diff -u --recursive --new-file --exclude-from=linux-2.6.31-rc6//Documentation/dontdiff --exclude='*.lds' --exclude-from=linux-2.6.31-rc6//.gitignore linux-2.6.31-rc6/block/blk-barrier.c linux/block/blk-barrier.c
--- linux-2.6.31-rc6/block/blk-barrier.c	2009-08-16 09:36:36.431146680 -0400
+++ linux/block/blk-barrier.c	2009-08-16 09:20:15.164578531 -0400
@@ -425,3 +425,4 @@
 					DISCARD_BARRIER, NULL);
 }
 EXPORT_SYMBOL(blkdev_issue_discard);
+EXPORT_SYMBOL(__blkdev_issue_discard);
diff -u --recursive --new-file --exclude-from=linux-2.6.31-rc6//Documentation/dontdiff --exclude='*.lds' --exclude-from=linux-2.6.31-rc6//.gitignore linux-2.6.31-rc6/fs/xfs/linux-2.6/xfs_ioctl.c linux/fs/xfs/linux-2.6/xfs_ioctl.c
--- linux-2.6.31-rc6/fs/xfs/linux-2.6/xfs_ioctl.c	2009-08-16 09:16:39.000433070 -0400
+++ linux/fs/xfs/linux-2.6/xfs_ioctl.c	2009-08-16 09:30:38.973683042 -0400
@@ -1274,6 +1274,31 @@
 	return 0;
 }
 
+int
+xfs_ioc_trim(
+	struct xfs_mount	*mp,
+	__uint32_t		*argp)
+{
+	xfs_agnumber_t		agno;
+	int			error = 0;
+	__uint32_t		minlen;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (get_user(minlen, argp))
+		return -EFAULT;
+
+	down_read(&mp->m_peraglock);
+	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+		error = -xfs_trim_extents(mp, agno, minlen);
+		if (error)
+			break;
+	}
+	up_read(&mp->m_peraglock);
+
+	return error;
+}
+
 /*
  * Note: some of the ioctl's return positive numbers as a
  * byte count indicating success, such as readlink_by_handle.
@@ -1523,6 +1548,9 @@
 		error = xfs_errortag_clearall(mp, 1);
 		return -error;
 
+	case XFS_IOC_TRIM:
+		return xfs_ioc_trim(mp, arg);
+
 	default:
 		return -ENOTTY;
 	}
diff -u --recursive --new-file --exclude-from=linux-2.6.31-rc6//Documentation/dontdiff --exclude='*.lds' --exclude-from=linux-2.6.31-rc6//.gitignore linux-2.6.31-rc6/fs/xfs/linux-2.6/xfs_ioctl32.c linux/fs/xfs/linux-2.6/xfs_ioctl32.c
--- linux-2.6.31-rc6/fs/xfs/linux-2.6/xfs_ioctl32.c	2009-06-09 23:05:27.000000000 -0400
+++ linux/fs/xfs/linux-2.6/xfs_ioctl32.c	2009-08-16 09:31:21.005588977 -0400
@@ -539,6 +539,7 @@
 	void			__user *arg = (void __user *)p;
 	int			ioflags = 0;
 	int			error;
+	extern int xfs_ioc_trim(struct xfs_mount *mp, __uint32_t *argp);
 
 	if (filp->f_mode & FMODE_NOCMTIME)
 		ioflags |= IO_INVIS;
@@ -564,6 +565,8 @@
 	case XFS_IOC_ERROR_INJECTION:
 	case XFS_IOC_ERROR_CLEARALL:
 		return xfs_file_ioctl(filp, cmd, p);
+	case XFS_IOC_TRIM:
+		return xfs_ioc_trim(mp, arg);
 #ifndef BROKEN_X86_ALIGNMENT
 	/* These are handled fine if no alignment issues */
 	case XFS_IOC_ALLOCSP:
diff -u --recursive --new-file --exclude-from=linux-2.6.31-rc6//Documentation/dontdiff --exclude='*.lds' --exclude-from=linux-2.6.31-rc6//.gitignore linux-2.6.31-rc6/fs/xfs/xfs_alloc.h linux/fs/xfs/xfs_alloc.h
--- linux-2.6.31-rc6/fs/xfs/xfs_alloc.h	2009-06-09 23:05:27.000000000 -0400
+++ linux/fs/xfs/xfs_alloc.h	2009-08-16 09:20:15.167913313 -0400
@@ -215,4 +215,7 @@
 	xfs_fsblock_t	bno,	/* starting block number of extent */
 	xfs_extlen_t	len);	/* length of extent */
 
