Date: Fri, 09 Jan 2026 14:16:17 +0000 From: Brooks Davis <brooks@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: fb0bdbea2ed4 - main - cache: avoid hardcoded zone alignment Message-ID: <69610db1.b641.135d9243@gitrepo.freebsd.org>
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The branch main has been updated by brooks: URL: https://cgit.FreeBSD.org/src/commit/?id=fb0bdbea2ed4f63ef07061313f8cef89a3d73579 commit fb0bdbea2ed4f63ef07061313f8cef89a3d73579 Author: Brooks Davis <brooks@FreeBSD.org> AuthorDate: 2026-01-09 14:15:22 +0000 Commit: Brooks Davis <brooks@FreeBSD.org> CommitDate: 2026-01-09 14:15:22 +0000 cache: avoid hardcoded zone alignment Previously, this was underaligned on CHERI system where pointers are larger than time_t. Use the alignment of struct namecache_ts which picks up time_t via strut timespec and pointers via struct namecache. This arguably overaligns cache_zone_small and cache_zone_large on i386 kernels, but I suspect the actual microarchitectures most i386 binaries are run on do better with 64-bit alignment. Reviewed by: olce, markj Effort: CHERI upstreaming Sponsored by: Innovate UK Fixes: cf8ac0de8150 ("cache: reduce zone alignment to 8 bytes") Differential Revision: https://reviews.freebsd.org/D54376 --- sys/kern/vfs_cache.c | 46 ++++++++++++++++++++++++---------------------- 1 file changed, 24 insertions(+), 22 deletions(-) diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index 557e451f9a45..c5abc1c8b9b7 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -384,14 +384,10 @@ struct namecache { }; /* - * struct namecache_ts repeats struct namecache layout up to the - * nc_nlen member. * struct namecache_ts is used in place of struct namecache when time(s) need * to be stored. The nc_dotdottime field is used when a cache entry is mapping * both a non-dotdot directory name plus dotdot for the directory's * parent. - * - * See below for alignment requirement. */ struct namecache_ts { struct timespec nc_time; /* timespec provided by fs */ @@ -404,12 +400,10 @@ struct namecache_ts { TAILQ_HEAD(cache_freebatch, namecache); /* - * At least mips n32 performs 64-bit accesses to timespec as found - * in namecache_ts and requires them to be aligned. Since others - * may be in the same spot suffer a little bit and enforce the - * alignment for everyone. Note this is a nop for 64-bit platforms. + * Ensure all zones are sufficently aligned to hold both + * struct namecache and struct namecache_ts. */ -#define CACHE_ZONE_ALIGNMENT UMA_ALIGNOF(time_t) +#define CACHE_ZONE_ALIGN_MASK UMA_ALIGNOF(struct namecache_ts) /* * TODO: the initial value of CACHE_PATH_CUTOFF was inherited from the @@ -432,15 +426,23 @@ TAILQ_HEAD(cache_freebatch, namecache); #define CACHE_LARGE_PAD 2 #endif -#define CACHE_ZONE_SMALL_SIZE (offsetof(struct namecache, nc_name) + CACHE_PATH_CUTOFF + 1) -#define CACHE_ZONE_SMALL_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_SMALL_SIZE) -#define CACHE_ZONE_LARGE_SIZE (offsetof(struct namecache, nc_name) + NAME_MAX + 1 + CACHE_LARGE_PAD) -#define CACHE_ZONE_LARGE_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_LARGE_SIZE) - -_Static_assert((CACHE_ZONE_SMALL_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size"); -_Static_assert((CACHE_ZONE_SMALL_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size"); -_Static_assert((CACHE_ZONE_LARGE_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size"); -_Static_assert((CACHE_ZONE_LARGE_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size"); +#define CACHE_ZONE_SMALL_SIZE \ + (offsetof(struct namecache, nc_name) + CACHE_PATH_CUTOFF + 1) +#define CACHE_ZONE_SMALL_TS_SIZE \ + (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_SMALL_SIZE) +#define CACHE_ZONE_LARGE_SIZE \ + (offsetof(struct namecache, nc_name) + NAME_MAX + 1 + CACHE_LARGE_PAD) +#define CACHE_ZONE_LARGE_TS_SIZE \ + (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_LARGE_SIZE) + +_Static_assert((CACHE_ZONE_SMALL_SIZE % (CACHE_ZONE_ALIGN_MASK + 1)) == 0, + "bad zone size"); +_Static_assert((CACHE_ZONE_SMALL_TS_SIZE % (CACHE_ZONE_ALIGN_MASK + 1)) == 0, + "bad zone size"); +_Static_assert((CACHE_ZONE_LARGE_SIZE % (CACHE_ZONE_ALIGN_MASK + 1)) == 0, + "bad zone size"); +_Static_assert((CACHE_ZONE_LARGE_TS_SIZE % (CACHE_ZONE_ALIGN_MASK + 1)) == 0, + "bad zone size"); #define nc_vp n_un.nu_vp #define nc_neg n_un.nu_neg @@ -2785,13 +2787,13 @@ nchinit(void *dummy __unused) u_int i; cache_zone_small = uma_zcreate("S VFS Cache", CACHE_ZONE_SMALL_SIZE, - NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT); + NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGN_MASK, UMA_ZONE_ZINIT); cache_zone_small_ts = uma_zcreate("STS VFS Cache", CACHE_ZONE_SMALL_TS_SIZE, - NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT); + NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGN_MASK, UMA_ZONE_ZINIT); cache_zone_large = uma_zcreate("L VFS Cache", CACHE_ZONE_LARGE_SIZE, - NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT); + NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGN_MASK, UMA_ZONE_ZINIT); cache_zone_large_ts = uma_zcreate("LTS VFS Cache", CACHE_ZONE_LARGE_TS_SIZE, - NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT); + NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGN_MASK, UMA_ZONE_ZINIT); VFS_SMR_ZONE_SET(cache_zone_small); VFS_SMR_ZONE_SET(cache_zone_small_ts);home | help
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