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linux/fs/xfs/xfs_extent_busy.c

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/*
* Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
* Copyright (c) 2010 David Chinner.
* Copyright (c) 2011 Christoph Hellwig.
* 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_fs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_shared.h"
#include "xfs_trans_resv.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_alloc.h"
#include "xfs_extent_busy.h"
#include "xfs_trace.h"
#include "xfs_trans.h"
#include "xfs_log.h"
void
xfs_extent_busy_insert(
struct xfs_trans *tp,
xfs_agnumber_t agno,
xfs_agblock_t bno,
xfs_extlen_t len,
unsigned int flags)
{
struct xfs_extent_busy *new;
struct xfs_extent_busy *busyp;
struct xfs_perag *pag;
struct rb_node **rbp;
struct rb_node *parent = NULL;
new = kmem_zalloc(sizeof(struct xfs_extent_busy), KM_MAYFAIL);
if (!new) {
/*
* No Memory! Since it is now not possible to track the free
* block, make this a synchronous transaction to insure that
* the block is not reused before this transaction commits.
*/
trace_xfs_extent_busy_enomem(tp->t_mountp, agno, bno, len);
xfs_trans_set_sync(tp);
return;
}
new->agno = agno;
new->bno = bno;
new->length = len;
INIT_LIST_HEAD(&new->list);
new->flags = flags;
/* trace before insert to be able to see failed inserts */
trace_xfs_extent_busy(tp->t_mountp, agno, bno, len);
pag = xfs_perag_get(tp->t_mountp, new->agno);
spin_lock(&pag->pagb_lock);
rbp = &pag->pagb_tree.rb_node;
while (*rbp) {
parent = *rbp;
busyp = rb_entry(parent, struct xfs_extent_busy, rb_node);
if (new->bno < busyp->bno) {
rbp = &(*rbp)->rb_left;
ASSERT(new->bno + new->length <= busyp->bno);
} else if (new->bno > busyp->bno) {
rbp = &(*rbp)->rb_right;
ASSERT(bno >= busyp->bno + busyp->length);
} else {
ASSERT(0);
}
}
rb_link_node(&new->rb_node, parent, rbp);
rb_insert_color(&new->rb_node, &pag->pagb_tree);
list_add(&new->list, &tp->t_busy);
spin_unlock(&pag->pagb_lock);
xfs_perag_put(pag);
}
/*
* Search for a busy extent within the range of the extent we are about to
* allocate. You need to be holding the busy extent tree lock when calling
* xfs_extent_busy_search(). This function returns 0 for no overlapping busy
* extent, -1 for an overlapping but not exact busy extent, and 1 for an exact
* match. This is done so that a non-zero return indicates an overlap that
* will require a synchronous transaction, but it can still be
* used to distinguish between a partial or exact match.
*/
int
xfs_extent_busy_search(
struct xfs_mount *mp,
xfs_agnumber_t agno,
xfs_agblock_t bno,
xfs_extlen_t len)
{
struct xfs_perag *pag;
struct rb_node *rbp;
struct xfs_extent_busy *busyp;
int match = 0;
pag = xfs_perag_get(mp, agno);
spin_lock(&pag->pagb_lock);
rbp = pag->pagb_tree.rb_node;
/* find closest start bno overlap */
while (rbp) {
busyp = rb_entry(rbp, struct xfs_extent_busy, rb_node);
if (bno < busyp->bno) {
/* may overlap, but exact start block is lower */
if (bno + len > busyp->bno)
match = -1;
rbp = rbp->rb_left;
} else if (bno > busyp->bno) {
/* may overlap, but exact start block is higher */
if (bno < busyp->bno + busyp->length)
match = -1;
rbp = rbp->rb_right;
} else {
/* bno matches busyp, length determines exact match */
match = (busyp->length == len) ? 1 : -1;
break;
}
}
spin_unlock(&pag->pagb_lock);
xfs_perag_put(pag);
return match;
}
/*
* The found free extent [fbno, fend] overlaps part or all of the given busy
* extent. If the overlap covers the beginning, the end, or all of the busy
* extent, the overlapping portion can be made unbusy and used for the
* allocation. We can't split a busy extent because we can't modify a
* transaction/CIL context busy list, but we can update an entry's block
* number or length.
*
* Returns true if the extent can safely be reused, or false if the search
* needs to be restarted.
*/
STATIC bool
xfs_extent_busy_update_extent(
struct xfs_mount *mp,
struct xfs_perag *pag,
struct xfs_extent_busy *busyp,
xfs_agblock_t fbno,
xfs_extlen_t flen,
bool userdata) __releases(&pag->pagb_lock)
__acquires(&pag->pagb_lock)
{
xfs_agblock_t fend = fbno + flen;
xfs_agblock_t bbno = busyp->bno;
xfs_agblock_t bend = bbno + busyp->length;
/*
* This extent is currently being discarded. Give the thread
* performing the discard a chance to mark the extent unbusy
* and retry.
