linux/fs/xfs/xfs_trans_bmap.c
Darrick J. Wong e1a4e37cc7 xfs: try to avoid blowing out the transaction reservation when bunmaping a shared extent
In a pathological scenario where we are trying to bunmapi a single
extent in which every other block is shared, it's possible that trying
to unmap the entire large extent in a single transaction can generate so
many EFIs that we overflow the transaction reservation.

Therefore, use a heuristic to guess at the number of blocks we can
safely unmap from a reflink file's data fork in an single transaction.
This should prevent problems such as the log head slamming into the tail
and ASSERTs that trigger because we've exceeded the transaction
reservation.

Note that since bunmapi can fail to unmap the entire range, we must also
teach the deferred unmap code to roll into a new transaction whenever we
get low on reservation.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
[hch: random edits, all bugs are my fault]
Signed-off-by: Christoph Hellwig <hch@lst.de>
2017-06-19 08:59:10 -07:00

257 lines
6.4 KiB
C

/*
* Copyright (C) 2016 Oracle. All Rights Reserved.
*
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*
* 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; either version 2
* of the License, or (at your option) any later version.
*
* 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_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_bmap_item.h"
#include "xfs_alloc.h"
#include "xfs_bmap.h"
#include "xfs_inode.h"
/*
* This routine is called to allocate a "bmap update done"
* log item.
*/
struct xfs_bud_log_item *
xfs_trans_get_bud(
struct xfs_trans *tp,
struct xfs_bui_log_item *buip)
{
struct xfs_bud_log_item *budp;
budp = xfs_bud_init(tp->t_mountp, buip);
xfs_trans_add_item(tp, &budp->bud_item);
return budp;
}
/*
* Finish an bmap update and log it to the BUD. Note that the
* transaction is marked dirty regardless of whether the bmap update
* succeeds or fails to support the BUI/BUD lifecycle rules.
*/
int
xfs_trans_log_finish_bmap_update(
struct xfs_trans *tp,
struct xfs_bud_log_item *budp,
struct xfs_defer_ops *dop,
enum xfs_bmap_intent_type type,
struct xfs_inode *ip,
int whichfork,
xfs_fileoff_t startoff,
xfs_fsblock_t startblock,
xfs_filblks_t *blockcount,
xfs_exntst_t state)
{
int error;
error = xfs_bmap_finish_one(tp, dop, ip, type, whichfork, startoff,
startblock, blockcount, state);
/*
* Mark the transaction dirty, even on error. This ensures the
* transaction is aborted, which:
*
* 1.) releases the BUI and frees the BUD
* 2.) shuts down the filesystem
*/
tp->t_flags |= XFS_TRANS_DIRTY;
budp->bud_item.li_desc->lid_flags |= XFS_LID_DIRTY;
return error;
}
/* Sort bmap intents by inode. */
static int
xfs_bmap_update_diff_items(
void *priv,
struct list_head *a,
struct list_head *b)
{
struct xfs_bmap_intent *ba;
struct xfs_bmap_intent *bb;
ba = container_of(a, struct xfs_bmap_intent, bi_list);
bb = container_of(b, struct xfs_bmap_intent, bi_list);
return ba->bi_owner->i_ino - bb->bi_owner->i_ino;
}
/* Get an BUI. */
STATIC void *
xfs_bmap_update_create_intent(
struct xfs_trans *tp,
unsigned int count)
{
struct xfs_bui_log_item *buip;
ASSERT(count == XFS_BUI_MAX_FAST_EXTENTS);
ASSERT(tp != NULL);
buip = xfs_bui_init(tp->t_mountp);
ASSERT(buip != NULL);
/*
* Get a log_item_desc to point at the new item.
