From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Refactor nfs_lock_and_join_requests() in order to separate out the
subrequest merging into its own function nfs_lock_and_join_group()
that can be used by O_DIRECT.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
fs/nfs/pagelist.c | 26 ++++++-
fs/nfs/write.c | 164 +++++++++++++++++++++++----------------
include/linux/nfs_page.h | 1 +
3 files changed, 123 insertions(+), 68 deletions(-)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index b9805d1dac75..f61f96603df7 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -130,6 +130,25 @@ nfs_async_iocounter_wait(struct rpc_task *task, struct nfs_lock_context *l_ctx)
}
EXPORT_SYMBOL_GPL(nfs_async_iocounter_wait);
+/*
+ * nfs_page_lock_head_request - page lock the head of the page group
+ * @req: any member of the page group
+ */
+struct nfs_page *
+nfs_page_group_lock_head(struct nfs_page *req)
+{
+ struct nfs_page *head = req->wb_head;
+
+ while (!nfs_lock_request(head)) {
+ int ret = nfs_wait_on_request(head);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ }
+ if (head != req)
+ kref_get(&head->wb_kref);
+ return head;
+}
+
/*
* nfs_unroll_locks - unlock all newly locked reqs and wait on @req
* @head: head request of page group, must be holding head lock
@@ -186,14 +205,16 @@ nfs_page_group_lock_subreq(struct nfs_page *head, struct nfs_page *subreq)
* @head: head request of page group
*
* This is a helper function for nfs_lock_and_join_requests which
- * must be called with the head request and page group both locked.
- * On error, it returns with the page group unlocked.
+ * must be called with the head request locked.
*/
int nfs_page_group_lock_subrequests(struct nfs_page *head)
{
struct nfs_page *subreq;
int ret;
+ ret = nfs_page_group_lock(head);
+ if (ret < 0)
+ return ret;
/* lock each request in the page group */
for (subreq = head->wb_this_page; subreq != head;
subreq = subreq->wb_this_page) {
@@ -201,6 +222,7 @@ int nfs_page_group_lock_subrequests(struct nfs_page *head)
if (ret < 0)
return ret;
}
+ nfs_page_group_unlock(head);
return 0;
}
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 832cf57ea442..63b64333c3ea 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -149,6 +149,31 @@ static void nfs_io_completion_put(struct nfs_io_completion *ioc)
kref_put(&ioc->refcount, nfs_io_completion_release);
}
+static void
+nfs_page_set_inode_ref(struct nfs_page *req, struct inode *inode)
+{
+ if (!test_and_set_bit(PG_INODE_REF, &req->wb_flags)) {
+ kref_get(&req->wb_kref);
+ atomic_long_inc(&NFS_I(inode)->nrequests);
+ }
+}
+
+static int
+nfs_cancel_remove_inode(struct nfs_page *req, struct inode *inode)
+{
+ int ret;
+
+ if (!test_bit(PG_REMOVE, &req->wb_flags))
+ return 0;
+ ret = nfs_page_group_lock(req);
+ if (ret)
+ return ret;
+ if (test_and_clear_bit(PG_REMOVE, &req->wb_flags))
+ nfs_page_set_inode_ref(req, inode);
+ nfs_page_group_unlock(req);
+ return 0;
+}
+
static struct nfs_page *
nfs_page_private_request(struct page *page)
{
@@ -218,6 +243,36 @@ static struct nfs_page *nfs_page_find_head_request(struct page *page)
return req;
}
+static struct nfs_page *nfs_find_and_lock_page_request(struct page *page)
+{
+ struct inode *inode = page_file_mapping(page)->host;
+ struct nfs_page *req, *head;
+ int ret;
+
+ for (;;) {
+ req = nfs_page_find_head_request(page);
+ if (!req)
+ return req;
+ head = nfs_page_group_lock_head(req);
+ if (head != req)
+ nfs_release_request(req);
+ if (IS_ERR(head))
+ return head;
+ ret = nfs_cancel_remove_inode(head, inode);
+ if (ret < 0) {
+ nfs_unlock_and_release_request(head);
+ return ERR_PTR(ret);
+ }
+ /* Ensure that nobody removed the request before we locked it */
+ if (head == nfs_page_private_request(page))
+ break;
+ if (PageSwapCache(page))
+ break;
+ nfs_unlock_and_release_request(head);
+ }
+ return head;
+}
+
/* Adjust the file length if we're writing beyond the end */
static void nfs_grow_file(struct page *page, unsigned int offset, unsigned int count)
{
@@ -436,65 +491,22 @@ nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list,
}
/*
- * nfs_lock_and_join_requests - join all subreqs to the head req and return
- * a locked reference, cancelling any pending
- * operations for this page.
- *
- * @page - the page used to lookup the "page group" of nfs_page structures
+ * nfs_join_page_group - destroy subrequests of the head req
+ * @head: the page used to lookup the "page group" of nfs_page structures
+ * @inode: Inode to which the request belongs.
