git: 8340548bc84b - stable/12 - ufs: Avoid M_WAITOK allocations when building a dirhash
Mark Johnston
markj at FreeBSD.org
Thu May 27 13:06:44 UTC 2021
The branch stable/12 has been updated by markj:
URL: https://cgit.FreeBSD.org/src/commit/?id=8340548bc84bf1cbfa678febb08e0aa0293fd935
commit 8340548bc84bf1cbfa678febb08e0aa0293fd935
Author: Don Morris <dgmorris at earthlink.net>
AuthorDate: 2021-05-20 14:54:38 +0000
Commit: Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-05-27 13:06:15 +0000
ufs: Avoid M_WAITOK allocations when building a dirhash
At this point the directory's vnode lock is held, so blocking while
waiting for free pages makes the system more susceptible to deadlock in
low memory conditions. This is particularly problematic on NUMA systems
as UMA currently implements a strict first-touch policy.
ufsdirhash_build() already uses M_NOWAIT for other allocations and
already handled failures for the block array allocation, so just convert
to M_NOWAIT.
PR: 253992
Reviewed by: markj, mckusick, vangyzen
(cherry picked from commit f17a5900850b4d449a91cbe9c61dfb62373c3cd1)
---
sys/ufs/ufs/ufs_dirhash.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/sys/ufs/ufs/ufs_dirhash.c b/sys/ufs/ufs/ufs_dirhash.c
index 2f1174d33657..b219d16642c6 100644
--- a/sys/ufs/ufs/ufs_dirhash.c
+++ b/sys/ufs/ufs/ufs_dirhash.c
@@ -108,7 +108,7 @@ static uma_zone_t ufsdirhash_zone;
#define DIRHASHLIST_LOCK() mtx_lock(&ufsdirhash_mtx)
#define DIRHASHLIST_UNLOCK() mtx_unlock(&ufsdirhash_mtx)
-#define DIRHASH_BLKALLOC_WAITOK() uma_zalloc(ufsdirhash_zone, M_WAITOK)
+#define DIRHASH_BLKALLOC() uma_zalloc(ufsdirhash_zone, M_NOWAIT)
#define DIRHASH_BLKFREE(ptr) uma_zfree(ufsdirhash_zone, (ptr))
#define DIRHASH_ASSERT_LOCKED(dh) \
sx_assert(&(dh)->dh_lock, SA_LOCKED)
@@ -425,7 +425,7 @@ ufsdirhash_build(struct inode *ip)
if (dh->dh_blkfree == NULL)
goto fail;
for (i = 0; i < narrays; i++) {
- if ((dh->dh_hash[i] = DIRHASH_BLKALLOC_WAITOK()) == NULL)
+ if ((dh->dh_hash[i] = DIRHASH_BLKALLOC()) == NULL)
goto fail;
for (j = 0; j < DH_NBLKOFF; j++)
dh->dh_hash[i][j] = DIRHASH_EMPTY;
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