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linux_dsm_epyc7002/include/linux/dcache.h
Linus Torvalds 8aab6a2733 vfs: reorganize dput() memory accesses 
This is me being a bit OCD after all the dentry optimization work this
merge window: profiles end up showing 'dput()' as a rather expensive
operation, and there were two unrelated bad reasons for that.

The first reason was reading d_lockref.count for debugging purposes,
which touches the lockref cacheline (for reads) before really need to.
More importantly, the debugging test in question is _wrong_, and has
hidden bugs.  It's true that we can only sleep when the count goes down
to zero, but the test as-is hides the much more subtle bug that happens
if we race with somebody else deleting the file.

Anyway we _will_ touch that cacheline, but let's do it for a write and
in the right routine (ie in "lockref_put_or_lock()") which annotates the
costs better.  So remove the misleading debug code.

The other was an unnecessary access to the cacheline that contains the
d_lru list, just to check whether we already were on the LRU list or
not.  This is exactly what we have d_flags for, so that we can avoid
touching extra cache lines for the common case.  So just add another bit
for "is this dentry on the LRU".

Finally, mark the tests properly likely/unlikely, so that the common
fast-paths are dense in the instruction stream.

This makes the profiles look much saner.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-08 13:26:18 -07:00

399 lines
12 KiB
C
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#ifndef __LINUX_DCACHE_H
#define __LINUX_DCACHE_H
#include <linux/atomic.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/rculist_bl.h>
#include <linux/spinlock.h>
#include <linux/seqlock.h>
#include <linux/cache.h>
#include <linux/rcupdate.h>
#include <linux/lockref.h>
struct nameidata;
struct path;
struct vfsmount;
/*
* linux/include/linux/dcache.h
*
* Dirent cache data structures
*
* (C) Copyright 1997 Thomas Schoebel-Theuer,
* with heavy changes by Linus Torvalds
*/
#define IS_ROOT(x) ((x) == (x)->d_parent)
/* The hash is always the low bits of hash_len */
#ifdef __LITTLE_ENDIAN
#define HASH_LEN_DECLARE u32 hash; u32 len;
#else
#define HASH_LEN_DECLARE u32 len; u32 hash;
#endif
/*
* "quick string" -- eases parameter passing, but more importantly
* saves "metadata" about the string (ie length and the hash).
*
* hash comes first so it snuggles against d_parent in the
* dentry.
*/
struct qstr {
union {
struct {
HASH_LEN_DECLARE;
};
u64 hash_len;
};
const unsigned char *name;
};
#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
#define hashlen_hash(hashlen) ((u32) (hashlen))
#define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
struct dentry_stat_t {
int nr_dentry;
int nr_unused;
int age_limit; /* age in seconds */
int want_pages; /* pages requested by system */
int dummy[2];
};
extern struct dentry_stat_t dentry_stat;
/* Name hashing routines. Initial hash value */
/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
#define init_name_hash() 0
/* partial hash update function. Assume roughly 4 bits per character */
static inline unsigned long
partial_name_hash(unsigned long c, unsigned long prevhash)
{
return (prevhash + (c << 4) + (c >> 4)) * 11;
}
/*
* Finally: cut down the number of bits to a int value (and try to avoid
* losing bits)
*/
static inline unsigned long end_name_hash(unsigned long hash)
{
return (unsigned int) hash;
}
/* Compute the hash for a name string. */
extern unsigned int full_name_hash(const unsigned char *, unsigned int);
/*
* Try to keep struct dentry aligned on 64 byte cachelines (this will
* give reasonable cacheline footprint with larger lines without the
* large memory footprint increase).
*/
#ifdef CONFIG_64BIT
# define DNAME_INLINE_LEN 32 /* 192 bytes */
#else
# ifdef CONFIG_SMP
# define DNAME_INLINE_LEN 36 /* 128 bytes */
# else
# define DNAME_INLINE_LEN 40 /* 128 bytes */
# endif
#endif
#define d_lock d_lockref.lock
struct dentry {
/* RCU lookup touched fields */
unsigned int d_flags; /* protected by d_lock */
seqcount_t d_seq; /* per dentry seqlock */
