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Commit cb1410c7 authored by Weston Andros Adamson's avatar Weston Andros Adamson Committed by Trond Myklebust
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NFS: fix subtle change in COMMIT behavior 



Recent work in the pgio layer made it possible for there to be more than one
request per page. This caused a subtle change in commit behavior, because
write.c:nfs_commit_unstable_pages compares the number of *pages* waiting for
writeback against the number of requests on a commit list to choose when to
send a COMMIT in a non-blocking flush.

This is probably hard to hit in normal operation - you have to be using
rsize/wsize < PAGE_SIZE, or pnfs with lots of boundaries that are not page
aligned to have a noticeable change in behavior.

Signed-off-by: default avatarWeston Andros Adamson <dros@primarydata.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent 6a74c0c9

fs/nfs/callback_proc.c

+1 −1
Original line number Diff line number Diff line
@@ -49,7 +49,7 @@ __be32 nfs4_callback_getattr(struct cb_getattrargs *args, 
		goto out_iput;

	res->size = i_size_read(inode);

	res->change_attr = delegation->change_attr;

	if (nfsi->npages != 0)

	if (nfsi->nrequests != 0)

		res->change_attr++;

	res->ctime = inode->i_ctime;

	res->mtime = inode->i_mtime;

fs/nfs/inode.c

+4 −4
Original line number Diff line number Diff line
@@ -1149,7 +1149,7 @@ static unsigned long nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr 
	if ((fattr->valid & NFS_ATTR_FATTR_PRESIZE)

			&& (fattr->valid & NFS_ATTR_FATTR_SIZE)

			&& i_size_read(inode) == nfs_size_to_loff_t(fattr->pre_size)

			&& nfsi->npages == 0) {

			&& nfsi->nrequests == 0) {

		i_size_write(inode, nfs_size_to_loff_t(fattr->size));

		ret |= NFS_INO_INVALID_ATTR;

	}
@@ -1192,7 +1192,7 @@ static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fat 
	if (fattr->valid & NFS_ATTR_FATTR_SIZE) {

		cur_size = i_size_read(inode);

		new_isize = nfs_size_to_loff_t(fattr->size);

		if (cur_size != new_isize && nfsi->npages == 0)

		if (cur_size != new_isize && nfsi->nrequests == 0)

			invalid |= NFS_INO_INVALID_ATTR|NFS_INO_REVAL_PAGECACHE;

	}
@@ -1619,7 +1619,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr) 
		if (new_isize != cur_isize) {

			/* Do we perhaps have any outstanding writes, or has

			 * the file grown beyond our last write? */

			if ((nfsi->npages == 0) || new_isize > cur_isize) {

			if ((nfsi->nrequests == 0) || new_isize > cur_isize) {

				i_size_write(inode, new_isize);

				invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;

				invalid &= ~NFS_INO_REVAL_PAGECACHE;
@@ -1784,7 +1784,7 @@ static void init_once(void *foo) 
	INIT_LIST_HEAD(&nfsi->access_cache_entry_lru);

	INIT_LIST_HEAD(&nfsi->access_cache_inode_lru);

	INIT_LIST_HEAD(&nfsi->commit_info.list);

	nfsi->npages = 0;

	nfsi->nrequests = 0;

	nfsi->commit_info.ncommit = 0;

	atomic_set(&nfsi->commit_info.rpcs_out, 0);

	atomic_set(&nfsi->silly_count, 1);

fs/nfs/pagelist.c

+8 −3
Original line number Diff line number Diff line
@@ -258,6 +258,7 @@ bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit) 
static inline void

nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)

{

	struct inode *inode;

	WARN_ON_ONCE(prev == req);



	if (!prev) {
@@ -276,12 +277,16 @@ nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev) 
		 * 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 */

		/* grab extra ref and bump the request count if head request

		 * has extra ref from the write/commit path to handle handoff

		 * between write and commit lists. */

		if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags)) {

			inode = page_file_mapping(req->wb_page)->host;

			set_bit(PG_INODE_REF, &req->wb_flags);

			kref_get(&req->wb_kref);

			spin_lock(&inode->i_lock);

			NFS_I(inode)->nrequests++;

			spin_unlock(&inode->i_lock);

		}

	}

}

fs/nfs/write.c

+12 −5
Original line number Diff line number Diff line
@@ -670,7 +670,8 @@ static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req) 
	nfs_lock_request(req);



	spin_lock(&inode->i_lock);

	if (!nfsi->npages && NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))

	if (!nfsi->nrequests &&

	    NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))

		inode->i_version++;

	/*

	 * Swap-space should not get truncated. Hence no need to plug the race
@@ -681,9 +682,11 @@ static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req) 
		SetPagePrivate(req->wb_page);

		set_page_private(req->wb_page, (unsigned long)req);

	}

	nfsi->npages++;

	nfsi->nrequests++;

	/* this a head request for a page group - mark it as having an

	 * extra reference so sub groups can follow suit */

	 * extra reference so sub groups can follow suit.

	 * This flag also informs pgio layer when to bump nrequests when

	 * adding subrequests. */

	WARN_ON(test_and_set_bit(PG_INODE_REF, &req->wb_flags));

	kref_get(&req->wb_kref);

	spin_unlock(&inode->i_lock);
@@ -709,7 +712,11 @@ static void nfs_inode_remove_request(struct nfs_page *req) 
			wake_up_page(head->wb_page, PG_private);

			clear_bit(PG_MAPPED, &head->wb_flags);

		}

		nfsi->npages--;

		nfsi->nrequests--;

		spin_unlock(&inode->i_lock);

	} else {

		spin_lock(&inode->i_lock);

		nfsi->nrequests--;

		spin_unlock(&inode->i_lock);

	}
@@ -1735,7 +1742,7 @@ static int nfs_commit_unstable_pages(struct inode *inode, struct writeback_contr 
		/* Don't commit yet if this is a non-blocking flush and there

		 * are a lot of outstanding writes for this mapping.

		 */

		if (nfsi->commit_info.ncommit <= (nfsi->npages >> 1))

		if (nfsi->commit_info.ncommit <= (nfsi->nrequests >> 1))

			goto out_mark_dirty;



		/* don't wait for the COMMIT response */

include/linux/nfs_fs.h

+2 −2
Original line number Diff line number Diff line
@@ -163,7 +163,7 @@ struct nfs_inode { 
	 */

	__be32			cookieverf[2];



	unsigned long		npages;

	unsigned long		nrequests;

	struct nfs_mds_commit_info commit_info;



	/* Open contexts for shared mmap writes */
@@ -520,7 +520,7 @@ extern void nfs_commit_free(struct nfs_commit_data *data); 
static inline int

nfs_have_writebacks(struct inode *inode)

{

	return NFS_I(inode)->npages != 0;

	return NFS_I(inode)->nrequests != 0;

}



/*