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pNFS: Tighten up locking around DS commit buckets

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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>
This commit is contained in:
Trond Myklebust 2015-08-03 17:38:33 -04:00
parent 0847ef88c3
commit 27571297a7
1 changed files with 32 additions and 18 deletions
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50
fs/nfs/pnfs_nfs.c
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@ -124,11 +124,12 @@ pnfs_generic_scan_ds_commit_list(struct pnfs_commit_bucket *bucket,
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 @@ static void pnfs_generic_retry_commit(struct nfs_commit_info *cinfo, int idx)
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 @@ pnfs_generic_alloc_ds_commits(struct nfs_commit_info *cinfo,
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 @@ pnfs_generic_alloc_ds_commits(struct nfs_commit_info *cinfo,
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 @@ pnfs_generic_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
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 @@ pnfs_generic_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
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);
}
}