*/
xfs_trans_add_item(tp, &buip->bui_item);
return buip;
}
/* Set the map extent flags for this mapping. */
static void
xfs_trans_set_bmap_flags(
struct xfs_map_extent *bmap,
enum xfs_bmap_intent_type type,
int whichfork,
xfs_exntst_t state)
{
bmap->me_flags = 0;
switch (type) {
case XFS_BMAP_MAP:
case XFS_BMAP_UNMAP:
bmap->me_flags = type;
break;
default:
ASSERT(0);
}
if (state == XFS_EXT_UNWRITTEN)
bmap->me_flags |= XFS_BMAP_EXTENT_UNWRITTEN;
if (whichfork == XFS_ATTR_FORK)
bmap->me_flags |= XFS_BMAP_EXTENT_ATTR_FORK;
}
/* Log bmap updates in the intent item. */
STATIC void
xfs_bmap_update_log_item(
struct xfs_trans *tp,
void *intent,
struct list_head *item)
{
struct xfs_bui_log_item *buip = intent;
struct xfs_bmap_intent *bmap;
uint next_extent;
struct xfs_map_extent *map;
bmap = container_of(item, struct xfs_bmap_intent, bi_list);
tp->t_flags |= XFS_TRANS_DIRTY;
buip->bui_item.li_desc->lid_flags |= XFS_LID_DIRTY;
/*
* atomic_inc_return gives us the value after the increment;
* we want to use it as an array index so we need to subtract 1 from
* it.
*/
next_extent = atomic_inc_return(&buip->bui_next_extent) - 1;
ASSERT(next_extent < buip->bui_format.bui_nextents);
map = &buip->bui_format.bui_extents[next_extent];
map->me_owner = bmap->bi_owner->i_ino;
map->me_startblock = bmap->bi_bmap.br_startblock;
map->me_startoff = bmap->bi_bmap.br_startoff;
map->me_len = bmap->bi_bmap.br_blockcount;
xfs_trans_set_bmap_flags(map, bmap->bi_type, bmap->bi_whichfork,
bmap->bi_bmap.br_state);
}
/* Get an BUD so we can process all the deferred rmap updates. */
STATIC void *
xfs_bmap_update_create_done(
struct xfs_trans *tp,
void *intent,
unsigned int count)
{
return xfs_trans_get_bud(tp, intent);
}
/* Process a deferred rmap update. */
STATIC int
xfs_bmap_update_finish_item(
struct xfs_trans *tp,
struct xfs_defer_ops *dop,
struct list_head *item,
void *done_item,
void **state)
{
struct xfs_bmap_intent *bmap;
xfs_filblks_t count;
int error;
bmap = container_of(item, struct xfs_bmap_intent, bi_list);
count = bmap->bi_bmap.br_blockcount;
error = xfs_trans_log_finish_bmap_update(tp, done_item, dop,
bmap->bi_type,
bmap->bi_owner, bmap->bi_whichfork,
bmap->bi_bmap.br_startoff,
bmap->bi_bmap.br_startblock,
&count,
bmap->bi_bmap.br_state);
if (!error && count > 0) {
ASSERT(bmap->bi_type == XFS_BMAP_UNMAP);
bmap->bi_bmap.br_blockcount = count;
return -EAGAIN;
}
kmem_free(bmap);
return error;
}
/* Abort all pending BUIs. */
STATIC void
xfs_bmap_update_abort_intent(
void *intent)
{
xfs_bui_release(intent);
}
/* Cancel a deferred rmap update. */
STATIC void
xfs_bmap_update_cancel_item(
struct list_head *item)
{
struct xfs_bmap_intent *bmap;
bmap = container_of(item, struct xfs_bmap_intent, bi_list);
kmem_free(bmap);
}
static const struct xfs_defer_op_type xfs_bmap_update_defer_type = {
.type = XFS_DEFER_OPS_TYPE_BMAP,
.max_items = XFS_BUI_MAX_FAST_EXTENTS,
.diff_items = xfs_bmap_update_diff_items,
.create_intent = xfs_bmap_update_create_intent,
.abort_intent = xfs_bmap_update_abort_intent,
.log_item = xfs_bmap_update_log_item,
.create_done = xfs_bmap_update_create_done,
.finish_item = xfs_bmap_update_finish_item,
.cancel_item = xfs_bmap_update_cancel_item,
};
/* Register the deferred op type. */
void
xfs_bmap_update_init_defer_op(void)
{
xfs_defer_init_op_type(&xfs_bmap_update_defer_type);
}