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Commit 4a075e39 authored by Jeff Layton's avatar Jeff Layton
Browse files

locks: add a new struct file_locking_context pointer to struct inode 



The current scheme of using the i_flock list is really difficult to
manage. There is also a legitimate desire for a per-inode spinlock to
manage these lists that isn't the i_lock.

Start conversion to a new scheme to eventually replace the old i_flock
list with a new "file_lock_context" object.

We start by adding a new i_flctx to struct inode. For now, it lives in
parallel with i_flock list, but will eventually replace it. The idea is
to allocate a structure to sit in that pointer and act as a locus for
all things file locking.

We allocate a file_lock_context for an inode when the first lock is
added to it, and it's only freed when the inode is freed. We use the
i_lock to protect the assignment, but afterward it should mostly be
accessed locklessly.

Signed-off-by: default avatarJeff Layton <jlayton@primarydata.com>
Acked-by: default avatarChristoph Hellwig <hch@lst.de>
parent dd459bb1

fs/inode.c

+2 −1
Original line number Diff line number Diff line
@@ -194,7 +194,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode) 
#ifdef CONFIG_FSNOTIFY

	inode->i_fsnotify_mask = 0;

#endif



	inode->i_flctx = NULL;

	this_cpu_inc(nr_inodes);



	return 0;
@@ -237,6 +237,7 @@ void __destroy_inode(struct inode *inode) 
	BUG_ON(inode_has_buffers(inode));

	security_inode_free(inode);

	fsnotify_inode_delete(inode);

	locks_free_lock_context(inode->i_flctx);

	if (!inode->i_nlink) {

		WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);

		atomic_long_dec(&inode->i_sb->s_remove_count);

fs/locks.c

+44 −0
Original line number Diff line number Diff line
@@ -202,8 +202,49 @@ static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS); 
 */

static DEFINE_SPINLOCK(blocked_lock_lock);



static struct kmem_cache *flctx_cache __read_mostly;

static struct kmem_cache *filelock_cache __read_mostly;



static struct file_lock_context *

locks_get_lock_context(struct inode *inode)

{

	struct file_lock_context *new;



	if (likely(inode->i_flctx))

		goto out;



	new = kmem_cache_alloc(flctx_cache, GFP_KERNEL);

	if (!new)

		goto out;



	INIT_LIST_HEAD(&new->flc_flock);



	/*

	 * Assign the pointer if it's not already assigned. If it is, then

	 * free the context we just allocated.

	 */

	spin_lock(&inode->i_lock);

	if (likely(!inode->i_flctx)) {

		inode->i_flctx = new;

		new = NULL;

	}

	spin_unlock(&inode->i_lock);



	if (new)

		kmem_cache_free(flctx_cache, new);

out:

	return inode->i_flctx;

}



void

locks_free_lock_context(struct file_lock_context *ctx)

{

	if (ctx) {

		WARN_ON_ONCE(!list_empty(&ctx->flc_flock));

		kmem_cache_free(flctx_cache, ctx);

	}

}



static void locks_init_lock_heads(struct file_lock *fl)

{

	INIT_HLIST_NODE(&fl->fl_link);
@@ -2636,6 +2677,9 @@ static int __init filelock_init(void) 
{

	int i;



	flctx_cache = kmem_cache_create("file_lock_ctx",

			sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL);



	filelock_cache = kmem_cache_create("file_lock_cache",

			sizeof(struct file_lock), 0, SLAB_PANIC, NULL);

include/linux/fs.h

+11 −0
Original line number Diff line number Diff line
@@ -626,6 +626,7 @@ struct inode { 
#endif

	const struct file_operations	*i_fop;	/* former ->i_op->default_file_ops */

	struct file_lock	*i_flock;

	struct file_lock_context	*i_flctx;

	struct address_space	i_data;

	struct list_head	i_devices;

	union {
@@ -965,6 +966,10 @@ struct file_lock { 
	} fl_u;

};



struct file_lock_context {

	struct list_head	flc_flock;

};



/* The following constant reflects the upper bound of the file/locking space */

#ifndef OFFSET_MAX

#define INT_LIMIT(x)	(~((x)1 << (sizeof(x)*8 - 1)))
@@ -991,6 +996,7 @@ extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg); 
extern int fcntl_getlease(struct file *filp);



/* fs/locks.c */

void locks_free_lock_context(struct file_lock_context *ctx);

void locks_free_lock(struct file_lock *fl);

extern void locks_init_lock(struct file_lock *);

extern struct file_lock * locks_alloc_lock(void);
@@ -1048,6 +1054,11 @@ static inline int fcntl_getlease(struct file *filp) 
	return F_UNLCK;

}



static inline void

locks_free_lock_context(struct file_lock_context *ctx)

{

}



static inline void locks_init_lock(struct file_lock *fl)

{

	return;