+int xfs_trim_extents(struct xfs_mount *mp, xfs_agnumber_t agno,
+	xfs_extlen_t minlen);
+
 #endif	/* __XFS_ALLOC_H__ */
diff -u --recursive --new-file --exclude-from=linux-2.6.31-rc6//Documentation/dontdiff --exclude='*.lds' --exclude-from=linux-2.6.31-rc6//.gitignore linux-2.6.31-rc6/fs/xfs/xfs_fs.h linux/fs/xfs/xfs_fs.h
--- linux-2.6.31-rc6/fs/xfs/xfs_fs.h	2009-08-16 09:16:39.017099926 -0400
+++ linux/fs/xfs/xfs_fs.h	2009-08-16 09:20:15.171246419 -0400
@@ -475,6 +475,7 @@
 #define XFS_IOC_ATTRMULTI_BY_HANDLE  _IOW ('X', 123, struct xfs_fsop_attrmulti_handlereq)
 #define XFS_IOC_FSGEOMETRY	     _IOR ('X', 124, struct xfs_fsop_geom)
 #define XFS_IOC_GOINGDOWN	     _IOR ('X', 125, __uint32_t)
+#define XFS_IOC_TRIM		     _IOR ('X', 126, __uint32_t)
 /*	XFS_IOC_GETFSUUID ---------- deprecated 140	 */
 
 
--- linux-2.6.31-rc6/fs/xfs/xfs_alloc.c	2009-06-09 23:05:27.000000000 -0400
+++ linux/fs/xfs/xfs_alloc.c	2009-08-16 09:44:51.073580438 -0400
@@ -39,6 +39,9 @@
 #include "xfs_alloc.h"
 #include "xfs_error.h"
 
+int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
+				sector_t nr_sects, gfp_t gfp_mask,
+				unsigned type, struct completion *completion);
 
 #define XFS_ABSDIFF(a,b)	(((a) <= (b)) ? ((b) - (a)) : ((a) - (b)))
 
@@ -2609,6 +2612,97 @@
 	return error;
 }
 
+STATIC int
+xfs_trim_extent(
+	struct xfs_mount	*mp,
+	xfs_agnumber_t		agno,
+	xfs_agblock_t		fbno,
+	xfs_extlen_t		flen)
+{
+	xfs_daddr_t		blkno = XFS_AGB_TO_DADDR(mp, agno, fbno);
+	sector_t		nblks = XFS_FSB_TO_BB(mp, flen);
+	int			error;
+	DECLARE_COMPLETION_ONSTACK(done);
+
+	xfs_fs_cmn_err(CE_NOTE, mp, "discarding sectors [0x%llx-0x%llx]",
+			blkno, (u64)nblks);
+
+	error = -__blkdev_issue_discard(mp->m_ddev_targp->bt_bdev,
+			blkno, nblks, GFP_NOFS, DISCARD_BARRIER, &done);
+	if (error && error != EOPNOTSUPP)
+		xfs_fs_cmn_err(CE_NOTE, mp, "discard failed, error %d", error);
+	return error;
+}
+
+/*
+ * Notify the underlying block device about our free extent map.
+ *
+ * This walks all free extents above a minimum threshold and notifies the
+ * underlying device that these blocks are unused.  That information is
+ * useful for SSDs or thinly provisioned storage in high end arrays or
+ * virtualization scenarios.
+ */
+int
+xfs_trim_extents(
+	struct xfs_mount	*mp,
+	xfs_agnumber_t		agno,
+	xfs_extlen_t		minlen)	/* minimum extent size to bother */
+{
+	struct xfs_btree_cur	*cur;	/* cursor for the by-block btree */
+	struct xfs_buf		*agbp;	/* AGF buffer pointer */
+	xfs_agblock_t		bno;	/* block the for next search */
+	xfs_agblock_t		fbno;	/* start block of found extent */
+	xfs_extlen_t		flen;	/* length of found extent */
+	int			error;
+	int			i;
+
+	error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);
+	if (error)
+		return error;
+
+	bno = 0;
+	for (;;) {
+		cur = xfs_allocbt_init_cursor(mp, NULL, agbp, agno,
+					      XFS_BTNUM_BNO);
+
+		error = xfs_alloc_lookup_ge(cur, bno, minlen, &i);
+		if (error)
+			goto error0;
+		if (!i) {
+			/*
+			 * No more free extents found: done.
+			 */
+			xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+			break;
+		}
+
+		error = xfs_alloc_get_rec(cur, &fbno, &flen, &i);
+		if (error)
+			goto error0;
+		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
+
+		/*
+		 * Pass if the freespace extent isn't long enough to bother.
+		 */
+		if (flen >= minlen) {
+			error = xfs_trim_extent(mp, agno, fbno, flen);
+			if (error) {
+				xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+				break;
+			}
+		}
+
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		bno = fbno + flen;
+	}
+
+out:
+	xfs_buf_relse(agbp);
+	return error;
+error0:
+	xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+	goto out;
+}
 
 /*
  * AG Busy list management