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Commit 92424157 authored by Josef Bacik's avatar Josef Bacik Committed by Al Viro
Browse files

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: default avatarJosef Bacik <josef@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 9ecf639a

Documentation/filesystems/porting

+9 −0
Original line number Diff line number Diff line
@@ -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.