struct hlist_bl_node d_hash; /* lookup hash list */
struct dentry *d_parent; /* parent directory */
struct qstr d_name;
struct inode *d_inode; /* Where the name belongs to - NULL is
* negative */
unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
/* Ref lookup also touches following */
struct lockref d_lockref; /* per-dentry lock and refcount */
const struct dentry_operations *d_op;
struct super_block *d_sb; /* The root of the dentry tree */
unsigned long d_time; /* used by d_revalidate */
void *d_fsdata; /* fs-specific data */
struct list_head d_lru; /* LRU list */
/*
* d_child and d_rcu can share memory
*/
union {
struct list_head d_child; /* child of parent list */
struct rcu_head d_rcu;
} d_u;
struct list_head d_subdirs; /* our children */
struct hlist_node d_alias; /* inode alias list */
};
/*
* dentry->d_lock spinlock nesting subclasses:
*
* 0: normal
* 1: nested
*/
enum dentry_d_lock_class
{
DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
DENTRY_D_LOCK_NESTED
};
struct dentry_operations {
int (*d_revalidate)(struct dentry *, unsigned int);
int (*d_weak_revalidate)(struct dentry *, unsigned int);
int (*d_hash)(const struct dentry *, struct qstr *);
int (*d_compare)(const struct dentry *, const struct dentry *,
unsigned int, const char *, const struct qstr *);
int (*d_delete)(const struct dentry *);
void (*d_release)(struct dentry *);
void (*d_prune)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(struct dentry *, bool);
} ____cacheline_aligned;
/*
* Locking rules for dentry_operations callbacks are to be found in
* Documentation/filesystems/Locking. Keep it updated!
*
* FUrther descriptions are found in Documentation/filesystems/vfs.txt.
* Keep it updated too!
*/
/* d_flags entries */
#define DCACHE_OP_HASH 0x0001
#define DCACHE_OP_COMPARE 0x0002
#define DCACHE_OP_REVALIDATE 0x0004
#define DCACHE_OP_DELETE 0x0008
#define DCACHE_OP_PRUNE 0x0010
#define DCACHE_DISCONNECTED 0x0020
/* This dentry is possibly not currently connected to the dcache tree, in
* which case its parent will either be itself, or will have this flag as
* well. nfsd will not use a dentry with this bit set, but will first
* endeavour to clear the bit either by discovering that it is connected,
* or by performing lookup operations. Any filesystem which supports
* nfsd_operations MUST have a lookup function which, if it finds a
* directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
* dentry into place and return that dentry rather than the passed one,
* typically using d_splice_alias. */
#define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */
#define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */
#define DCACHE_CANT_MOUNT 0x0100
#define DCACHE_GENOCIDE 0x0200
#define DCACHE_SHRINK_LIST 0x0400
#define DCACHE_OP_WEAK_REVALIDATE 0x0800
#define DCACHE_NFSFS_RENAMED 0x1000
/* this dentry has been "silly renamed" and has to be deleted on the last
* dput() */
#define DCACHE_COOKIE 0x2000 /* For use by dcookie subsystem */
#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
/* Parent inode is watched by some fsnotify listener */
#define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
#define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
#define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
#define DCACHE_MANAGED_DENTRY \
(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
#define DCACHE_LRU_LIST 0x80000
#define DCACHE_DENTRY_KILLED 0x100000
extern seqlock_t rename_lock;
static inline int dname_external(const struct dentry *dentry)
{
return dentry->d_name.name != dentry->d_iname;
}
/*
* These are the low-level FS interfaces to the dcache..
*/
extern void d_instantiate(struct dentry *, struct inode *);
extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
extern void __d_drop(struct dentry *dentry);
extern void d_drop(struct dentry *dentry);
extern void d_delete(struct dentry *);
extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
/* allocate/de-allocate */
extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
extern struct dentry *d_find_any_alias(struct inode *inode);
extern struct dentry * d_obtain_alias(struct inode *);
extern void shrink_dcache_sb(struct super_block *);
