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Commit fd6002e9 authored by Fred Isaman's avatar Fred Isaman Committed by Trond Myklebust
Browse files

pnfs: change layout state seqlock to a spinlock 



This prepares for future changes, where the layout state needs
to change atomically with several other variables.  In particular,
it will need to know if lo->segs is empty, as we test that instead
of manipulating the NFS_LAYOUT_STATEID_SET bit.  Moreover, the
layoutstateid is not really a read-mostly structure, as it is
written almost as often as it is read.

The behavior of pnfs_get_layout_stateid is also slightly changed, so that
it no longer changes the stateid.  Its name is changed to +pnfs_choose_layoutget_stateid.

Signed-off-by: default avatarFred Isaman <iisaman@netapp.com>
Signed-off-by: default avatarBenny Halevy <bhalevy@panasas.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent b7edfaa1

fs/nfs/nfs4xdr.c

+1 −1
Original line number Diff line number Diff line
@@ -1798,7 +1798,7 @@ encode_layoutget(struct xdr_stream *xdr, 
	p = xdr_encode_hyper(p, args->range.offset);

	p = xdr_encode_hyper(p, args->range.length);

	p = xdr_encode_hyper(p, args->minlength);

	pnfs_get_layout_stateid(&stateid, NFS_I(args->inode)->layout,

	pnfs_choose_layoutget_stateid(&stateid, NFS_I(args->inode)->layout,

				args->ctx->state);

	p = xdr_encode_opaque_fixed(p, &stateid.data, NFS4_STATEID_SIZE);

	*p = cpu_to_be32(args->maxcount);

fs/nfs/pnfs.c

+23 −56
Original line number Diff line number Diff line
@@ -258,9 +258,6 @@ pnfs_clear_lseg_list(struct pnfs_layout_hdr *lo, struct list_head *tmp_list) 
	/* List does not take a reference, so no need for put here */

	list_del_init(&lo->plh_layouts);

	spin_unlock(&clp->cl_lock);

	write_seqlock(&lo->plh_seqlock);

	clear_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags);

	write_sequnlock(&lo->plh_seqlock);



	dprintk("%s:Return\n", __func__);

}
@@ -319,69 +316,40 @@ pnfs_destroy_all_layouts(struct nfs_client *clp) 
	}

}



/* update lo->plh_stateid with new if is more recent

 *

 * lo->plh_stateid could be the open stateid, in which case we just use what given.

 */

/* update lo->plh_stateid with new if is more recent */

static void

pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo,

			const nfs4_stateid *new)

{

	nfs4_stateid *old = &lo->plh_stateid;

	bool overwrite = false;



	write_seqlock(&lo->plh_seqlock);

	if (!test_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags) ||

	    memcmp(old->stateid.other, new->stateid.other, sizeof(new->stateid.other)))

		overwrite = true;

	else {

	u32 oldseq, newseq;



		oldseq = be32_to_cpu(old->stateid.seqid);

	oldseq = be32_to_cpu(lo->plh_stateid.stateid.seqid);

	newseq = be32_to_cpu(new->stateid.seqid);

	if ((int)(newseq - oldseq) > 0)

			overwrite = true;

	}

	if (overwrite)

		memcpy(&old->stateid, &new->stateid, sizeof(new->stateid));

	write_sequnlock(&lo->plh_seqlock);

		memcpy(&lo->plh_stateid, &new->stateid, sizeof(new->stateid));

}



static void

pnfs_layout_from_open_stateid(struct pnfs_layout_hdr *lo,

			      struct nfs4_state *state)

int

pnfs_choose_layoutget_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo,

			      struct nfs4_state *open_state)

{

	int seq;

	int status = 0;



	dprintk("--> %s\n", __func__);

	write_seqlock(&lo->plh_seqlock);

	do {

		seq = read_seqbegin(&state->seqlock);

		memcpy(lo->plh_stateid.data, state->stateid.data,

		       sizeof(state->stateid.data));

	} while (read_seqretry(&state->seqlock, seq));

	set_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags);

	write_sequnlock(&lo->plh_seqlock);

	dprintk("<-- %s\n", __func__);

}



void

pnfs_get_layout_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo,

			struct nfs4_state *open_state)

{

	spin_lock(&lo->plh_inode->i_lock);

	if (list_empty(&lo->plh_segs)) {

		int seq;



	dprintk("--> %s\n", __func__);

		do {

		seq = read_seqbegin(&lo->plh_seqlock);

		if (!test_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags)) {

			/* This will trigger retry of the read */

			pnfs_layout_from_open_stateid(lo, open_state);

			seq = read_seqbegin(&open_state->seqlock);

			memcpy(dst->data, open_state->stateid.data,

			       sizeof(open_state->stateid.data));

		} while (read_seqretry(&open_state->seqlock, seq));

	} else

			memcpy(dst->data, lo->plh_stateid.data,

			       sizeof(lo->plh_stateid.data));

	} while (read_seqretry(&lo->plh_seqlock, seq));

		memcpy(dst->data, lo->plh_stateid.data, sizeof(lo->plh_stateid.data));

	spin_unlock(&lo->plh_inode->i_lock);

	dprintk("<-- %s\n", __func__);

	return status;

}



/*
@@ -496,7 +464,6 @@ alloc_init_layout_hdr(struct inode *ino) 
	lo->plh_refcount = 1;

	INIT_LIST_HEAD(&lo->plh_layouts);

	INIT_LIST_HEAD(&lo->plh_segs);

	seqlock_init(&lo->plh_seqlock);

	lo->plh_inode = ino;

	return lo;

}

fs/nfs/pnfs.h

+3 −4
Original line number Diff line number Diff line
@@ -44,7 +44,6 @@ struct pnfs_layout_segment { 
enum {

	NFS_LAYOUT_RO_FAILED = 0,	/* get ro layout failed stop trying */

	NFS_LAYOUT_RW_FAILED,		/* get rw layout failed stop trying */

	NFS_LAYOUT_STATEID_SET,		/* have a valid layout stateid */

};



/* Per-layout driver specific registration structure */
@@ -63,7 +62,6 @@ struct pnfs_layout_hdr { 
	unsigned long		plh_refcount;

	struct list_head	plh_layouts;   /* other client layouts */

	struct list_head	plh_segs;      /* layout segments list */

	seqlock_t		plh_seqlock;   /* Protects the stateid */

	nfs4_stateid		plh_stateid;

	unsigned long		plh_flags;

	struct inode		*plh_inode;
@@ -143,7 +141,8 @@ 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 pnfs_get_layout_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo,

int pnfs_choose_layoutget_stateid(nfs4_stateid *dst,

				  struct pnfs_layout_hdr *lo,

				  struct nfs4_state *open_state);