GFS2: FITRIM ioctl support

The FITRIM ioctl provides an alternative way to send discard requests to
the underlying device. Using the discard mount option results in every
freed block generating a discard request to the block device. This can
be slow, since many block devices can only process discard requests of
larger sizes, and also such operations can be time consuming.

Rather than using the discard mount option, FITRIM allows a sweep of the
filesystem on an occasional basis, and also to optionally avoid sending
down discard requests for smaller regions.

In GFS2 FITRIM will work at resource group granularity. There is a flag
for each resource group which keeps track of which resource groups have
been trimmed. This flag is reset whenever a deallocation occurs in the
resource group, and set whenever a successful FITRIM of that resource
group has taken place. This helps to reduce repeated discard requests
for the same block ranges, again improving performance.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/gfs2_ondisk.h b/include/linux/gfs2_ondisk.h
index b148087f49a6..fa98bdb073b9 100644
--- a/include/linux/gfs2_ondisk.h
+++ b/include/linux/gfs2_ondisk.h
@@ -168,6 +168,7 @@ struct gfs2_rindex {
 #define GFS2_RGF_METAONLY	0x00000002
 #define GFS2_RGF_DATAONLY	0x00000004
 #define GFS2_RGF_NOALLOC	0x00000008
+#define GFS2_RGF_TRIMMED	0x00000010
 
 struct gfs2_rgrp {
 	struct gfs2_meta_header rg_header;