git: f17a5900850b - main - ufs: Avoid M_WAITOK allocations when building a dirhash
Mark Johnston
markj at FreeBSD.org
Thu May 20 15:27:44 UTC 2021
The branch main has been updated by markj:
URL: https://cgit.FreeBSD.org/src/commit/?id=f17a5900850b4d449a91cbe9c61dfb62373c3cd1
commit f17a5900850b4d449a91cbe9c61dfb62373c3cd1
Author: Don Morris <dgmorris at earthlink.net>
AuthorDate: 2021-05-20 14:54:38 +0000
Commit: Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-05-20 15:25:45 +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
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D29045
---
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 13094b5a1c97..d1e1bed0bde4 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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