Re: [PATCH 11/15] pnfs: change lo refcounting to atomic_t

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On Dec 22, 2010, at 4:47 PM, Trond Myklebust wrote:

> On Tue, 2010-12-21 at 23:00 -0500, Fred Isaman wrote:
>> This will be required to allow us to grab reference outside of i_lock.
>> While we are at it, make put_layout_hdr take the same argument as all the
>> related functions.
>> 
>> Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxx>
>> ---
>> fs/nfs/pnfs.c |   50 ++++++++++++++++++++++++++++----------------------
>> fs/nfs/pnfs.h |    4 ++--
>> 2 files changed, 30 insertions(+), 24 deletions(-)
>> 
>> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
>> index 970cc3b..53a0184 100644
>> --- a/fs/nfs/pnfs.c
>> +++ b/fs/nfs/pnfs.c
>> @@ -177,34 +177,40 @@ EXPORT_SYMBOL_GPL(pnfs_unregister_layoutdriver);
>>  * pNFS client layout cache
>>  */
>> 
>> +/* Need to hold i_lock if caller does not already hold reference */
>> static void
>> -get_layout_hdr_locked(struct pnfs_layout_hdr *lo)
>> +get_layout_hdr(struct pnfs_layout_hdr *lo)
>> {
>> -	assert_spin_locked(&lo->plh_inode->i_lock);
>> -	lo->plh_refcount++;
>> +	atomic_inc(&lo->plh_refcount);
>> }
>> 
>> static void
>> -put_layout_hdr_locked(struct pnfs_layout_hdr *lo)
>> +destroy_layout_hdr(struct pnfs_layout_hdr *lo)
>> {
>> -	assert_spin_locked(&lo->plh_inode->i_lock);
>> -	BUG_ON(lo->plh_refcount == 0);
>> +	dprintk("%s: freeing layout cache %p\n", __func__, lo);
>> +	BUG_ON(!list_empty(&lo->plh_layouts));
>> +	NFS_I(lo->plh_inode)->layout = NULL;
>> +	kfree(lo);
>> +}
>> 
>> -	lo->plh_refcount--;
>> -	if (!lo->plh_refcount) {
>> -		dprintk("%s: freeing layout cache %p\n", __func__, lo);
>> -		BUG_ON(!list_empty(&lo->plh_layouts));
>> -		NFS_I(lo->plh_inode)->layout = NULL;
>> -		kfree(lo);
>> -	}
>> +static void
>> +put_layout_hdr_locked(struct pnfs_layout_hdr *lo)
>> +{
>> +	BUG_ON(atomic_read(&lo->plh_refcount) == 0);
> 
> Isn't this debugged by now?
> 
>> +	if (atomic_dec_and_test(&lo->plh_refcount))
>> +		destroy_layout_hdr(lo);
>> }
>> 
>> void
>> -put_layout_hdr(struct inode *inode)
>> +put_layout_hdr(struct pnfs_layout_hdr *lo)
>> {
>> -	spin_lock(&inode->i_lock);
>> -	put_layout_hdr_locked(NFS_I(inode)->layout);
>> -	spin_unlock(&inode->i_lock);
>> +	struct inode *inode = lo->plh_inode;
>> +
>> +	BUG_ON(atomic_read(&lo->plh_refcount) == 0);
> Ditto....

OK, I'll remove those.

Fred

> 
>> +	if (atomic_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
>> +		destroy_layout_hdr(lo);
>> +		spin_unlock(&inode->i_lock);
>> +	}
>> }
>> 
>> static void
>> @@ -224,7 +230,7 @@ static void free_lseg(struct pnfs_layout_segment *lseg)
>> 	BUG_ON(atomic_read(&lseg->pls_refcount) != 0);
>> 	NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
>> 	/* Matched by get_layout_hdr in pnfs_insert_layout */
>> -	put_layout_hdr(ino);
>> +	put_layout_hdr(NFS_I(ino)->layout);
>> }
>> 
>> /* The use of tmp_list is necessary because pnfs_curr_ld->free_lseg
>> @@ -481,7 +487,7 @@ pnfs_insert_layout(struct pnfs_layout_hdr *lo,
>> 			__func__, lseg, lseg->pls_range.iomode,
>> 			lseg->pls_range.offset, lseg->pls_range.length);
>> 	}
>> -	get_layout_hdr_locked(lo);
>> +	get_layout_hdr(lo);
>> 
>> 	dprintk("%s:Return\n", __func__);
>> }
>> @@ -494,7 +500,7 @@ alloc_init_layout_hdr(struct inode *ino)
>> 	lo = kzalloc(sizeof(struct pnfs_layout_hdr), GFP_KERNEL);
>> 	if (!lo)
>> 		return NULL;
>> -	lo->plh_refcount = 1;
>> +	atomic_set(&lo->plh_refcount, 1);
>> 	INIT_LIST_HEAD(&lo->plh_layouts);
>> 	INIT_LIST_HEAD(&lo->plh_segs);
>> 	lo->plh_inode = ino;
>> @@ -609,7 +615,7 @@ pnfs_update_layout(struct inode *ino,
>> 		goto out_unlock;
>> 	atomic_inc(&lo->plh_outstanding);
>> 
>> -	get_layout_hdr_locked(lo);
>> +	get_layout_hdr(lo);
>> 	if (list_empty(&lo->plh_segs)) {
>> 		/* The lo must be on the clp list if there is any
>> 		 * chance of a CB_LAYOUTRECALL(FILE) coming in.
>> @@ -632,7 +638,7 @@ pnfs_update_layout(struct inode *ino,
>> 		spin_unlock(&ino->i_lock);
>> 	}
>> 	atomic_dec(&lo->plh_outstanding);
>> -	put_layout_hdr(ino);
>> +	put_layout_hdr(lo);
>> out:
>> 	dprintk("%s end, state 0x%lx lseg %p\n", __func__,
>> 		nfsi->layout->plh_flags, lseg);
>> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
>> index 698380d..8aaab56 100644
>> --- a/fs/nfs/pnfs.h
>> +++ b/fs/nfs/pnfs.h
>> @@ -65,7 +65,7 @@ struct pnfs_layoutdriver_type {
>> };
>> 
>> struct pnfs_layout_hdr {
>> -	unsigned long		plh_refcount;
>> +	atomic_t		plh_refcount;
>> 	struct list_head	plh_layouts;   /* other client layouts */
>> 	struct list_head	plh_segs;      /* layout segments list */
>> 	nfs4_stateid		plh_stateid;
>> @@ -147,7 +147,7 @@ void unset_pnfs_layoutdriver(struct nfs_server *);
>> int pnfs_layout_process(struct nfs4_layoutget *lgp);
>> void pnfs_destroy_layout(struct nfs_inode *);
>> void pnfs_destroy_all_layouts(struct nfs_client *);
>> -void put_layout_hdr(struct inode *inode);
>> +void put_layout_hdr(struct pnfs_layout_hdr *lo);
>> int pnfs_choose_layoutget_stateid(nfs4_stateid *dst,
>> 				  struct pnfs_layout_hdr *lo,
>> 				  struct nfs4_state *open_state);
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer
> 
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
> 

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