extern void shrink_dcache_parent(struct dentry *);
extern void shrink_dcache_for_umount(struct super_block *);
extern int d_invalidate(struct dentry *);
/* only used at mount-time */
extern struct dentry * d_make_root(struct inode *);
/* <clickety>-<click> the ramfs-type tree */
extern void d_genocide(struct dentry *);
extern void d_tmpfile(struct dentry *, struct inode *);
extern struct dentry *d_find_alias(struct inode *);
extern void d_prune_aliases(struct inode *);
/* test whether we have any submounts in a subdir tree */
extern int have_submounts(struct dentry *);
extern int check_submounts_and_drop(struct dentry *);
/*
* This adds the entry to the hash queues.
*/
extern void d_rehash(struct dentry *);
/**
* d_add - add dentry to hash queues
* @entry: dentry to add
* @inode: The inode to attach to this dentry
*
* This adds the entry to the hash queues and initializes @inode.
* The entry was actually filled in earlier during d_alloc().
*/
static inline void d_add(struct dentry *entry, struct inode *inode)
{
d_instantiate(entry, inode);
d_rehash(entry);
}
/**
* d_add_unique - add dentry to hash queues without aliasing
* @entry: dentry to add
* @inode: The inode to attach to this dentry
*
* This adds the entry to the hash queues and initializes @inode.
* The entry was actually filled in earlier during d_alloc().
*/
static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
{
struct dentry *res;
res = d_instantiate_unique(entry, inode);
d_rehash(res != NULL ? res : entry);
return res;
}
extern void dentry_update_name_case(struct dentry *, struct qstr *);
/* used for rename() and baskets */
extern void d_move(struct dentry *, struct dentry *);
extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
/* appendix may either be NULL or be used for transname suffixes */
extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
const struct qstr *name, unsigned *seq);
static inline unsigned d_count(const struct dentry *dentry)
{
return dentry->d_lockref.count;
}
/* validate "insecure" dentry pointer */
extern int d_validate(struct dentry *, struct dentry *);
/*
* helper function for dentry_operations.d_dname() members
*/
extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
extern char *simple_dname(struct dentry *, char *, int);
extern char *__d_path(const struct path *, const struct path *, char *, int);
extern char *d_absolute_path(const struct path *, char *, int);
extern char *d_path(const struct path *, char *, int);
extern char *dentry_path_raw(struct dentry *, char *, int);
extern char *dentry_path(struct dentry *, char *, int);
/* Allocation counts.. */
/**
* dget, dget_dlock - get a reference to a dentry
* @dentry: dentry to get a reference to
*
* Given a dentry or %NULL pointer increment the reference count
* if appropriate and return the dentry. A dentry will not be
* destroyed when it has references.
*/
static inline struct dentry *dget_dlock(struct dentry *dentry)
{
if (dentry)
dentry->d_lockref.count++;
return dentry;
}
static inline struct dentry *dget(struct dentry *dentry)
{
if (dentry)
lockref_get(&dentry->d_lockref);
return dentry;
}
extern struct dentry *dget_parent(struct dentry *dentry);
/**
* d_unhashed - is dentry hashed
* @dentry: entry to check
*
* Returns true if the dentry passed is not currently hashed.
*/
static inline int d_unhashed(const struct dentry *dentry)
{
return hlist_bl_unhashed(&dentry->d_hash);
}
static inline int d_unlinked(const struct dentry *dentry)
{
return d_unhashed(dentry) && !IS_ROOT(dentry);
}
static inline int cant_mount(const struct dentry *dentry)
{
return (dentry->d_flags & DCACHE_CANT_MOUNT);
}
static inline void dont_mount(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
dentry->d_flags |= DCACHE_CANT_MOUNT;
spin_unlock(&dentry->d_lock);
}
extern void dput(struct dentry *);
static inline bool d_managed(const struct dentry *dentry)
{
return dentry->d_flags & DCACHE_MANAGED_DENTRY;
}
static inline bool d_mountpoint(const struct dentry *dentry)
{
return dentry->d_flags & DCACHE_MOUNTED;
}
extern int sysctl_vfs_cache_pressure;
#endif /* __LINUX_DCACHE_H */
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