xfs: add FITRIM support

Allow manual discards from userspace using the FITRIM ioctl.  This is not
intended to be run during normal workloads, as the freepsace btree walks
can cause large performance degradation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 191 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_discard.c b/fs/xfs/linux-2.6/xfs_discard.c
new file mode 100644
index 000000000000..05201ae719e5
--- /dev/null
+++ b/fs/xfs/linux-2.6/xfs_discard.c
@@ -0,0 +1,191 @@
+/*
+ * Copyright (C) 2010 Red Hat, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include "xfs.h"
+#include "xfs_sb.h"
+#include "xfs_inum.h"
+#include "xfs_log.h"
+#include "xfs_ag.h"
+#include "xfs_mount.h"
+#include "xfs_quota.h"
+#include "xfs_trans.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_btree.h"
+#include "xfs_inode.h"
+#include "xfs_alloc.h"
+#include "xfs_error.h"
+#include "xfs_discard.h"
+#include "xfs_trace.h"
+
+STATIC int
+xfs_trim_extents(
+        struct xfs_mount        *mp,
+        xfs_agnumber_t          agno,
+        xfs_fsblock_t           start,
+        xfs_fsblock_t           len,
+        xfs_fsblock_t           minlen,
+        __uint64_t              *blocks_trimmed)
+{
+        struct block_device     *bdev = mp->m_ddev_targp->bt_bdev;
+        struct xfs_btree_cur    *cur;
+        struct xfs_buf          *agbp;
+        struct xfs_perag        *pag;
+        int                     error;
+        int                     i;
+
+        pag = xfs_perag_get(mp, agno);
+
+        error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);
+        if (error || !agbp)
+                goto out_put_perag;
+
+        cur = xfs_allocbt_init_cursor(mp, NULL, agbp, agno, XFS_BTNUM_CNT);
+
+        /*
+         * Force out the log.  This means any transactions that might have freed
+         * space before we took the AGF buffer lock are now on disk, and the
+         * volatile disk cache is flushed.
+         */
+        xfs_log_force(mp, XFS_LOG_SYNC);
+
+        /*
+         * Look up the longest btree in the AGF and start with it.
+         */
+        error = xfs_alloc_lookup_le(cur, 0,
+                                    XFS_BUF_TO_AGF(agbp)->agf_longest, &i);
+        if (error)
+                goto out_del_cursor;
+
+        /*
+         * Loop until we are done with all extents that are large
+         * enough to be worth discarding.
+         */
+        while (i) {
+                xfs_agblock_t fbno;
+                xfs_extlen_t flen;
+
+                error = xfs_alloc_get_rec(cur, &fbno, &flen, &i);
+                if (error)
+                        goto out_del_cursor;
+                XFS_WANT_CORRUPTED_GOTO(i == 1, out_del_cursor);
+                ASSERT(flen <= XFS_BUF_TO_AGF(agbp)->agf_longest);
+
+                /*
+                 * Too small?  Give up.
+                 */
+                if (flen < minlen) {
+                        trace_xfs_discard_toosmall(mp, agno, fbno, flen);
+                        goto out_del_cursor;
+                }
+
+                /*
+                 * If the extent is entirely outside of the range we are
+                 * supposed to discard skip it.  Do not bother to trim
+                 * down partially overlapping ranges for now.
+                 */
+                if (XFS_AGB_TO_FSB(mp, agno, fbno) + flen < start ||
+                    XFS_AGB_TO_FSB(mp, agno, fbno) >= start + len) {
+                        trace_xfs_discard_exclude(mp, agno, fbno, flen);
+                        goto next_extent;
+                }
+
+                /*
+                 * If any blocks in the range are still busy, skip the
+                 * discard and try again the next time.
+                 */
+                if (xfs_alloc_busy_search(mp, agno, fbno, flen)) {
+                        trace_xfs_discard_busy(mp, agno, fbno, flen);
+                        goto next_extent;
+                }
+
+                trace_xfs_discard_extent(mp, agno, fbno, flen);
+                error = -blkdev_issue_discard(bdev,
+                                XFS_AGB_TO_DADDR(mp, agno, fbno),
+                                XFS_FSB_TO_BB(mp, flen),
+                                GFP_NOFS, 0);
+                if (error)
+                        goto out_del_cursor;
+                *blocks_trimmed += flen;
+
+next_extent:
+                error = xfs_btree_decrement(cur, 0, &i);
+                if (error)
+                        goto out_del_cursor;
+        }
+
+out_del_cursor:
+        xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
+        xfs_buf_relse(agbp);
+out_put_perag:
+        xfs_perag_put(pag);
+        return error;
+}
+
+int
+xfs_ioc_trim(
+        struct xfs_mount                *mp,
+        struct fstrim_range __user      *urange)
+{
+        struct request_queue    *q = mp->m_ddev_targp->bt_bdev->bd_disk->queue;
+        unsigned int            granularity = q->limits.discard_granularity;
+        struct fstrim_range     range;
+        xfs_fsblock_t           start, len, minlen;
+        xfs_agnumber_t          start_agno, end_agno, agno;
+        __uint64_t              blocks_trimmed = 0;
+        int                     error, last_error = 0;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -XFS_ERROR(EPERM);
+        if (copy_from_user(&range, urange, sizeof(range)))
+                return -XFS_ERROR(EFAULT);
+
+        /*
+         * Truncating down the len isn't actually quite correct, but using
+         * XFS_B_TO_FSB would mean we trivially get overflows for values
+         * of ULLONG_MAX or slightly lower.  And ULLONG_MAX is the default
+         * used by the fstrim application.  In the end it really doesn't
+         * matter as trimming blocks is an advisory interface.
+         */
+        start = XFS_B_TO_FSBT(mp, range.start);
+        len = XFS_B_TO_FSBT(mp, range.len);
+        minlen = XFS_B_TO_FSB(mp, max_t(u64, granularity, range.minlen));
+
+        start_agno = XFS_FSB_TO_AGNO(mp, start);
+        if (start_agno >= mp->m_sb.sb_agcount)
+                return -XFS_ERROR(EINVAL);
+
+        end_agno = XFS_FSB_TO_AGNO(mp, start + len);
+        if (end_agno >= mp->m_sb.sb_agcount)
+                end_agno = mp->m_sb.sb_agcount - 1;
+
+        for (agno = start_agno; agno <= end_agno; agno++) {
+                error = -xfs_trim_extents(mp, agno, start, len, minlen,
+                                          &blocks_trimmed);
+                if (error)
+                        last_error = error;
+        }
+
+        if (last_error)
+                return last_error;
+
+        range.len = XFS_FSB_TO_B(mp, blocks_trimmed);
+        if (copy_to_user(urange, &range, sizeof(range)))
+                return -XFS_ERROR(EFAULT);
+        return 0;
+}