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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: <583CC103-DC3D-495D-8C15-473BB8D2998D@primarydata.com>
Date: Fri, 15 Aug 2014 10:48:07 -0400
Cc: Trond Myklebust <trond.myklebust@primarydata.com>,
        linux-nfs list <linux-nfs@vger.kernel.org>
Message-Id: <54F24925-5237-4090-A4E4-EDA43F1DD2B8@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> <583CC103-DC3D-495D-8C15-473BB8D2998D@primarydata.com>
To: Anna Schumaker <schumaker.anna@gmail.com>
Sender: linux-nfs-owner@vger.kernel.org

For some reason I can?t reproduce this with:

CONFIG_NFS_FS=m
CONFIG_NFS_V2=m
# CONFIG_NFS_V3 is not set
# CONFIG_NFS_V4 is not set

Are you compiling with some special option? It?s not in the output of make W=1, W=3 or W=3.

It looks like there are several places that call nfs_init_cinfo_from_inode without any ifdef logic?

We could just fix all of them and be done with it, but I?m wondering why you get the warning and I don?t.

-dros


On Aug 11, 2014, at 10:54 PM, Weston Andros Adamson <dros@primarydata.com> wrote:

> 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);
>>> 	}
>