*/
if (busyp->flags & XFS_EXTENT_BUSY_DISCARDED) {
spin_unlock(&pag->pagb_lock);
delay(1);
spin_lock(&pag->pagb_lock);
return false;
}
/*
* If there is a busy extent overlapping a user allocation, we have
* no choice but to force the log and retry the search.
*
* Fortunately this does not happen during normal operation, but
* only if the filesystem is very low on space and has to dip into
* the AGFL for normal allocations.
*/
if (userdata)
goto out_force_log;
if (bbno < fbno && bend > fend) {
/*
* Case 1:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +---------+
* fbno fend
*/
/*
* We would have to split the busy extent to be able to track
* it correct, which we cannot do because we would have to
* modify the list of busy extents attached to the transaction
* or CIL context, which is immutable.
*
* Force out the log to clear the busy extent and retry the
* search.
*/
goto out_force_log;
} else if (bbno >= fbno && bend <= fend) {
/*
* Case 2:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +-----------------+
* fbno fend
*
* Case 3:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +--------------------------+
* fbno fend
*
* Case 4:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +--------------------------+
* fbno fend
*
* Case 5:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +-----------------------------------+
* fbno fend
*
*/
/*
* The busy extent is fully covered by the extent we are
* allocating, and can simply be removed from the rbtree.
* However we cannot remove it from the immutable list
* tracking busy extents in the transaction or CIL context,
* so set the length to zero to mark it invalid.
*
* We also need to restart the busy extent search from the
* tree root, because erasing the node can rearrange the
* tree topology.
*/
rb_erase(&busyp->rb_node, &pag->pagb_tree);
busyp->length = 0;
return false;
} else if (fend < bend) {
/*
* Case 6:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +---------+
* fbno fend
*
* Case 7:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +------------------+
* fbno fend
*
*/
busyp->bno = fend;
} else if (bbno < fbno) {
/*
* Case 8:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +-------------+
* fbno fend
*
* Case 9:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +----------------------+
* fbno fend
*/
busyp->length = fbno - busyp->bno;
} else {
ASSERT(0);
}
trace_xfs_extent_busy_reuse(mp, pag->pag_agno, fbno, flen);
return true;
out_force_log:
spin_unlock(&pag->pagb_lock);
xfs_log_force(mp, XFS_LOG_SYNC);
trace_xfs_extent_busy_force(mp, pag->pag_agno, fbno, flen);
spin_lock(&pag->pagb_lock);
return false;
}
/*
* For a given extent [fbno, flen], make sure we can reuse it safely.
*/
void
xfs_extent_busy_reuse(
struct xfs_mount *mp,
xfs_agnumber_t agno,
xfs_agblock_t fbno,
xfs_extlen_t flen,
bool userdata)
{
struct xfs_perag *pag;
struct rb_node *rbp;
ASSERT(flen > 0);
pag = xfs_perag_get(mp, agno);
spin_lock(&pag->pagb_lock);
restart:
rbp = pag->pagb_tree.rb_node;
while (rbp) {
struct xfs_extent_busy *busyp =
rb_entry(rbp, struct xfs_extent_busy, rb_node);
xfs_agblock_t bbno = busyp->bno;
xfs_agblock_t bend = bbno + busyp->length;
if (fbno + flen <= bbno) {
rbp = rbp->rb_left;
continue;
} else if (fbno >= bend) {
rbp = rbp->rb_right;
continue;
}
if (!xfs_extent_busy_update_extent(mp, pag, busyp, fbno, flen,
userdata))
goto restart;
}
spin_unlock(&pag->pagb_lock);
xfs_perag_put(pag);
}
/*
* For a given extent [fbno, flen], search the busy extent list to find a
* subset of the extent that is not busy. If *rlen is smaller than
* args->minlen no suitable extent could be found, and the higher level
* code needs to force out the log and retry the allocation.
*/
void
xfs_extent_busy_trim(
struct xfs_alloc_arg *args,
xfs_agblock_t bno,
xfs_extlen_t len,
xfs_agblock_t *rbno,
xfs_extlen_t *rlen)
{
xfs_agblock_t fbno;
xfs_extlen_t flen;
struct rb_node *rbp;
ASSERT(len > 0);
spin_lock(&args->pag->pagb_lock);
restart:
fbno = bno;
flen = len;
rbp = args->pag->pagb_tree.rb_node;
while (rbp && flen >= args->minlen) {
struct xfs_extent_busy *busyp =
rb_entry(rbp, struct xfs_extent_busy, rb_node);
xfs_agblock_t fend = fbno + flen;
xfs_agblock_t bbno = busyp->bno;
xfs_agblock_t bend = bbno + busyp->length;
if (fend <= bbno) {
rbp = rbp->rb_left;
continue;
} else if (fbno >= bend) {
rbp = rbp->rb_right;
continue;
}
/*
* If this is a metadata allocation, try to reuse the busy
* extent instead of trimming the allocation.