*
* This function joins all sub requests to the head request by first
* locking all requests in the group, cancelling any pending operations
* and finally updating the head request to cover the whole range covered by
* the (former) group. All subrequests are removed from any write or commit
* lists, unlinked from the group and destroyed.
- *
- * Returns a locked, referenced pointer to the head request - which after
- * this call is guaranteed to be the only request associated with the page.
- * Returns NULL if no requests are found for @page, or a ERR_PTR if an
- * error was encountered.
*/
-static struct nfs_page *
-nfs_lock_and_join_requests(struct page *page)
+static void
+nfs_join_page_group(struct nfs_page *head, struct inode *inode)
{
- struct inode *inode = page_file_mapping(page)->host;
- struct nfs_page *head, *subreq;
+ struct nfs_page *subreq;
struct nfs_page *destroy_list = NULL;
unsigned int pgbase, off, bytes;
- int ret;
-
-try_again:
- /*
- * A reference is taken only on the head request which acts as a
- * reference to the whole page group - the group will not be destroyed
- * until the head reference is released.
- */
- head = nfs_page_find_head_request(page);
- if (!head)
- return NULL;
-
- /* lock the page head first in order to avoid an ABBA inefficiency */
- if (!nfs_lock_request(head)) {
- ret = nfs_wait_on_request(head);
- nfs_release_request(head);
- if (ret < 0)
- return ERR_PTR(ret);
- goto try_again;
- }
-
- /* Ensure that nobody removed the request before we locked it */
- if (head != nfs_page_private_request(page) && !PageSwapCache(page)) {
- nfs_unlock_and_release_request(head);
- goto try_again;
- }
-
- ret = nfs_page_group_lock(head);
- if (ret < 0)
- goto release_request;
-
- /* lock each request in the page group */
- ret = nfs_page_group_lock_subrequests(head);
- if (ret < 0)
- goto release_request;
pgbase = head->wb_pgbase;
bytes = head->wb_bytes;
@@ -531,30 +543,50 @@ nfs_lock_and_join_requests(struct page *page)
head->wb_this_page = head;
}
- /* Postpone destruction of this request */
- if (test_and_clear_bit(PG_REMOVE, &head->wb_flags)) {
- set_bit(PG_INODE_REF, &head->wb_flags);
- kref_get(&head->wb_kref);
- atomic_long_inc(&NFS_I(inode)->nrequests);
- }
+ nfs_destroy_unlinked_subrequests(destroy_list, head, inode);
+}
- nfs_page_group_unlock(head);
+/*
+ * nfs_lock_and_join_requests - join all subreqs to the head req
+ * @page: the page used to lookup the "page group" of nfs_page structures
+ *
+ * This function joins all sub requests to the head request by first
+ * locking all requests in the group, cancelling any pending operations
+ * and finally updating the head request to cover the whole range covered by
+ * the (former) group. All subrequests are removed from any write or commit
+ * lists, unlinked from the group and destroyed.
+ *
+ * Returns a locked, referenced pointer to the head request - which after
+ * this call is guaranteed to be the only request associated with the page.
+ * Returns NULL if no requests are found for @page, or a ERR_PTR if an
+ * error was encountered.
+ */
+static struct nfs_page *
+nfs_lock_and_join_requests(struct page *page)
+{
+ struct inode *inode = page_file_mapping(page)->host;
+ struct nfs_page *head;
+ int ret;
- nfs_destroy_unlinked_subrequests(destroy_list, head, inode);
+ /*
+ * A reference is taken only on the head request which acts as a
+ * reference to the whole page group - the group will not be destroyed
+ * until the head reference is released.
+ */
+ head = nfs_find_and_lock_page_request(page);
+ if (IS_ERR_OR_NULL(head))
+ return head;
- /* Did we lose a race with nfs_inode_remove_request()? */
- if (!(PagePrivate(page) || PageSwapCache(page))) {
+ /* lock each request in the page group */
+ ret = nfs_page_group_lock_subrequests(head);
+ if (ret < 0) {
nfs_unlock_and_release_request(head);
- return NULL;
+ return ERR_PTR(ret);
}
- /* still holds ref on head from nfs_page_find_head_request
- * and still has lock on head from lock loop */
- return head;
+ nfs_join_page_group(head, inode);
-release_request:
- nfs_unlock_and_release_request(head);
- return ERR_PTR(ret);
+ return head;
}
static void nfs_write_error(struct nfs_page *req, int error)
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index dd205bc6bc58..99198c039bd6 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -139,6 +139,7 @@ extern size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
extern int nfs_wait_on_request(struct nfs_page *);
extern void nfs_unlock_request(struct nfs_page *req);
extern void nfs_unlock_and_release_request(struct nfs_page *);
+extern struct nfs_page *nfs_page_group_lock_head(struct nfs_page *req);
extern int nfs_page_group_lock_subrequests(struct nfs_page *head);
extern int nfs_page_group_lock(struct nfs_page *);
extern void nfs_page_group_unlock(struct nfs_page *);
--
2.25.1
