--- /dev/null
+/*
+ * GPL HEADER START
+ *
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 only,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will 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 version 2 for more details (a copy is included
+ * in the LICENSE file that accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; If not, see
+ * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ * GPL HEADER END
+ */
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Use is subject to license terms.
+ *
+ * Copyright (c) 2011, Intel Corporation.
+ */
+/*
+ * This file is part of Lustre, http://www.lustre.org/
+ * Lustre is a trademark of Sun Microsystems, Inc.
+ */
+
+#define DEBUG_SUBSYSTEM S_LOV
+
+#include "../../include/linux/libcfs/libcfs.h"
+
+#include "../include/obd_class.h"
+
+#include "lov_internal.h"
+
+/* compute object size given "stripeno" and the ost size */
+u64 lov_stripe_size(struct lov_stripe_md *lsm, u64 ost_size,
+ int stripeno)
+{
+ unsigned long ssize = lsm->lsm_stripe_size;
+ unsigned long stripe_size;
+ u64 swidth;
+ u64 lov_size;
+ int magic = lsm->lsm_magic;
+
+ if (ost_size == 0)
+ return 0;
+
+ LASSERT(lsm_op_find(magic) != NULL);
+ lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
+
+ /* lov_do_div64(a, b) returns a % b, and a = a / b */
+ stripe_size = lov_do_div64(ost_size, ssize);
+ if (stripe_size)
+ lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
+ else
+ lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
+
+ return lov_size;
+}
+
+/* we have an offset in file backed by an lov and want to find out where
+ * that offset lands in our given stripe of the file. for the easy
+ * case where the offset is within the stripe, we just have to scale the
+ * offset down to make it relative to the stripe instead of the lov.
+ *
+ * the harder case is what to do when the offset doesn't intersect the
+ * stripe. callers will want start offsets clamped ahead to the start
+ * of the nearest stripe in the file. end offsets similarly clamped to the
+ * nearest ending byte of a stripe in the file:
+ *
+ * all this function does is move offsets to the nearest region of the
+ * stripe, and it does its work "mod" the full length of all the stripes.
+ * consider a file with 3 stripes:
+ *
+ * S E
+ * ---------------------------------------------------------------------
+ * | 0 | 1 | 2 | 0 | 1 | 2 |
+ * ---------------------------------------------------------------------
+ *
+ * to find stripe 1's offsets for S and E, it divides by the full stripe
+ * width and does its math in the context of a single set of stripes:
+ *
+ * S E
+ * -----------------------------------
+ * | 0 | 1 | 2 |
+ * -----------------------------------
+ *
+ * it'll notice that E is outside stripe 1 and clamp it to the end of the
+ * stripe, then multiply it back out by lov_off to give the real offsets in
+ * the stripe:
+ *
+ * S E
+ * ---------------------------------------------------------------------
+ * | 1 | 1 | 1 | 1 | 1 | 1 |
+ * ---------------------------------------------------------------------
+ *
+ * it would have done similarly and pulled S forward to the start of a 1
+ * stripe if, say, S had landed in a 0 stripe.
+ *
+ * this rounding isn't always correct. consider an E lov offset that lands
+ * on a 0 stripe, the "mod stripe width" math will pull it forward to the
+ * start of a 1 stripe, when in fact it wanted to be rounded back to the end
+ * of a previous 1 stripe. this logic is handled by callers and this is why:
+ *
+ * this function returns < 0 when the offset was "before" the stripe and
+ * was moved forward to the start of the stripe in question; 0 when it
+ * falls in the stripe and no shifting was done; > 0 when the offset
+ * was outside the stripe and was pulled back to its final byte. */
+int lov_stripe_offset(struct lov_stripe_md *lsm, u64 lov_off,
+ int stripeno, u64 *obdoff)
+{
+ unsigned long ssize = lsm->lsm_stripe_size;
+ u64 stripe_off, this_stripe, swidth;
+ int magic = lsm->lsm_magic;
+ int ret = 0;
+
+ if (lov_off == OBD_OBJECT_EOF) {
+ *obdoff = OBD_OBJECT_EOF;
+ return 0;
+ }
+
+ LASSERT(lsm_op_find(magic) != NULL);
+
+ lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
+ &swidth);
+
+ /* lov_do_div64(a, b) returns a % b, and a = a / b */
+ stripe_off = lov_do_div64(lov_off, swidth);
+
+ this_stripe = (u64)stripeno * ssize;
+ if (stripe_off < this_stripe) {
+ stripe_off = 0;
+ ret = -1;
+ } else {
+ stripe_off -= this_stripe;
+
+ if (stripe_off >= ssize) {
+ stripe_off = ssize;
+ ret = 1;
+ }
+ }
+
+ *obdoff = lov_off * ssize + stripe_off;
+ return ret;
+}
+
+/* Given a whole-file size and a stripe number, give the file size which
+ * corresponds to the individual object of that stripe.