*/
if (!args->userdata &&
!(busyp->flags & XFS_EXTENT_BUSY_DISCARDED)) {
if (!xfs_extent_busy_update_extent(args->mp, args->pag,
busyp, fbno, flen,
false))
goto restart;
continue;
}
if (bbno <= fbno) {
/* start overlap */
/*
* Case 1:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +---------+
* fbno fend
*
* Case 2:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +-------------+
* fbno fend
*
* Case 3:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +-------------+
* fbno fend
*
* Case 4:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +-----------------+
* fbno fend
*
* No unbusy region in extent, return failure.
*/
if (fend <= bend)
goto fail;
/*
* Case 5:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +----------------------+
* fbno fend
*
* Case 6:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +--------------------------+
* fbno fend
*
* Needs to be trimmed to:
* +-------+
* fbno fend
*/
fbno = bend;
} else if (bend >= fend) {
/* end overlap */
/*
* Case 7:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +------------------+
* fbno fend
*
* Case 8:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +--------------------------+
* fbno fend
*
* Needs to be trimmed to:
* +-------+
* fbno fend
*/
fend = bbno;
} else {
/* middle overlap */
/*
* Case 9:
* bbno bend
* +BBBBBBBBBBBBBBBBB+
* +-----------------------------------+
* fbno fend
*
* Can be trimmed to:
* +-------+ OR +-------+
* fbno fend fbno fend
*
* Backward allocation leads to significant
* fragmentation of directories, which degrades
* directory performance, therefore we always want to
* choose the option that produces forward allocation
* patterns.
* Preferring the lower bno extent will make the next
* request use "fend" as the start of the next
* allocation; if the segment is no longer busy at
* that point, we'll get a contiguous allocation, but
* even if it is still busy, we will get a forward
* allocation.
* We try to avoid choosing the segment at "bend",
* because that can lead to the next allocation
* taking the segment at "fbno", which would be a
* backward allocation. We only use the segment at
* "fbno" if it is much larger than the current
* requested size, because in that case there's a
* good chance subsequent allocations will be
* contiguous.
*/
if (bbno - fbno >= args->maxlen) {
/* left candidate fits perfect */
fend = bbno;
} else if (fend - bend >= args->maxlen * 4) {
/* right candidate has enough free space */
fbno = bend;
} else if (bbno - fbno >= args->minlen) {
/* left candidate fits minimum requirement */
fend = bbno;
} else {
goto fail;
}
}
flen = fend - fbno;
}
spin_unlock(&args->pag->pagb_lock);
if (fbno != bno || flen != len) {
trace_xfs_extent_busy_trim(args->mp, args->agno, bno, len,
fbno, flen);
}
*rbno = fbno;
*rlen = flen;
return;
fail:
/*
* Return a zero extent length as failure indications. All callers
* re-check if the trimmed extent satisfies the minlen requirement.
*/
spin_unlock(&args->pag->pagb_lock);
trace_xfs_extent_busy_trim(args->mp, args->agno, bno, len, fbno, 0);
*rbno = fbno;
*rlen = 0;
}
STATIC void
xfs_extent_busy_clear_one(
struct xfs_mount *mp,
struct xfs_perag *pag,
struct xfs_extent_busy *busyp)
{
if (busyp->length) {
trace_xfs_extent_busy_clear(mp, busyp->agno, busyp->bno,
busyp->length);
rb_erase(&busyp->rb_node, &pag->pagb_tree);
}
list_del_init(&busyp->list);
kmem_free(busyp);
}
/*
* Remove all extents on the passed in list from the busy extents tree.
* If do_discard is set skip extents that need to be discarded, and mark
* these as undergoing a discard operation instead.
*/
void
xfs_extent_busy_clear(
struct xfs_mount *mp,
struct list_head *list,
bool do_discard)
{
struct xfs_extent_busy *busyp, *n;
struct xfs_perag *pag = NULL;
xfs_agnumber_t agno = NULLAGNUMBER;
list_for_each_entry_safe(busyp, n, list, list) {
if (busyp->agno != agno) {
if (pag) {
spin_unlock(&pag->pagb_lock);
xfs_perag_put(pag);
}
pag = xfs_perag_get(mp, busyp->agno);
spin_lock(&pag->pagb_lock);
agno = busyp->agno;
}
if (do_discard && busyp->length &&
!(busyp->flags & XFS_EXTENT_BUSY_SKIP_DISCARD))
busyp->flags = XFS_EXTENT_BUSY_DISCARDED;
else
xfs_extent_busy_clear_one(mp, pag, busyp);
}
if (pag) {
spin_unlock(&pag->pagb_lock);
xfs_perag_put(pag);
}
}
/*
* Callback for list_sort to sort busy extents by the AG they reside in.
*/
int
xfs_extent_busy_ag_cmp(
void *priv,
struct list_head *a,
struct list_head *b)
{
return container_of(a, struct xfs_extent_busy, list)->agno -
container_of(b, struct xfs_extent_busy, list)->agno;
}
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