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: Jeff Layton <jlayton@primarydata.com>
Acked-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Jeff Layton 2015-01-16 15:05:54 -05:00
parent dd459bb197
commit 4a075e39c8
3 changed files with 57 additions and 1 deletions

View File

@ -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);

View File

@ -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);

View File

@ -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;