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[XFS] using a spinlock per cpu for superblock counter exclusion results in 

a preēmpt counter overflow at 256p and above. Change the exclusion
mechanism to use atomic bit operations and busy wait loops to emulate the
spin lock exclusion mechanism but without the preempt count issues.

SGI-PV: 950027
SGI-Modid: xfs-linux-melb:xfs-kern:25338a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
This commit is contained in:
David Chinner 2006-03-14 13:29:16 +11:00 committed by Nathan Scott
parent 87cbc49cd4
commit 01e1b69cfc
3 changed files with 28 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/xfs/linux-2.6/xfs_linux.h
View File

@ -75,6 +75,7 @@
#include <linux/sort.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/delay.h>
#include <asm/page.h>
#include <asm/div64.h>

37
fs/xfs/xfs_mount.c
View File

@ -1746,10 +1746,7 @@ xfs_icsb_cpu_notify(
case CPU_UP_PREPARE:
/* Easy Case - initialize the area and locks, and
* then rebalance when online does everything else for us. */
spin_lock_init(&cntp->icsb_lock);
cntp->icsb_icount = 0;
cntp->icsb_ifree = 0;
cntp->icsb_fdblocks = 0;
memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
break;
case CPU_ONLINE:
xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, 0);
@ -1769,9 +1766,7 @@ xfs_icsb_cpu_notify(
mp->m_sb.sb_ifree += cntp->icsb_ifree;
mp->m_sb.sb_fdblocks += cntp->icsb_fdblocks;
cntp->icsb_icount = 0;
cntp->icsb_ifree = 0;
cntp->icsb_fdblocks = 0;
memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, XFS_ICSB_SB_LOCKED);
xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, XFS_ICSB_SB_LOCKED);
@ -1800,7 +1795,7 @@ xfs_icsb_init_counters(
for_each_online_cpu(i) {
cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
spin_lock_init(&cntp->icsb_lock);
memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
}
/*
* start with all counters disabled so that the
@ -1820,6 +1815,22 @@ xfs_icsb_destroy_counters(
}
}
STATIC inline void
xfs_icsb_lock_cntr(
xfs_icsb_cnts_t *icsbp)
{
while (test_and_set_bit(XFS_ICSB_FLAG_LOCK, &icsbp->icsb_flags)) {
ndelay(1000);
}
}
STATIC inline void
xfs_icsb_unlock_cntr(
xfs_icsb_cnts_t *icsbp)
{
clear_bit(XFS_ICSB_FLAG_LOCK, &icsbp->icsb_flags);
}
STATIC inline void
xfs_icsb_lock_all_counters(
@ -1830,7 +1841,7 @@ xfs_icsb_lock_all_counters(
for_each_online_cpu(i) {
cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
spin_lock(&cntp->icsb_lock);
xfs_icsb_lock_cntr(cntp);
}
}
@ -1843,7 +1854,7 @@ xfs_icsb_unlock_all_counters(
for_each_online_cpu(i) {
cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
spin_unlock(&cntp->icsb_lock);
xfs_icsb_unlock_cntr(cntp);
}
}
@ -2070,7 +2081,7 @@ xfs_icsb_modify_counters_int(
again:
cpu = get_cpu();
icsbp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, cpu),
spin_lock(&icsbp->icsb_lock);
xfs_icsb_lock_cntr(icsbp);
if (unlikely(xfs_icsb_counter_disabled(mp, field)))
goto slow_path;
@ -2104,7 +2115,7 @@ again:
BUG();
break;
}
spin_unlock(&icsbp->icsb_lock);
xfs_icsb_unlock_cntr(icsbp);
put_cpu();
if (locked)
XFS_SB_UNLOCK(mp, s);
@ -2120,7 +2131,7 @@ again:
* manner.
*/
slow_path:
spin_unlock(&icsbp->icsb_lock);
xfs_icsb_unlock_cntr(icsbp);
put_cpu();
/* need to hold superblock incase we need

4
fs/xfs/xfs_mount.h
View File

@ -280,9 +280,11 @@ typedef struct xfs_icsb_cnts {
uint64_t icsb_fdblocks;
uint64_t icsb_ifree;
uint64_t icsb_icount;
spinlock_t icsb_lock;
unsigned long icsb_flags;
} xfs_icsb_cnts_t;
#define XFS_ICSB_FLAG_LOCK (1 << 0) /* counter lock bit */
#define XFS_ICSB_SB_LOCKED (1 << 0) /* sb already locked */
#define XFS_ICSB_LAZY_COUNT (1 << 1) /* accuracy not needed */