Viewing: lov_offset.c
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Use is subject to license terms.
*
* Copyright (c) 2012, 2017, Intel Corporation.
*/
/*
* This file is part of Lustre, http://www.lustre.org/
*/
#define DEBUG_SUBSYSTEM S_LOV
#include <obd_class.h>
#include "lov_internal.h"
u64 stripe_width(struct lov_stripe_md *lsm, unsigned int index)
{
struct lov_stripe_md_entry *entry = lsm->lsm_entries[index];
LASSERT(index < lsm->lsm_entry_count);
if (lsme_is_dom(entry))
return entry->lsme_stripe_size;
return (u64)entry->lsme_stripe_size * entry->lsme_stripe_count;
}
/* compute object size given "stripeno" and the ost size */
u64 lov_stripe_size(struct lov_stripe_md *lsm, int index, u64 ost_size,
int stripeno)
{
u64 ssize = lsm->lsm_entries[index]->lsme_stripe_size;
u32 stripe_size;
u64 swidth;
u64 lov_size;
ENTRY;
if (ost_size == 0)
RETURN(0);
swidth = stripe_width(lsm, index);
ost_size = div_u64_rem(ost_size, ssize, &stripe_size);
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);
}
/**
* lov_stripe_pgoff() - Compute file level page idx by stripe level page offset
* @lsm: Striping info
* @index: index to layout component
* @stripe_index: stripe index
* @stripe: Stripe number
*
* Return page offset.
*/
pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, int index,
pgoff_t stripe_index, int stripe)
{
loff_t offset;
offset = lov_stripe_size(lsm, index,
(stripe_index << PAGE_SHIFT) + 1,
stripe);
return offset >> PAGE_SHIFT;
}
/*
* 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, int index, loff_t lov_off,
int stripeno, loff_t *obdoff)
{
unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
u64 stripe_off, this_stripe, swidth;
int ret = 0;
if (lov_off == OBD_OBJECT_EOF) {
*obdoff = OBD_OBJECT_EOF;
return 0;
}
swidth = stripe_width(lsm, index);
lov_off = div64_u64_rem(lov_off, swidth, &stripe_off);
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 |
* ---------------------------------------------------------------------
*/
loff_t lov_size_to_stripe(struct lov_stripe_md *lsm, int index, u64 file_size,
int stripeno)
{
struct lov_stripe_md_entry *lse = lsm->lsm_entries[index];
unsigned long ssize = lse->lsme_stripe_size;
u64 comp_start = lse->lsme_extent.e_start;
u64 stripe_off;
u64 this_stripe;
u64 swidth;
if (file_size == OBD_OBJECT_EOF)
return OBD_OBJECT_EOF;
if (file_size < comp_start)
return 0;
swidth = stripe_width(lsm, index);
file_size = div64_u64_rem(file_size, swidth, &stripe_off);
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.
*
* Closed interval [@obd_start, @obd_end] will be returned if caller needs them.
*/
int lov_stripe_intersects(struct lov_stripe_md *lsm, int index, int stripeno,
struct lu_extent *ext, u64 *obd_start, u64 *obd_end)
{
struct lov_stripe_md_entry *entry = lsm->lsm_entries[index];
u64 start, end;
int start_side, end_side;
u64 loc_start, loc_end;
if (!lu_extent_is_overlapped(ext, &entry->lsme_extent))
return 0;
if (!obd_start)
obd_start = &loc_start;
if (!obd_end)
obd_end = &loc_end;
start = max_t(__u64, ext->e_start, entry->lsme_extent.e_start);
end = min_t(__u64, ext->e_end, entry->lsme_extent.e_end);
if (end != OBD_OBJECT_EOF)
end--;
start_side = lov_stripe_offset(lsm, index, start, stripeno, obd_start);
end_side = lov_stripe_offset(lsm, index, end, stripeno, obd_end);
CDEBUG(D_INODE, "[%lld->%lld] -> [(%d) %lld->%lld (%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, int index, u64 lov_off)
{
unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
u64 stripe_off;
u64 swidth;
swidth = stripe_width(lsm, index);
lov_off = div64_u64_rem(lov_off, swidth, &stripe_off);
/* Puts stripe_off/ssize result into stripe_off */
stripe_off = div_u64(stripe_off, ssize);
return (int) stripe_off;
}
