SIZE set, +so the i_size should not change when hole punching, even when puching the end of +a file off. -- GitLab