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Subject: Re: [PATCH 3/5] pnfs: find swapped pages on pnfs commit lists too
From: Weston Andros Adamson <dros@primarydata.com>
In-Reply-To: <53E8C593.6030705@gmail.com>
Date: Mon, 11 Aug 2014 22:54:37 -0400
Cc: Trond Myklebust <trond.myklebust@primarydata.com>,
        linux-nfs list <linux-nfs@vger.kernel.org>
Message-Id: <583CC103-DC3D-495D-8C15-473BB8D2998D@primarydata.com>
References: <1407510816-7002-1-git-send-email-dros@primarydata.com> <1407510816-7002-4-git-send-email-dros@primarydata.com> <53E8C593.6030705@gmail.com>
To: Anna Schumaker <schumaker.anna@gmail.com>
Sender: linux-nfs-owner@vger.kernel.org

Thanks Anna, I?ll fix it up.

-dros


On Aug 11, 2014, at 9:30 AM, Anna Schumaker <schumaker.anna@gmail.com> wrote:

> On 08/08/2014 11:13 AM, Weston Andros Adamson wrote:
>> nfs_page_find_head_request_locked looks through the regular nfs commit lists
>> when the page is swapped out, but doesn't look through the pnfs commit lists.
>> 
>> I'm not sure if anyone has hit any issues caused by this.
>> 
>> Suggested-by: Peng Tao <tao.peng@primarydata.com>
>> Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
>> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
>> ---
>> fs/nfs/filelayout/filelayout.c | 31 ++++++++++++++++++++++++++
>> fs/nfs/pnfs.h                  | 20 +++++++++++++++++
>> fs/nfs/write.c                 | 49 +++++++++++++++++++++++++++++++-----------
>> 3 files changed, 88 insertions(+), 12 deletions(-)
>> 
>> diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c
>> index 2576d28b..524e66f 100644
>> --- a/fs/nfs/filelayout/filelayout.c
>> +++ b/fs/nfs/filelayout/filelayout.c
>> @@ -1237,6 +1237,36 @@ restart:
>> 	spin_unlock(cinfo->lock);
>> }
>> 
>> +/* filelayout_search_commit_reqs - Search lists in @cinfo for the head reqest
>> + *				   for @page
>> + * @cinfo - commit info for current inode
>> + * @page - page to search for matching head request
>> + *
>> + * Returns a the head request if one is found, otherwise returns NULL.
>> + */
>> +static struct nfs_page *
>> +filelayout_search_commit_reqs(struct nfs_commit_info *cinfo, struct page *page)
>> +{
>> +	struct nfs_page *freq, *t;
>> +	struct pnfs_commit_bucket *b;
>> +	int i;
>> +
>> +	/* Linearly search the commit lists for each bucket until a matching
>> +	 * request is found */
>> +	for (i = 0, b = cinfo->ds->buckets; i < cinfo->ds->nbuckets; i++, b++) {
>> +		list_for_each_entry_safe(freq, t, &b->written, wb_list) {
>> +			if (freq->wb_page == page)
>> +				return freq->wb_head;
>> +		}
>> +		list_for_each_entry_safe(freq, t, &b->committing, wb_list) {
>> +			if (freq->wb_page == page)
>> +				return freq->wb_head;
>> +		}
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> static void filelayout_retry_commit(struct nfs_commit_info *cinfo, int idx)
>> {
>> 	struct pnfs_ds_commit_info *fl_cinfo = cinfo->ds;
>> @@ -1386,6 +1416,7 @@ static struct pnfs_layoutdriver_type filelayout_type = {
>> 	.clear_request_commit	= filelayout_clear_request_commit,
>> 	.scan_commit_lists	= filelayout_scan_commit_lists,
>> 	.recover_commit_reqs	= filelayout_recover_commit_reqs,
>> +	.search_commit_reqs	= filelayout_search_commit_reqs,
>> 	.commit_pagelist	= filelayout_commit_pagelist,
>> 	.read_pagelist		= filelayout_read_pagelist,
>> 	.write_pagelist		= filelayout_write_pagelist,
>> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
>> index 27ddecd..203b6c9 100644
>> --- a/fs/nfs/pnfs.h
>> +++ b/fs/nfs/pnfs.h
>> @@ -104,6 +104,8 @@ struct pnfs_layoutdriver_type {
>> 				  int max);
>> 	void (*recover_commit_reqs) (struct list_head *list,
>> 				     struct nfs_commit_info *cinfo);
>> +	struct nfs_page * (*search_commit_reqs)(struct nfs_commit_info *cinfo,
>> +						struct page *page);
>> 	int (*commit_pagelist)(struct inode *inode,
>> 			       struct list_head *mds_pages,
>> 			       int how,
>> @@ -341,6 +343,17 @@ pnfs_recover_commit_reqs(struct inode *inode, struct list_head *list,
