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Keep dirhash tailq locked throughout the entirety of ufsdirhash_destroy() to fix

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a potential race pointed out by pjd. Also use TAILQ_FOREACH_SAFE to iterate over
dirhashes in ufsdirhash_lowmem(), so that we can continue iterating even after a
dirhash is destroyed.

Suggested by:	pjd
Tested by:      pho
Approved by:	dwmalone (mentor)
This commit is contained in:
Sean Nicholas Barkas 2009-06-17 18:55:29 +00:00
parent 8ee45544b2
commit fe1bd0a483
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=194387
1 changed files with 11 additions and 11 deletions
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22
sys/ufs/ufs/ufs_dirhash.c
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@ -1191,16 +1191,14 @@ ufsdirhash_destroy(struct dirhash *dh)
mem = dh->dh_memreq;
dh->dh_memreq = 0;
/* Unlock everything, free the detached memory. */
/* Unlock dirhash and free the detached memory. */
ufsdirhash_release(dh);
DIRHASHLIST_UNLOCK();
for (i = 0; i < narrays; i++)
DIRHASH_BLKFREE(hash[i]);
free(hash, M_DIRHASH);
free(blkfree, M_DIRHASH);
/* Account for the returned memory. */
DIRHASHLIST_LOCK();
ufs_dirhashmem -= mem;
return (mem);
@ -1247,7 +1245,7 @@ ufsdirhash_recycle(int wanted)
static void
ufsdirhash_lowmem()
{
struct dirhash *dh;
struct dirhash *dh, *dh_temp;
int memfreed = 0;
/* XXX: this 10% may need to be adjusted */
int memwanted = ufs_dirhashmem / 10;
@ -1259,8 +1257,7 @@ ufsdirhash_lowmem()
* Delete dirhashes not used for more than ufs_dirhashreclaimage
* seconds. If we can't get a lock on the dirhash, it will be skipped.
*/
for (dh = TAILQ_FIRST(&ufsdirhash_list); dh != NULL; dh =
TAILQ_NEXT(dh, dh_list)) {
TAILQ_FOREACH_SAFE(dh, &ufsdirhash_list, dh_list, dh_temp) {
if (!sx_try_xlock(&dh->dh_lock))
continue;
if (time_second - dh->dh_lastused > ufs_dirhashreclaimage)
@ -1275,11 +1272,14 @@ ufsdirhash_lowmem()
* of the dirhash list. The ones closest to the head should be the
* oldest.
*/
for (dh = TAILQ_FIRST(&ufsdirhash_list); memfreed < memwanted &&
dh !=NULL; dh = TAILQ_NEXT(dh, dh_list)) {
if (!sx_try_xlock(&dh->dh_lock))
continue;
memfreed += ufsdirhash_destroy(dh);
if (memfreed < memwanted) {
TAILQ_FOREACH_SAFE(dh, &ufsdirhash_list, dh_list, dh_temp) {
if (!sx_try_xlock(&dh->dh_lock))
continue;
memfreed += ufsdirhash_destroy(dh);
if (memfreed >= memwanted)
break;
}
}
DIRHASHLIST_UNLOCK();
}