[PATCH 3/4] NFS: Fix the 'desynchronized value of nfs_i.ncommit' error

Trond Myklebust
2007-04-18T01:48:09Z

From: Trond Myklebust <Trond.Myklebust@netapp.com>

Redirtying a request that is already marked for commit will screw up the
accounting for NR_UNSTABLE_NFS as well as nfs_i.ncommit.
Ensure that all requests on the commit queue are labelled with the
PG_NEED_COMMIT flag, and avoid moving them onto the dirty list inside
nfs_page_mark_flush().

Also inline nfs_mark_request_dirty() into nfs_page_mark_flush() for
atomicity reasons. Avoid dropping the spinlock until we're done marking the
request in the radix tree and have added it to the ->dirty list.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---

fs/nfs/write.c | 47 ++++++++++++++++++++++-------------------------
1 files changed, 22 insertions(+), 25 deletions(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 8e94246..ce5b4a9 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -38,7 +38,6 @@
static struct nfs_page * nfs_update_request(struct nfs_open_context*,
struct page *,
unsigned int, unsigned int);
-static void nfs_mark_request_dirty(struct nfs_page *req);
static long nfs_flush_mapping(struct address_space *mapping, struct writeback_control *wbc, int how);
static const struct rpc_call_ops nfs_write_partial_ops;
static const struct rpc_call_ops nfs_write_full_ops;
@@ -255,7 +254,8 @@ static void nfs_end_page_writeback(struct page *page)
static int nfs_page_mark_flush(struct page *page)
{
struct nfs_page *req;
- spinlock_t *req_lock = &NFS_I(page->mapping->host)->req_lock;
+ struct nfs_inode *nfsi = NFS_I(page->mapping->host);
+ spinlock_t *req_lock = &nfsi->req_lock;
int ret;

spin_lock(req_lock);
@@ -279,11 +279,23 @@ static int nfs_page_mark_flush(struct page *page)
return ret;
spin_lock(req_lock);
}
- spin_unlock(req_lock);
+ if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {
+ /* This request is marked for commit */
+ spin_unlock(req_lock);
+ nfs_unlock_request(req);
+ return 1;
+ }
if (nfs_set_page_writeback(page) == 0) {
nfs_list_remove_request(req);
- nfs_mark_request_dirty(req);
- }
+ /* add the request to the inode's dirty list. */
+ radix_tree_tag_set(&nfsi->nfs_page_tree,
+ req->wb_index, NFS_PAGE_TAG_DIRTY);
+ nfs_list_add_request(req, &nfsi->dirty);
+ nfsi->ndirty++;
+ spin_unlock(req_lock);
+ __mark_inode_dirty(page->mapping->host, I_DIRTY_PAGES);
+ } else
+ spin_unlock(req_lock);
ret = test_bit(PG_NEED_FLUSH, &req->wb_flags);
nfs_unlock_request(req);
return ret;
@@ -406,24 +418,6 @@ static void nfs_inode_remove_request(struct nfs_page *req)
nfs_release_request(req);
}

-/*
- * Add a request to the inode's dirty list.
- */
-static void
-nfs_mark_request_dirty(struct nfs_page *req)
-{
- struct inode *inode = req->wb_context->dentry->d_inode;
- struct nfs_inode *nfsi = NFS_I(inode);
-
- spin_lock(&nfsi->req_lock);
- radix_tree_tag_set(&nfsi->nfs_page_tree,
- req->wb_index, NFS_PAGE_TAG_DIRTY);
- nfs_list_add_request(req, &nfsi->dirty);
- nfsi->ndirty++;
- spin_unlock(&nfsi->req_lock);
- __mark_inode_dirty(inode, I_DIRTY_PAGES);
-}
-
static void
nfs_redirty_request(struct nfs_page *req)
{
@@ -438,7 +432,7 @@ nfs_dirty_request(struct nfs_page *req)
{
struct page *page = req->wb_page;

- if (page == NULL)
+ if (page == NULL || test_bit(PG_NEED_COMMIT, &req->wb_flags))
return 0;
return !PageWriteback(req->wb_page);
}
@@ -456,6 +450,7 @@ nfs_mark_request_commit(struct nfs_page *req)
spin_lock(&nfsi->req_lock);
nfs_list_add_request(req, &nfsi->commit);
nfsi->ncommit++;
+ set_bit(PG_NEED_COMMIT, &(req)->wb_flags);
spin_unlock(&nfsi->req_lock);
inc_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
@@ -470,7 +465,7 @@ int nfs_write_need_commit(struct nfs_write_data *data)
static inline
int nfs_reschedule_unstable_write(struct nfs_page *req)
{
- if (test_and_clear_bit(PG_NEED_COMMIT, &req->wb_flags)) {
+ if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {
nfs_mark_request_commit(req);
return 1;
}
@@ -557,6 +552,7 @@ static void nfs_cancel_commit_list(struct list_head *head)
req = nfs_list_entry(head->next);
dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
nfs_list_remove_request(req);
+ clear_bit(PG_NEED_COMMIT, &(req)->wb_flags);
nfs_inode_remove_request(req);
nfs_unlock_request(req);
}
@@ -1295,6 +1291,7 @@ static void nfs_commit_done(struct rpc_task *task, void *calldata)
while (!list_empty(&data->pages)) {
req = nfs_list_entry(data->pages.next);
nfs_list_remove_request(req);
+ clear_bit(PG_NEED_COMMIT, &(req)->wb_flags);
dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);

dprintk("NFS: commit (%s/%Ld %d@%Ld)",