pNFS: Tighten up locking around DS commit buckets
I'm not aware of any bugreports around this issue, but the locking
around the pnfs_commit_bucket is inconsistent at best. This patch
tightens it up by ensuring that the 'bucket->committing' list is always
changed atomically w.r.t. the 'bucket->clseg' layout segment tracking.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c
index 7a28287..cd3c040 100644
--- a/fs/nfs/pnfs_nfs.c
+++ b/fs/nfs/pnfs_nfs.c
@@ -124,11 +124,12 @@
if (ret) {
cinfo->ds->nwritten -= ret;
cinfo->ds->ncommitting += ret;
- bucket->clseg = bucket->wlseg;
- if (list_empty(src))
+ if (bucket->clseg == NULL)
+ bucket->clseg = pnfs_get_lseg(bucket->wlseg);
+ if (list_empty(src)) {
+ pnfs_put_lseg_locked(bucket->wlseg);
bucket->wlseg = NULL;
- else
- pnfs_get_lseg(bucket->clseg);
+ }
}
return ret;
}
@@ -182,19 +183,23 @@
struct pnfs_ds_commit_info *fl_cinfo = cinfo->ds;
struct pnfs_commit_bucket *bucket;
struct pnfs_layout_segment *freeme;
+ LIST_HEAD(pages);
int i;
+ spin_lock(cinfo->lock);
for (i = idx; i < fl_cinfo->nbuckets; i++) {
bucket = &fl_cinfo->buckets[i];
if (list_empty(&bucket->committing))
continue;
- nfs_retry_commit(&bucket->committing, bucket->clseg, cinfo, i);
- spin_lock(cinfo->lock);
freeme = bucket->clseg;
bucket->clseg = NULL;
+ list_splice_init(&bucket->committing, &pages);
spin_unlock(cinfo->lock);
+ nfs_retry_commit(&pages, freeme, cinfo, i);
pnfs_put_lseg(freeme);
+ spin_lock(cinfo->lock);
}
+ spin_unlock(cinfo->lock);
}
static unsigned int
@@ -216,10 +221,6 @@
if (!data)
break;
data->ds_commit_index = i;
- spin_lock(cinfo->lock);
- data->lseg = bucket->clseg;
- bucket->clseg = NULL;
- spin_unlock(cinfo->lock);
list_add(&data->pages, list);
nreq++;
}
@@ -229,6 +230,22 @@
return nreq;
}
+static inline
+void pnfs_fetch_commit_bucket_list(struct list_head *pages,
+ struct nfs_commit_data *data,
+ struct nfs_commit_info *cinfo)
+{
+ struct pnfs_commit_bucket *bucket;
+
+ bucket = &cinfo->ds->buckets[data->ds_commit_index];
+ spin_lock(cinfo->lock);
+ list_splice_init(pages, &bucket->committing);
+ data->lseg = bucket->clseg;
+ bucket->clseg = NULL;
+ spin_unlock(cinfo->lock);
+
+}
+
/* This follows nfs_commit_list pretty closely */
int
pnfs_generic_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
@@ -243,7 +260,7 @@
if (!list_empty(mds_pages)) {
data = nfs_commitdata_alloc();
if (data != NULL) {
- data->lseg = NULL;
+ data->ds_commit_index = -1;
list_add(&data->pages, &list);
nreq++;
} else {
@@ -265,19 +282,16 @@
list_for_each_entry_safe(data, tmp, &list, pages) {
list_del_init(&data->pages);
- if (!data->lseg) {
+ if (data->ds_commit_index < 0) {
nfs_init_commit(data, mds_pages, NULL, cinfo);
nfs_initiate_commit(NFS_CLIENT(inode), data,
NFS_PROTO(data->inode),
data->mds_ops, how, 0);
} else {
- struct pnfs_commit_bucket *buckets;
+ LIST_HEAD(pages);
- buckets = cinfo->ds->buckets;
- nfs_init_commit(data,
- &buckets[data->ds_commit_index].committing,
- data->lseg,
- cinfo);
+ pnfs_fetch_commit_bucket_list(&pages, data, cinfo);
+ nfs_init_commit(data, &pages, data->lseg, cinfo);
initiate_commit(data, how);
}
}
