nfs_pages that aren't the the head of a group must take a reference on the
head as long as ->wb_head is set to it. This stops the head from hitting
a refcount of 0 while there is still an active nfs_page for the page group.
This avoids kref warnings in the writeback code when the page group head
is found and referenced.
Signed-off-by: Weston Andros Adamson <dros@xxxxxxxxxxxxxxx>
---
fs/nfs/pagelist.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 50e10bb..8b074da 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -239,15 +239,21 @@ nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
WARN_ON_ONCE(prev == req);
if (!prev) {
+ /* a head request */
req->wb_head = req;
req->wb_this_page = req;
} else {
+ /* a subrequest */
WARN_ON_ONCE(prev->wb_this_page != prev->wb_head);
WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &prev->wb_head->wb_flags));
req->wb_head = prev->wb_head;
req->wb_this_page = prev->wb_this_page;
prev->wb_this_page = req;
+ /* All subrequests take a ref on the head request until
+ * nfs_page_group_destroy is called */
+ kref_get(&req->wb_head->wb_kref);
+
/* grab extra ref if head request has extra ref from
* the write/commit path to handle handoff between write
* and commit lists */
@@ -271,6 +277,10 @@ nfs_page_group_destroy(struct kref *kref)
struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
struct nfs_page *tmp, *next;
+ /* subrequests must release the ref on the head request */
+ if (req->wb_head != req)
+ nfs_release_request(req->wb_head);
+
if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
return;
--
1.8.5.2 (Apple Git-48)
--
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