Change nfs_find_and_lock_request so nfs_page_async_flush can handle multiple
requests in a page. There is only one request for a page the first time
nfs_page_async_flush is called, but if a write or commit fails, async_flush
is called again and there may be multiple requests associated with the page.
The solution is to merge all the requests in a page group into a single
request before calling nfs_pageio_add_request.
Rename nfs_find_and_lock_request to nfs_lock_and_join_requests and
change it to first lock all requests for the page, then cancel and merge
all subrequests into the head request.
Signed-off-by: Weston Andros Adamson <dros@xxxxxxxxxxxxxxx>
---
fs/nfs/internal.h | 1 +
fs/nfs/pagelist.c | 4 +-
fs/nfs/write.c | 254 +++++++++++++++++++++++++++++++++++++++++++++++++-----
3 files changed, 234 insertions(+), 25 deletions(-)
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index da36257..2f19e83 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -244,6 +244,7 @@ void nfs_pgio_data_destroy(struct nfs_pgio_header *);
int nfs_generic_pgio(struct nfs_pageio_descriptor *, struct nfs_pgio_header *);
int nfs_initiate_pgio(struct rpc_clnt *, struct nfs_pgio_header *,
const struct rpc_call_ops *, int, int);
+void nfs_free_request(struct nfs_page *req);
static inline void nfs_iocounter_init(struct nfs_io_counter *c)
{
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 8b074da..a22c130 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -29,8 +29,6 @@
static struct kmem_cache *nfs_page_cachep;
static const struct rpc_call_ops nfs_pgio_common_ops;
-static void nfs_free_request(struct nfs_page *);
-
static bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount)
{
p->npages = pagecount;
@@ -406,7 +404,7 @@ static void nfs_clear_request(struct nfs_page *req)
*
* Note: Should never be called with the spinlock held!
*/
-static void nfs_free_request(struct nfs_page *req)
+void nfs_free_request(struct nfs_page *req)
{
WARN_ON_ONCE(req->wb_this_page != req);
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 2e2b9f1..4dab432 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -46,6 +46,7 @@ static const struct rpc_call_ops nfs_commit_ops;
static const struct nfs_pgio_completion_ops nfs_async_write_completion_ops;
static const struct nfs_commit_completion_ops nfs_commit_completion_ops;
static const struct nfs_rw_ops nfs_rw_write_ops;
+static void nfs_clear_request_commit(struct nfs_page *req);
static struct kmem_cache *nfs_wdata_cachep;
static mempool_t *nfs_wdata_mempool;
@@ -289,36 +290,245 @@ static void nfs_end_page_writeback(struct nfs_page *req)
clear_bdi_congested(&nfss->backing_dev_info, BLK_RW_ASYNC);
}
-static struct nfs_page *nfs_find_and_lock_request(struct page *page, bool nonblock)
+
+/* nfs_page_group_clear_bits
+ * @req - an nfs request
+ * clears all page group related bits from @req
+ */
+static void
+nfs_page_group_clear_bits(struct nfs_page *req)
+{
+ clear_bit(PG_TEARDOWN, &req->wb_flags);
+ clear_bit(PG_UNLOCKPAGE, &req->wb_flags);
+ clear_bit(PG_UPTODATE, &req->wb_flags);
+ clear_bit(PG_WB_END, &req->wb_flags);
+ clear_bit(PG_REMOVE, &req->wb_flags);
+}
+
+
+/*
+ * nfs_unroll_locks_and_wait - unlock all newly locked reqs and wait on @req
+ *
+ * this is a helper function for nfs_lock_and_join_requests
+ *
+ * @inode - inode associated with request page group, must be holding inode lock
+ * @head - head request of page group, must be holding head lock
+ * @req - request that couldn't lock and needs to wait on the req bit lock
+ * @nonblock - if true, don't actually wait
+ *
+ * NOTE: this must be called holding page_group bit lock and inode spin lock
+ * and BOTH will be released before returning.
+ *
+ * returns 0 on success, < 0 on error.
+ */
+static int
+nfs_unroll_locks_and_wait(struct inode *inode, struct nfs_page *head,
+ struct nfs_page *req, bool nonblock)
+{
+ struct nfs_page *tmp;
+ int ret;
+
+ /* relinquish all the locks successfully grabbed this run */
+ for (tmp = head ; tmp != req; tmp = tmp->wb_this_page)
+ nfs_unlock_request(tmp);
+
+ WARN_ON_ONCE(test_bit(PG_TEARDOWN, &req->wb_flags));
+
+ /* grab a ref on the request that will be waited on */
+ kref_get(&req->wb_kref);
+
+ nfs_page_group_unlock(head);
+ spin_unlock(&inode->i_lock);
+
+ /* release ref from nfs_page_find_head_request_locked */
+ nfs_release_request(head);
+
+ if (!nonblock)
+ ret = nfs_wait_on_request(req);
+ else
+ ret = -EAGAIN;
+ nfs_release_request(req);
+
+ return ret;
+}
+
+/*
+ * nfs_destroy_unlinked_subrequests - destroy recently unlinked subrequests
+ *
+ * @destroy_list - request list (using wb_this_page) terminated by @old_head
+ * @old_head - the old head of the list
+ *
+ * All subrequests must be locked and removed from all lists, so at this point
+ * they are only "active" in this function, and possibly in nfs_wait_on_request
+ * with a reference held by some other context.
