From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Waiman Long To: Alexander Viro , Jonathan Corbet , "Luis R. Rodriguez" , Kees Cook Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, Linus Torvalds , Jan Kara , "Paul E. McKenney" , Andrew Morton , Ingo Molnar , Miklos Szeredi , Matthew Wilcox , Larry Woodman , James Bottomley , "Wangkai (Kevin C)" , Michal Hocko , Waiman Long Subject: [PATCH v7 6/6] fs/dcache: Allow deconfiguration of negative dentry code to reduce kernel size Date: Thu, 12 Jul 2018 12:46:05 -0400 Message-Id: <1531413965-5401-7-git-send-email-longman@redhat.com> In-Reply-To: <1531413965-5401-1-git-send-email-longman@redhat.com> References: <1531413965-5401-1-git-send-email-longman@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: The tracking and limit of negative dentries in a filesystem is a useful addition. However, for users who want to reduce the kernel size as much as possible, this feature will probably be on the chopping block. To suit those users, a default-y config option DCACHE_LIMIT_NEG_ENTRY is added so that the negative dentry limiting code can be configured out, if necessary. Signed-off-by: Waiman Long --- fs/Kconfig | 10 ++++++++++ fs/dcache.c | 29 +++++++++++++++++++++++------ include/linux/dcache.h | 2 ++ kernel/sysctl.c | 2 ++ 4 files changed, 37 insertions(+), 6 deletions(-) diff --git a/fs/Kconfig b/fs/Kconfig index ac474a6..b521941 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -113,6 +113,16 @@ source "fs/autofs/Kconfig" source "fs/fuse/Kconfig" source "fs/overlayfs/Kconfig" +# +# Track and limit the number of negative dentries allowed in the system. +# +config DCACHE_LIMIT_NEG_ENTRY + bool "Track & limit negative dcache entries" + default y + help + This option enables the tracking and limiting of the total + number of negative dcache entries allowable in the filesystem. + menu "Caches" source "fs/fscache/Kconfig" diff --git a/fs/dcache.c b/fs/dcache.c index 843c8be..dccfe39 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -141,6 +141,7 @@ struct dentry_stat_t dentry_stat = { #define NEG_DENTRY_BATCH (1 << 8) #define NEG_WARN_PERIOD (60 * HZ) /* Print a warning every min */ +#ifdef CONFIG_DCACHE_LIMIT_NEG_ENTRY static struct static_key limit_neg_key = STATIC_KEY_INIT_FALSE; static int neg_dentry_limit_old; int neg_dentry_limit; @@ -156,6 +157,7 @@ struct dentry_stat_t dentry_stat = { unsigned long warn_jiffies; /* Time when last warning is printed */ } ndblk ____cacheline_aligned_in_smp; proc_handler proc_neg_dentry_limit; +#endif /* CONFIG_DCACHE_LIMIT_NEG_ENTRY */ static DEFINE_PER_CPU(long, nr_dentry); static DEFINE_PER_CPU(long, nr_dentry_unused); @@ -200,7 +202,9 @@ static long get_nr_dentry_neg(void) for_each_possible_cpu(i) sum += per_cpu(nr_dentry_neg, i); +#ifdef CONFIG_DCACHE_LIMIT_NEG_ENTRY sum += neg_dentry_nfree_init - ndblk.nfree; +#endif return sum < 0 ? 0 : sum; } @@ -267,6 +271,7 @@ static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char #endif +#ifdef CONFIG_DCACHE_LIMIT_NEG_ENTRY /* * Decrement negative dentry count if applicable. */ @@ -289,12 +294,6 @@ static void __neg_dentry_dec(struct dentry *dentry) } } -static inline void neg_dentry_dec(struct dentry *dentry) -{ - if (unlikely(d_is_negative(dentry))) - __neg_dentry_dec(dentry); -} - /* * Try to decrement the negative dentry free pool by NEG_DENTRY_BATCH. * The actual decrement returned by the function may be smaller. @@ -454,6 +453,20 @@ int proc_neg_dentry_limit(struct ctl_table *ctl, int write, return 0; } EXPORT_SYMBOL_GPL(proc_neg_dentry_limit); +#else /* CONFIG_DCACHE_LIMIT_NEG_ENTRY */ + +static inline void __neg_dentry_dec(struct dentry *dentry) +{ + this_cpu_dec(nr_dentry_neg); +} + +#endif /* CONFIG_DCACHE_LIMIT_NEG_ENTRY */ + +static inline void neg_dentry_dec(struct dentry *dentry) +{ + if (unlikely(d_is_negative(dentry))) + __neg_dentry_dec(dentry); +} static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount) { @@ -642,6 +655,7 @@ static void d_lru_add(struct dentry *dentry) dentry->d_flags |= DCACHE_LRU_LIST; this_cpu_inc(nr_dentry_unused); if (d_is_negative(dentry)) { +#ifdef CONFIG_DCACHE_LIMIT_NEG_ENTRY if (dentry->d_flags & DCACHE_NEW_NEGATIVE) { dentry->d_flags &= ~DCACHE_NEW_NEGATIVE; if (unlikely(neg_dentry_inc(dentry) < 0)) { @@ -658,6 +672,7 @@ static void d_lru_add(struct dentry *dentry) &dentry->d_sb->s_dentry_lru, &dentry->d_lru)); return; } +#endif /* * We don't do limit check for existing negative * dentries. @@ -3431,7 +3446,9 @@ static void __init dcache_init(void) SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT, d_iname); +#ifdef CONFIG_DCACHE_LIMIT_NEG_ENTRY raw_spin_lock_init(&ndblk.nfree_lock); +#endif /* Hash may have been set up in dcache_init_early */ if (!hashdist) diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 934a6d9..11729a1 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -612,10 +612,12 @@ struct name_snapshot { void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); void release_dentry_name_snapshot(struct name_snapshot *); +#ifdef CONFIG_DCACHE_LIMIT_NEG_ENTRY /* * Negative dentry related declarations. */ extern int neg_dentry_limit; extern int neg_dentry_enforce; +#endif #endif /* __LINUX_DCACHE_H */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index a24101e..732c624 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1851,6 +1851,7 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, .proc_handler = proc_dointvec_minmax, .extra1 = &one, }, +#ifdef CONFIG_DCACHE_LIMIT_NEG_ENTRY { .procname = "neg-dentry-limit", .data = &neg_dentry_limit, @@ -1869,6 +1870,7 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, .extra1 = &zero, .extra2 = &one, }, +#endif { } }; -- 1.8.3.1