nfs: nfs_page should take a ref on the head req
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>
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@ -239,15 +239,21 @@ nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
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WARN_ON_ONCE(prev == req);
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if (!prev) {
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/* a head request */
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req->wb_head = req;
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req->wb_this_page = req;
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} else {
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/* a subrequest */
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WARN_ON_ONCE(prev->wb_this_page != prev->wb_head);
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WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &prev->wb_head->wb_flags));
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req->wb_head = prev->wb_head;
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req->wb_this_page = prev->wb_this_page;
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prev->wb_this_page = req;
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/* All subrequests take a ref on the head request until
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* nfs_page_group_destroy is called */
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kref_get(&req->wb_head->wb_kref);
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/* grab extra ref if head request has extra ref from
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* the write/commit path to handle handoff between write
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* and commit lists */
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@ -271,6 +277,10 @@ nfs_page_group_destroy(struct kref *kref)
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struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
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struct nfs_page *tmp, *next;
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/* subrequests must release the ref on the head request */
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if (req->wb_head != req)
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nfs_release_request(req->wb_head);
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if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
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return;
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