fs: add hole punching to fallocate

Hole punching has already been implemented by XFS and OCFS2, and has the
potential to be implemented on both BTRFS and EXT4 so we need a generic way to
get to this feature.  The simplest way in my mind is to add FALLOC_FL_PUNCH_HOLE
to fallocate() since it already looks like the normal fallocate() operation.
I've tested this patch with XFS and BTRFS to make sure XFS did what it's
supposed to do and that BTRFS failed like it was supposed to.  Thank you,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/open.c b/fs/open.c
index 4197b9ed023d8d1b1831ddf8f706d2a34a934aa6..5b6ef7e2859e30f6a6d577576c65961e5c001f22 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -223,7 +223,12 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
                return -EINVAL;
 
        /* Return error if mode is not supported */
-       if (mode && !(mode & FALLOC_FL_KEEP_SIZE))
+       if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
+               return -EOPNOTSUPP;
+
+       /* Punch hole must have keep size set */
+       if ((mode & FALLOC_FL_PUNCH_HOLE) &&
+           !(mode & FALLOC_FL_KEEP_SIZE))
                return -EOPNOTSUPP;
 
        if (!(file->f_mode & FMODE_WRITE))

diff --git a/include/linux/falloc.h b/include/linux/falloc.h
index 3c155107d61f3d2f4be840dd2d175651ae1c1aa9..73e0b628e058cc28c8ae4eab030ff88f6f523d58 100644 (file)
--- a/include/linux/falloc.h
+++ b/include/linux/falloc.h
@@ -2,6 +2,7 @@
 #define _FALLOC_H_
 
 #define FALLOC_FL_KEEP_SIZE    0x01 /* default is extend size */
+#define FALLOC_FL_PUNCH_HOLE   0x02 /* de-allocates range */
 
 #ifdef __KERNEL__