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locks: add a new struct file_locking_context pointer to struct inode

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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
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44
fs/locks.c
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@@ -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);