+ *
+ * This behaves basically in the same was as lov_stripe_offset, except that
+ * file sizes falling before the beginning of a stripe are clamped to the end
+ * of the previous stripe, not the beginning of the next:
+ *
+ * S
+ * ---------------------------------------------------------------------
+ * | 0 | 1 | 2 | 0 | 1 | 2 |
+ * ---------------------------------------------------------------------
+ *
+ * if clamped to stripe 2 becomes:
+ *
+ * S
+ * ---------------------------------------------------------------------
+ * | 0 | 1 | 2 | 0 | 1 | 2 |
+ * ---------------------------------------------------------------------
+ */
+u64 lov_size_to_stripe(struct lov_stripe_md *lsm, u64 file_size,
+ int stripeno)
+{
+ unsigned long ssize = lsm->lsm_stripe_size;
+ u64 stripe_off, this_stripe, swidth;
+ int magic = lsm->lsm_magic;
+
+ if (file_size == OBD_OBJECT_EOF)
+ return OBD_OBJECT_EOF;
+
+ LASSERT(lsm_op_find(magic) != NULL);
+ lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
+ &swidth);
+
+ /* lov_do_div64(a, b) returns a % b, and a = a / b */
+ stripe_off = lov_do_div64(file_size, swidth);
+
+ this_stripe = (u64)stripeno * ssize;
+ if (stripe_off < this_stripe) {
+ /* Move to end of previous stripe, or zero */
+ if (file_size > 0) {
+ file_size--;
+ stripe_off = ssize;
+ } else {
+ stripe_off = 0;
+ }
+ } else {
+ stripe_off -= this_stripe;
+
+ if (stripe_off >= ssize) {
+ /* Clamp to end of this stripe */
+ stripe_off = ssize;
+ }
+ }
+
+ return (file_size * ssize + stripe_off);
+}
+
+/* given an extent in an lov and a stripe, calculate the extent of the stripe
+ * that is contained within the lov extent. this returns true if the given
+ * stripe does intersect with the lov extent. */
+int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
+ u64 start, u64 end, u64 *obd_start, u64 *obd_end)
+{
+ int start_side, end_side;
+
+ start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
+ end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
+
+ CDEBUG(D_INODE, "[%llu->%llu] -> [(%d) %llu->%llu (%d)]\n",
+ start, end, start_side, *obd_start, *obd_end, end_side);
+
+ /* this stripe doesn't intersect the file extent when neither
+ * start or the end intersected the stripe and obd_start and
+ * obd_end got rounded up to the save value. */
+ if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
+ return 0;
+
+ /* as mentioned in the lov_stripe_offset commentary, end
+ * might have been shifted in the wrong direction. This
+ * happens when an end offset is before the stripe when viewed
+ * through the "mod stripe size" math. we detect it being shifted
+ * in the wrong direction and touch it up.
+ * interestingly, this can't underflow since end must be > start
+ * if we passed through the previous check.
+ * (should we assert for that somewhere?) */
+ if (end_side != 0)
+ (*obd_end)--;
+
+ return 1;
+}
+
+/* compute which stripe number "lov_off" will be written into */
+int lov_stripe_number(struct lov_stripe_md *lsm, u64 lov_off)
+{
+ unsigned long ssize = lsm->lsm_stripe_size;
+ u64 stripe_off, swidth;
+ int magic = lsm->lsm_magic;
+
+ LASSERT(lsm_op_find(magic) != NULL);
+ lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
+
+ stripe_off = lov_do_div64(lov_off, swidth);
+
+ /* Puts stripe_off/ssize result into stripe_off */
+ lov_do_div64(stripe_off, ssize);
+
+ return stripe_off;
+}
Code Review / kvmfornfv.git / blobdiff