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	NFS: Wait for requests that are locked on the commit list
If a request is on the commit list, but is locked, we will currently skip it, which can lead to livelocking when the commit count doesn't reduce to zero. Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
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					 3 changed files with 29 additions and 8 deletions
				
			
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			@ -434,6 +434,7 @@ void nfs_release_request(struct nfs_page *req)
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{
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	kref_put(&req->wb_kref, nfs_page_group_destroy);
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}
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EXPORT_SYMBOL_GPL(nfs_release_request);
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/**
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 * nfs_wait_on_request - Wait for a request to complete.
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			@ -452,6 +453,7 @@ nfs_wait_on_request(struct nfs_page *req)
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	return wait_on_bit_io(&req->wb_flags, PG_BUSY,
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			      TASK_UNINTERRUPTIBLE);
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}
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EXPORT_SYMBOL_GPL(nfs_wait_on_request);
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/*
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 * nfs_generic_pg_test - determine if requests can be coalesced
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			@ -91,13 +91,23 @@ static int
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pnfs_generic_transfer_commit_list(struct list_head *src, struct list_head *dst,
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				  struct nfs_commit_info *cinfo, int max)
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{
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	struct nfs_page *req, *tmp;
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	struct nfs_page *req;
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	int ret = 0;
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	list_for_each_entry_safe(req, tmp, src, wb_list) {
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		if (!nfs_lock_request(req))
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			continue;
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	while(!list_empty(src)) {
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		req = list_first_entry(src, struct nfs_page, wb_list);
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		kref_get(&req->wb_kref);
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		if (!nfs_lock_request(req)) {
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			int status;
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			mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
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			status = nfs_wait_on_request(req);
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			nfs_release_request(req);
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			mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
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			if (status < 0)
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				break;
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			continue;
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		}
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		nfs_request_remove_commit_list(req, cinfo);
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		clear_bit(PG_COMMIT_TO_DS, &req->wb_flags);
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		nfs_list_add_request(req, dst);
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			@ -1030,13 +1030,22 @@ int
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nfs_scan_commit_list(struct list_head *src, struct list_head *dst,
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		     struct nfs_commit_info *cinfo, int max)
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{
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	struct nfs_page *req, *tmp;
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	struct nfs_page *req;
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	int ret = 0;
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	list_for_each_entry_safe(req, tmp, src, wb_list) {
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		if (!nfs_lock_request(req))
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			continue;
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	while(!list_empty(src)) {
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		req = list_first_entry(src, struct nfs_page, wb_list);
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		kref_get(&req->wb_kref);
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		if (!nfs_lock_request(req)) {
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			int status;
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			mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
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			status = nfs_wait_on_request(req);
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			nfs_release_request(req);
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			mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
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			if (status < 0)
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				break;
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			continue;
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		}
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		nfs_request_remove_commit_list(req, cinfo);
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		nfs_list_add_request(req, dst);
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		ret++;
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