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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: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Fred Isaman 2011-01-06 11:36:22 +00:00 committed by Trond Myklebust
parent b7edfaa198
commit fd6002e9b8
3 changed files with 26 additions and 60 deletions
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2
fs/nfs/nfs4xdr.c
View File

@ -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);

67
fs/nfs/pnfs.c
View File

@ -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 seq;
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,
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__);
spin_lock(&lo->plh_inode->i_lock);
if (list_empty(&lo->plh_segs)) {
int seq;
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;
}

5
fs/nfs/pnfs.h
View File

@ -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);