xfs: add online discard support

Now that we have reliably tracking of deleted extents in a
transaction we can easily implement "online" discard support
which calls blkdev_issue_discard once a transaction commits.

The actual discard is a two stage operation as we first have
to mark the busy extent as not available for reuse before we
can start the actual discard.  Note that we don't bother
supporting discard for the non-delaylog mode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index b0aa59e51fd..98b9c91fcdf 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -110,8 +110,10 @@ mempool_t *xfs_ioend_pool;
 #define MNTOPT_GQUOTANOENF "gqnoenforce"/* group quota limit enforcement */
 #define MNTOPT_PQUOTANOENF "pqnoenforce"/* project quota limit enforcement */
 #define MNTOPT_QUOTANOENF  "qnoenforce" /* same as uqnoenforce */
-#define MNTOPT_DELAYLOG   "delaylog"    /* Delayed loging enabled */
-#define MNTOPT_NODELAYLOG "nodelaylog"  /* Delayed loging disabled */
+#define MNTOPT_DELAYLOG    "delaylog"   /* Delayed logging enabled */
+#define MNTOPT_NODELAYLOG  "nodelaylog" /* Delayed logging disabled */
+#define MNTOPT_DISCARD     "discard"    /* Discard unused blocks */
+#define MNTOPT_NODISCARD   "nodiscard"  /* Do not discard unused blocks */
 
 /*
  * Table driven mount option parser.
@@ -355,6 +357,10 @@ xfs_parseargs(
                         mp->m_flags |= XFS_MOUNT_DELAYLOG;
                 } else if (!strcmp(this_char, MNTOPT_NODELAYLOG)) {
                         mp->m_flags &= ~XFS_MOUNT_DELAYLOG;
+                } else if (!strcmp(this_char, MNTOPT_DISCARD)) {
+                        mp->m_flags |= XFS_MOUNT_DISCARD;
+                } else if (!strcmp(this_char, MNTOPT_NODISCARD)) {
+                        mp->m_flags &= ~XFS_MOUNT_DISCARD;
                 } else if (!strcmp(this_char, "ihashsize")) {
                         xfs_warn(mp,
         "ihashsize no longer used, option is deprecated.");
@@ -388,6 +394,13 @@ xfs_parseargs(
                 return EINVAL;
         }
 
+        if ((mp->m_flags & XFS_MOUNT_DISCARD) &&
+            !(mp->m_flags & XFS_MOUNT_DELAYLOG)) {
+                xfs_warn(mp,
+        "the discard option is incompatible with the nodelaylog option");
+                return EINVAL;
+        }
+
 #ifndef CONFIG_XFS_QUOTA
         if (XFS_IS_QUOTA_RUNNING(mp)) {
                 xfs_warn(mp, "quota support not available in this kernel.");
@@ -488,6 +501,7 @@ xfs_showargs(
                 { XFS_MOUNT_FILESTREAMS,        "," MNTOPT_FILESTREAM },
                 { XFS_MOUNT_GRPID,              "," MNTOPT_GRPID },
                 { XFS_MOUNT_DELAYLOG,           "," MNTOPT_DELAYLOG },
+                { XFS_MOUNT_DISCARD,            "," MNTOPT_DISCARD },
                 { 0, NULL }
         };
         static struct proc_xfs_info xfs_info_unset[] = {