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Commit 27571297 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent 0847ef88

fs/nfs/pnfs_nfs.c

+32 −18
Original line number Diff line number Diff line
@@ -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);

		}

	}