diff options
Diffstat (limited to 'drivers/staging/lustre/lustre/lov/lov_offset.c')
| -rw-r--r-- | drivers/staging/lustre/lustre/lov/lov_offset.c | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/drivers/staging/lustre/lustre/lov/lov_offset.c b/drivers/staging/lustre/lustre/lov/lov_offset.c new file mode 100644 index 000000000000..f62b7e53b665 --- /dev/null +++ b/drivers/staging/lustre/lustre/lov/lov_offset.c @@ -0,0 +1,267 @@ +/* + * 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 <linux/libcfs/libcfs.h> + +#include <obd_class.h> +#include <obd_lov.h> + +#include "lov_internal.h" + +/* compute object size given "stripeno" and the ost size */ +obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size, + int stripeno) +{ + unsigned long ssize = lsm->lsm_stripe_size; + unsigned long stripe_size; + obd_off swidth; + obd_size lov_size; + int magic = lsm->lsm_magic; + ENTRY; + + 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, obd_off lov_off, + int stripeno, obd_off *obdoff) +{ + unsigned long ssize = lsm->lsm_stripe_size; + obd_off 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 = (obd_off)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 | + * --------------------------------------------------------------------- + */ +obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size, + int stripeno) +{ + unsigned long ssize = lsm->lsm_stripe_size; + obd_off 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 = (obd_off)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, + obd_off start, obd_off end, + obd_off *obd_start, obd_off *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, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%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, obd_off lov_off) +{ + unsigned long ssize = lsm->lsm_stripe_size; + obd_off 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; +} |