+ */
+static void
+nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list,
+ struct nfs_page *old_head)
+{
+ while (destroy_list) {
+ struct nfs_page *subreq = destroy_list;
+
+ destroy_list = (subreq->wb_this_page == old_head) ?
+ NULL : subreq->wb_this_page;
+
+ WARN_ON_ONCE(old_head != subreq->wb_head);
+
+ /* make sure old group is not used */
+ subreq->wb_head = subreq;
+ subreq->wb_this_page = subreq;
+
+ nfs_clear_request_commit(subreq);
+
+ /* subreq is now totally disconnected from page group or any
+ * write / commit lists. last chance to wake any waiters */
+ nfs_unlock_request(subreq);
+
+ if (!test_bit(PG_TEARDOWN, &subreq->wb_flags)) {
+ /* release ref on old head request */
+ nfs_release_request(old_head);
+
+ nfs_page_group_clear_bits(subreq);
+
+ /* release the PG_INODE_REF reference */
+ if (test_and_clear_bit(PG_INODE_REF, &subreq->wb_flags))
+ nfs_release_request(subreq);
+ else
+ WARN_ON_ONCE(1);
+ } else {
+ WARN_ON_ONCE(test_bit(PG_CLEAN, &subreq->wb_flags));
+ /* zombie requests have already released the last
+ * reference and were waiting on the rest of the
+ * group to complete. Since it's no longer part of a
+ * group, simply free the request */
+ nfs_page_group_clear_bits(subreq);
+ nfs_free_request(subreq);
+ }
+ }
+}
+
+/*
+ * 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
+ * @nonblock - if true, don't block waiting for request locks
+ *
+ * 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, bool nonblock)
{
struct inode *inode = page_file_mapping(page)->host;
- struct nfs_page *req;
+ struct nfs_page *head, *subreq;
+ struct nfs_page *destroy_list = NULL;
+ unsigned int total_bytes;
int ret;
+try_again:
+ total_bytes = 0;
+
+ WARN_ON_ONCE(destroy_list);
+
spin_lock(&inode->i_lock);
- for (;;) {
- req = nfs_page_find_head_request_locked(NFS_I(inode), page);
- if (req == NULL)
- break;
- if (nfs_lock_request(req))
- break;
- /* Note: If we hold the page lock, as is the case in nfs_writepage,
- * then the call to nfs_lock_request() will always
- * succeed provided that someone hasn't already marked the
- * request as dirty (in which case we don't care).
- */
+
+ /*
+ * 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_locked(NFS_I(inode), page);
+
+ if (!head) {
spin_unlock(&inode->i_lock);
- if (!nonblock)
- ret = nfs_wait_on_request(req);
- else
- ret = -EAGAIN;
- nfs_release_request(req);
- if (ret != 0)
+ return NULL;
+ }
+
+ /* lock each request in the page group */
+ nfs_page_group_lock(head);
+ subreq = head;
+ do {
+ /*
+ * Subrequests are always contiguous, non overlapping
+ * and in order. If not, it's a programming error.
+ */
+ WARN_ON_ONCE(subreq->wb_offset !=
+ (head->wb_offset + total_bytes));
+
+ /* keep track of how many bytes this group covers */
+ total_bytes += subreq->wb_bytes;
+
+ if (!nfs_lock_request(subreq)) {
+ /* releases page group bit lock and
+ * inode spin lock and all references */
+ ret = nfs_unroll_locks_and_wait(inode, head,
+ subreq, nonblock);
+
+ if (ret == 0)
+ goto try_again;
+
return ERR_PTR(ret);
- spin_lock(&inode->i_lock);
+ }
+
+ subreq = subreq->wb_this_page;
+ } while (subreq != head);
+
+ /* Now that all requests are locked, make sure they aren't on any list.
+ * Commit list removal accounting is done after locks are dropped */
+ subreq = head;
+ do {
+ nfs_list_remove_request(subreq);
+ subreq = subreq->wb_this_page;
+ } while (subreq != head);
+
+ /* unlink subrequests from head, destroy them later */
+ if (head->wb_this_page != head) {
+ /* destroy list will be terminated by head */
+ destroy_list = head->wb_this_page;
+ head->wb_this_page = head;
+
+ /* change head request to cover whole range that
+ * the former page group covered */
+ head->wb_bytes = total_bytes;
}
+
+ /*
+ * prepare head request to be added to new pgio descriptor
+ */
+ nfs_page_group_clear_bits(head);
+
+ /*
+ * some part of the group was still on the inode list - otherwise
+ * the group wouldn't be involved in async write.
+ * grab a reference for the head request, iff it needs one.
+ */
+ if (!test_and_set_bit(PG_INODE_REF, &head->wb_flags))
+ kref_get(&head->wb_kref);
+
+ nfs_page_group_unlock(head);
+
+ /* drop lock to clear_request_commit the head req and clean up
+ * requests on destroy list */
spin_unlock(&inode->i_lock);
- return req;
+
+ nfs_destroy_unlinked_subrequests(destroy_list, head);
+
+ /* clean up commit list state */
+ nfs_clear_request_commit(head);
+
+ /* still holds ref on head from nfs_page_find_head_request_locked
+ * and still has lock on head from lock loop */
+ return head;
}
/*
@@ -331,7 +541,7 @@ static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio,
struct nfs_page *req;
int ret = 0;
- req = nfs_find_and_lock_request(page, nonblock);
+ req = nfs_lock_and_join_requests(page, nonblock);
if (!req)
goto out;
ret = PTR_ERR(req);
--
1.8.5.2 (Apple Git-48)
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