path: root/fs/nfsd/filecache.c

// SPDX-License-Identifier: GPL-2.0
/*
 * The NFSD open file cache.
 *
 * (c) 2015 - Jeff Layton <jeff.layton@primarydata.com>
 *
 * An nfsd_file object is a per-file collection of open state that binds
 * together:
 *   - a struct file *
 *   - a user credential
 *   - a network namespace
 *   - a read-ahead context
 *   - monitoring for writeback errors
 *
 * nfsd_file objects are reference-counted. Consumers acquire a new
 * object via the nfsd_file_acquire API. They manage their interest in
 * the acquired object, and hence the object's reference count, via
 * nfsd_file_get and nfsd_file_put. There are two varieties of nfsd_file
 * object:
 *
 *  * non-garbage-collected: When a consumer wants to precisely control
 *    the lifetime of a file's open state, it acquires a non-garbage-
 *    collected nfsd_file. The final nfsd_file_put releases the open
 *    state immediately.
 *
 *  * garbage-collected: When a consumer does not control the lifetime
 *    of open state, it acquires a garbage-collected nfsd_file. The
 *    final nfsd_file_put allows the open state to linger for a period
 *    during which it may be re-used.
 */

#include <linux/hash.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/sched.h>
#include <linux/list_lru.h>
#include <linux/fsnotify_backend.h>
#include <linux/fsnotify.h>
#include <linux/seq_file.h>
#include <linux/rhashtable.h>

#include "vfs.h"
#include "nfsd.h"
#include "nfsfh.h"
#include "netns.h"
#include "filecache.h"
#include "trace.h"

#define NFSD_LAUNDRETTE_DELAY		     (2 * HZ)

#define NFSD_FILE_CACHE_UP		     (0)

/* We only care about NFSD_MAY_READ/WRITE for this cache */
#define NFSD_FILE_MAY_MASK	(NFSD_MAY_READ|NFSD_MAY_WRITE)

static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);

struct nfsd_fcache_disposal {
	struct work_struct work;
	spinlock_t lock;
	struct list_head freeme;
};

static struct workqueue_struct *nfsd_filecache_wq __read_mostly;

static struct kmem_cache		*nfsd_file_slab;
static struct kmem_cache		*nfsd_file_mark_slab;
static struct list_lru			nfsd_file_lru;
static unsigned long			nfsd_file_flags;
static struct fsnotify_group		*nfsd_file_fsnotify_group;
static struct delayed_work		nfsd_filecache_laundrette;
static struct rhashtable		nfsd_file_rhash_tbl
						____cacheline_aligned_in_smp;

enum nfsd_file_lookup_type {
	NFSD_FILE_KEY_INODE,
	NFSD_FILE_KEY_FULL,
};

struct nfsd_file_lookup_key {
	struct inode			*inode;
	struct net			*net;
	const struct cred		*cred;
	unsigned char			need;
	bool				gc;
	enum nfsd_file_lookup_type	type;
};

/*
 * The returned hash value is based solely on the address of an in-code
 * inode, a pointer to a slab-allocated object. The entropy in such a
 * pointer is concentrated in its middle bits.
 */
static u32 nfsd_file_inode_hash(const struct inode *inode, u32 seed)
{
	unsigned long ptr = (unsigned long)inode;
	u32 k;

	k = ptr >> L1_CACHE_SHIFT;
	k &= 0x00ffffff;
	return jhash2(&k, 1, seed);
}

/**
 * nfsd_file_key_hashfn - Compute the hash value of a lookup key
 * @data: key on which to compute the hash value
 * @len: rhash table's key_len parameter (unused)
 * @seed: rhash table's random seed of the day
 *
 * Return value:
 *   Computed 32-bit hash value
 */
static u32 nfsd_file_key_hashfn(const void *data, u32 len, u32 seed)
{
	const struct nfsd_file_lookup_key *key = data;

	return nfsd_file_inode_hash(key->inode, seed);
}

/**
 * nfsd_file_obj_hashfn - Compute the hash value of an nfsd_file
 * @data: object on which to compute the hash value
 * @len: rhash table's key_len parameter (unused)
 * @seed: rhash table's random seed of the day