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nfs: nfs_page should take a ref on the head req

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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@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Weston Andros Adamson 2014-07-11 10:20:46 -04:00 committed by Trond Myklebust
parent 17089a29a2
commit 85710a837c
1 changed files with 10 additions and 0 deletions
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10
fs/nfs/pagelist.c
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@ -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;