From: Peter Zijlstra Date: Wed, 16 Apr 2025 16:29:17 +0000 (+0200) Subject: futex: Implement FUTEX2_MPOL X-Git-Tag: v6.16-rc1~199^2^2~15 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c042c505210dc3453f378df432c10fff3d471bc5;p=thirdparty%2Fkernel%2Flinux.git futex: Implement FUTEX2_MPOL Extend the futex2 interface to be aware of mempolicy. When FUTEX2_MPOL is specified and there is a MPOL_PREFERRED or home_node specified covering the futex address, use that hash-map. Notably, in this case the futex will go to the global node hashtable, even if it is a PRIVATE futex. When FUTEX2_NUMA|FUTEX2_MPOL is specified and the user specified node value is FUTEX_NO_NODE, the MPOL lookup (as described above) will be tried first before reverting to setting node to the local node. [bigeasy: add CONFIG_FUTEX_MPOL, add MPOL to FUTEX2_VALID_MASK, write the node only to user if FUTEX_NO_NODE was supplied] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250416162921.513656-18-bigeasy@linutronix.de --- diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index 4706c67699027..e0eddfd306ef3 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -7,6 +7,7 @@ #include #include #include +#include #define MMAP_LOCK_INITIALIZER(name) \ .mmap_lock = __RWSEM_INITIALIZER((name).mmap_lock), @@ -211,6 +212,9 @@ static inline void mmap_read_unlock(struct mm_struct *mm) up_read(&mm->mmap_lock); } +DEFINE_GUARD(mmap_read_lock, struct mm_struct *, + mmap_read_lock(_T), mmap_read_unlock(_T)) + static inline void mmap_read_unlock_non_owner(struct mm_struct *mm) { __mmap_lock_trace_released(mm, false); diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h index 6b94da467e705..7e2744ec89336 100644 --- a/include/uapi/linux/futex.h +++ b/include/uapi/linux/futex.h @@ -63,7 +63,7 @@ #define FUTEX2_SIZE_U32 0x02 #define FUTEX2_SIZE_U64 0x03 #define FUTEX2_NUMA 0x04 - /* 0x08 */ +#define FUTEX2_MPOL 0x08 /* 0x10 */ /* 0x20 */ /* 0x40 */ diff --git a/init/Kconfig b/init/Kconfig index 4b84da2b2ec45..b373267ba2e2b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1704,6 +1704,11 @@ config FUTEX_PRIVATE_HASH depends on FUTEX && !BASE_SMALL && MMU default y +config FUTEX_MPOL + bool + depends on FUTEX && NUMA + default y + config EPOLL bool "Enable eventpoll support" if EXPERT default y diff --git a/kernel/futex/core.c b/kernel/futex/core.c index 1490e6492993e..19a2c65f3d373 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -43,6 +43,8 @@ #include #include #include +#include +#include #include "futex.h" #include "../locking/rtmutex_common.h" @@ -328,6 +330,75 @@ struct futex_hash_bucket *futex_hash(union futex_key *key) #endif /* CONFIG_FUTEX_PRIVATE_HASH */ +#ifdef CONFIG_FUTEX_MPOL + +static int __futex_key_to_node(struct mm_struct *mm, unsigned long addr) +{ + struct vm_area_struct *vma = vma_lookup(mm, addr); + struct mempolicy *mpol; + int node = FUTEX_NO_NODE; + + if (!vma) + return FUTEX_NO_NODE; + + mpol = vma_policy(vma); + if (!mpol) + return FUTEX_NO_NODE; + + switch (mpol->mode) { + case MPOL_PREFERRED: + node = first_node(mpol->nodes); + break; + case MPOL_PREFERRED_MANY: + case MPOL_BIND: + if (mpol->home_node != NUMA_NO_NODE) + node = mpol->home_node; + break; + default: + break; + } + + return node; +} + +static int futex_key_to_node_opt(struct mm_struct *mm, unsigned long addr) +{ + int seq, node; + + guard(rcu)(); + + if (!mmap_lock_speculate_try_begin(mm, &seq)) + return -EBUSY; + + node = __futex_key_to_node(mm, addr); + + if (mmap_lock_speculate_retry(mm, seq)) + return -EAGAIN; + + return node; +} + +static int futex_mpol(struct mm_struct *mm, unsigned long addr) +{ + int node; + + node = futex_key_to_node_opt(mm, addr); + if (node >= FUTEX_NO_NODE) + return node; + + guard(mmap_read_lock)(mm); + return __futex_key_to_node(mm, addr); +} + +#else /* !CONFIG_FUTEX_MPOL */ + +static int futex_mpol(struct mm_struct *mm, unsigned long addr) +{ + return FUTEX_NO_NODE; +} + +#endif /* CONFIG_FUTEX_MPOL */ + /** * __futex_hash - Return the hash bucket * @key: Pointer to the futex key for which the hash is calculated @@ -342,18 +413,20 @@ struct futex_hash_bucket *futex_hash(union futex_key *key) static struct futex_hash_bucket * __futex_hash(union futex_key *key, struct futex_private_hash *fph) { - struct futex_hash_bucket *hb; + int node = key->both.node; u32 hash; - int node; - hb = __futex_hash_private(key, fph); - if (hb) - return hb; + if (node == FUTEX_NO_NODE) { + struct futex_hash_bucket *hb; + + hb = __futex_hash_private(key, fph); + if (hb) + return hb; + } hash = jhash2((u32 *)key, offsetof(typeof(*key), both.offset) / sizeof(u32), key->both.offset); - node = key->both.node; if (node == FUTEX_NO_NODE) { /* @@ -480,6 +553,7 @@ int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key, struct folio *folio; struct address_space *mapping; int node, err, size, ro = 0; + bool node_updated = false; bool fshared; fshared = flags & FLAGS_SHARED; @@ -501,27 +575,37 @@ int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key, if (unlikely(should_fail_futex(fshared))) return -EFAULT; + node = FUTEX_NO_NODE; + if (flags & FLAGS_NUMA) { u32 __user *naddr = (void *)uaddr + size / 2; if (futex_get_value(&node, naddr)) return -EFAULT; - if (node == FUTEX_NO_NODE) { - node = numa_node_id(); - if (futex_put_value(node, naddr)) - return -EFAULT; - - } else if (node >= MAX_NUMNODES || !node_possible(node)) { + if (node != FUTEX_NO_NODE && + (node >= MAX_NUMNODES || !node_possible(node))) return -EINVAL; - } + } - key->both.node = node; + if (node == FUTEX_NO_NODE && (flags & FLAGS_MPOL)) { + node = futex_mpol(mm, address); + node_updated = true; + } - } else { - key->both.node = FUTEX_NO_NODE; + if (flags & FLAGS_NUMA) { + u32 __user *naddr = (void *)uaddr + size / 2; + + if (node == FUTEX_NO_NODE) { + node = numa_node_id(); + node_updated = true; + } + if (node_updated && futex_put_value(node, naddr)) + return -EFAULT; } + key->both.node = node; + /* * PROCESS_PRIVATE futexes are fast. * As the mm cannot disappear under us and the 'key' only needs diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h index acc7953678898..069fc2a83080d 100644 --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -39,6 +39,7 @@ #define FLAGS_HAS_TIMEOUT 0x0040 #define FLAGS_NUMA 0x0080 #define FLAGS_STRICT 0x0100 +#define FLAGS_MPOL 0x0200 /* FUTEX_ to FLAGS_ */ static inline unsigned int futex_to_flags(unsigned int op) @@ -54,7 +55,7 @@ static inline unsigned int futex_to_flags(unsigned int op) return flags; } -#define FUTEX2_VALID_MASK (FUTEX2_SIZE_MASK | FUTEX2_NUMA | FUTEX2_PRIVATE) +#define FUTEX2_VALID_MASK (FUTEX2_SIZE_MASK | FUTEX2_NUMA | FUTEX2_MPOL | FUTEX2_PRIVATE) /* FUTEX2_ to FLAGS_ */ static inline unsigned int futex2_to_flags(unsigned int flags2) @@ -67,6 +68,9 @@ static inline unsigned int futex2_to_flags(unsigned int flags2) if (flags2 & FUTEX2_NUMA) flags |= FLAGS_NUMA; + if (flags2 & FUTEX2_MPOL) + flags |= FLAGS_MPOL; + return flags; }