>> 	NFS_SERVER(inode)->pnfs_curr_ld->recover_commit_reqs(list, cinfo);
>> }
>> 
>> +static inline struct nfs_page *
>> +pnfs_search_commit_reqs(struct inode *inode, struct nfs_commit_info *cinfo,
>> +			struct page *page)
>> +{
>> +	struct pnfs_layoutdriver_type *ld = NFS_SERVER(inode)->pnfs_curr_ld;
>> +
>> +	if (ld == NULL || ld->search_commit_reqs == NULL)
>> +		return NULL;
>> +	return ld->search_commit_reqs(cinfo, page);
>> +}
>> +
>> /* Should the pNFS client commit and return the layout upon a setattr */
>> static inline bool
>> pnfs_ld_layoutret_on_setattr(struct inode *inode)
>> @@ -492,6 +505,13 @@ pnfs_recover_commit_reqs(struct inode *inode, struct list_head *list,
>> {
>> }
>> 
>> +static inline struct nfs_page *
>> +pnfs_search_commit_reqs(struct inode *inode, struct nfs_commit_info *cinfo,
>> +			struct page *page)
>> +{
>> +	return NULL;
>> +}
>> +
>> static inline int pnfs_layoutcommit_inode(struct inode *inode, bool sync)
>> {
>> 	return 0;
>> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
>> index e6bc5b5..ba41769 100644
>> --- a/fs/nfs/write.c
>> +++ b/fs/nfs/write.c
>> @@ -47,6 +47,8 @@ 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 void nfs_init_cinfo_from_inode(struct nfs_commit_info *cinfo,
>> +				      struct inode *inode);
>> 
>> static struct kmem_cache *nfs_wdata_cachep;
>> static mempool_t *nfs_wdata_mempool;
>> @@ -93,6 +95,38 @@ static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error)
>> }
>> 
>> /*
>> + * nfs_page_search_commits_for_head_request_locked
>> + *
>> + * Search through commit lists on @inode for the head request for @page.
>> + * Must be called while holding the inode (which is cinfo) lock.
>> + *
>> + * Returns the head request if found, or NULL if not found.
>> + */
>> +static struct nfs_page *
>> +nfs_page_search_commits_for_head_request_locked(struct nfs_inode *nfsi,
>> +						struct page *page)
>> +{
>> +	struct nfs_page *freq, *t;
>> +	struct nfs_commit_info cinfo;
>> +	struct inode *inode = &nfsi->vfs_inode;
>> +
>> +	nfs_init_cinfo_from_inode(&cinfo, inode);
> This has a compiler warning when CONFIG_NFS_V4=n, CONFIG_NFS_V3=n, CONFIG_NFS_V2=y:
> 
> fs/nfs/write.c: In function ?nfs_page_find_head_request_locked.isra.16?:
> include/linux/kernel.h:834:39: error: ?cinfo.mds? may be used uninitialized in this function [-Werror=maybe-uninitialized]
>  const typeof( ((type *)0)->member ) *__mptr = (ptr); \
>                                       ^
> fs/nfs/write.c:110:25: note: ?cinfo.mds? was declared here
>  struct nfs_commit_info cinfo;
> 
> Probably because nfs_init_cinfo_from_inode() is empty without v3 or v4.
> 
> Anna
>> +
>> +	/* search through pnfs commit lists */
>> +	freq = pnfs_search_commit_reqs(inode, &cinfo, page);
>> +	if (freq)
>> +		return freq->wb_head;
>> +
>> +	/* Linearly search the commit list for the correct request */
>> +	list_for_each_entry_safe(freq, t, &cinfo.mds->list, wb_list) {
>> +		if (freq->wb_page == page)
>> +			return freq->wb_head;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> +/*
>>  * nfs_page_find_head_request_locked - find head request associated with @page
>>  *
>>  * must be called while holding the inode lock.
>> @@ -106,21 +140,12 @@ nfs_page_find_head_request_locked(struct nfs_inode *nfsi, struct page *page)
>> 
>> 	if (PagePrivate(page))
>> 		req = (struct nfs_page *)page_private(page);
>> -	else if (unlikely(PageSwapCache(page))) {
>> -		struct nfs_page *freq, *t;
>> -
>> -		/* Linearly search the commit list for the correct req */
>> -		list_for_each_entry_safe(freq, t, &nfsi->commit_info.list, wb_list) {
>> -			if (freq->wb_page == page) {
>> -				req = freq->wb_head;
>> -				break;
>> -			}
>> -		}
>> -	}
>> +	else if (unlikely(PageSwapCache(page)))
>> +		req = nfs_page_search_commits_for_head_request_locked(nfsi,
>> +			page);
>> 
>> 	if (req) {
>> 		WARN_ON_ONCE(req->wb_head != req);
>> -
>> 		kref_get(&req->wb_kref);
>> 	}