NFSv4.1/pnfs: Fix atomicity of commit list updates

This change “NFSv4.1/pnfs: Fix atomicity of commit list updates” in Linux kernel is authored by Trond Myklebust <trond.myklebust [at] primarydata.com> on Fri Jul 31 16:24:30 2015 -0400.

NFSv4.1/pnfs: Fix atomicity of commit list updates

pnfs_layout_mark_request_commit() needs to ensure that it adds the
request to the commit list atomically with all the other updates
in order to prevent corruption to buckets[ds_commit_idx].wlseg
due to races with pnfs_generic_clear_request_commit().

Fixes: 338d00cfef07d ("pnfs: Refactor the *_layout_mark_request_commit...")
Cc: stable@vger.kernel.org # v4.0+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit 86d80f9.

There are 49 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 fs/nfs/internal.h | 15 ++++++++++-----
 fs/nfs/pnfs_nfs.c |  5 +++--
 fs/nfs/write.c    | 29 ++++++++++++++++++++++++-----
 3 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 9b372b8..1dad181 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -490,6 +490,9 @@ void nfs_retry_commit(struct list_head *page_list,
 void nfs_commitdata_release(struct nfs_commit_data *data);
 void nfs_request_add_commit_list(struct nfs_page *req, struct list_head *dst,
 				 struct nfs_commit_info *cinfo);
+void nfs_request_add_commit_list_locked(struct nfs_page *req,
+		struct list_head *dst,
+		struct nfs_commit_info *cinfo);
 void nfs_request_remove_commit_list(struct nfs_page *req,
 				    struct nfs_commit_info *cinfo);
 void nfs_init_cinfo(struct nfs_commit_info *cinfo,
@@ -623,13 +626,15 @@ void nfs_super_set_maxbytes(struct super_block *sb, __u64 maxfilesize)
  * Record the page as unstable and mark its inode as dirty.
  */
 static inline
-void nfs_mark_page_unstable(struct page *page)
+void nfs_mark_page_unstable(struct page *page, struct nfs_commit_info *cinfo)
 {
-	struct inode *inode = page_file_mapping(page)->host;
+	if (!cinfo->dreq) {
+		struct inode *inode = page_file_mapping(page)->host;
 
-	inc_zone_page_state(page, NR_UNSTABLE_NFS);
-	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_RECLAIMABLE);
-	 __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
+		inc_zone_page_state(page, NR_UNSTABLE_NFS);
+		inc_wb_stat(&inode_to_bdi(inode)->wb, WB_RECLAIMABLE);
+		__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
+	}
 }
 
 /*
diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c
index f37e25b..7a28287 100644
--- a/fs/nfs/pnfs_nfs.c
+++ b/fs/nfs/pnfs_nfs.c
@@ -863,9 +863,10 @@ struct nfs4_pnfs_ds_addr *
 	}
 	set_bit(PG_COMMIT_TO_DS, &req->wb_flags);
 	cinfo->ds->nwritten++;
-	spin_unlock(cinfo->lock);
 
-	nfs_request_add_commit_list(req, list, cinfo);
+	nfs_request_add_commit_list_locked(req, list, cinfo);
+	spin_unlock(cinfo->lock);
+	nfs_mark_page_unstable(req->wb_page, cinfo);
 }
 EXPORT_SYMBOL_GPL(pnfs_layout_mark_request_commit);
 
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 75a35a1..fdee927 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -768,6 +768,28 @@ static void nfs_inode_remove_request(struct nfs_page *req)
 }
 
 /**
+ * nfs_request_add_commit_list_locked - add request to a commit list
+ * @req: pointer to a struct nfs_page
+ * @dst: commit list head
+ * @cinfo: holds list lock and accounting info
+ *
+ * This sets the PG_CLEAN bit, updates the cinfo count of
+ * number of outstanding requests requiring a commit as well as
+ * the MM page stats.
+ *
+ * The caller must hold the cinfo->lock, and the nfs_page lock.
+ */
+void
+nfs_request_add_commit_list_locked(struct nfs_page *req, struct list_head *dst,
+			    struct nfs_commit_info *cinfo)
+{
+	set_bit(PG_CLEAN, &req->wb_flags);
+	nfs_list_add_request(req, dst);
+	cinfo->mds->ncommit++;
+}
+EXPORT_SYMBOL_GPL(nfs_request_add_commit_list_locked);
+
+/**
  * nfs_request_add_commit_list - add request to a commit list
  * @req: pointer to a struct nfs_page
  * @dst: commit list head
@@ -784,13 +806,10 @@ static void nfs_inode_remove_request(struct nfs_page *req)
 nfs_request_add_commit_list(struct nfs_page *req, struct list_head *dst,
 			    struct nfs_commit_info *cinfo)
 {
-	set_bit(PG_CLEAN, &(req)->wb_flags);
 	spin_lock(cinfo->lock);
-	nfs_list_add_request(req, dst);
-	cinfo->mds->ncommit++;
+	nfs_request_add_commit_list_locked(req, dst, cinfo);
 	spin_unlock(cinfo->lock);
-	if (!cinfo->dreq)
-		nfs_mark_page_unstable(req->wb_page);
+	nfs_mark_page_unstable(req->wb_page, cinfo);
 }
 EXPORT_SYMBOL_GPL(nfs_request_add_commit_list);
 

The commit for this change in Linux stable tree is 86d80f9 (patch).

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