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Commit c4f24df9 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFS: Fix unstable write completion 



We do want to respect the FLUSH_SYNC argument to nfs_commit_inode() to
ensure that all outstanding COMMIT requests to the inode in question are
complete. Currently we may exit early from both nfs_commit_inode() and
nfs_write_inode() even if there are COMMIT requests in flight, or unstable
writes on the commit list.

In order to get the right semantics w.r.t. sync_inode(), we don't need
to have nfs_commit_inode() reset the inode dirty flags when called from
nfs_wb_page() and/or nfs_wb_all(). We just need to ensure that
nfs_write_inode() leaves them in the right state if there are outstanding
commits, or stable pages.

Reported-by: default avatarScott Mayhew <smayhew@redhat.com>
Fixes: dc4fd9ab ("nfs: don't wait on commit in nfs_commit_inode()...")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent 9c6376eb

fs/nfs/write.c

+43 −40
Original line number Diff line number Diff line
@@ -1876,40 +1876,43 @@ int nfs_generic_commit_list(struct inode *inode, struct list_head *head, 
	return status;

}



int nfs_commit_inode(struct inode *inode, int how)

static int __nfs_commit_inode(struct inode *inode, int how,

		struct writeback_control *wbc)

{

	LIST_HEAD(head);

	struct nfs_commit_info cinfo;

	int may_wait = how & FLUSH_SYNC;

	int error = 0;

	int res;

	int ret, nscan;



	nfs_init_cinfo_from_inode(&cinfo, inode);

	nfs_commit_begin(cinfo.mds);

	res = nfs_scan_commit(inode, &head, &cinfo);

	if (res)

		error = nfs_generic_commit_list(inode, &head, how, &cinfo);

	for (;;) {

		ret = nscan = nfs_scan_commit(inode, &head, &cinfo);

		if (ret <= 0)

			break;

		ret = nfs_generic_commit_list(inode, &head, how, &cinfo);

		if (ret < 0)

			break;

		ret = 0;

		if (wbc && wbc->sync_mode == WB_SYNC_NONE) {

			if (nscan < wbc->nr_to_write)

				wbc->nr_to_write -= nscan;

			else

				wbc->nr_to_write = 0;

		}

		if (nscan < INT_MAX)

			break;

		cond_resched();

	}

	nfs_commit_end(cinfo.mds);

	if (res == 0)

		return res;

	if (error < 0)

		goto out_error;

	if (!may_wait)

		goto out_mark_dirty;

	error = wait_on_commit(cinfo.mds);

	if (error < 0)

		return error;

	return res;

out_error:

	res = error;

	/* Note: If we exit without ensuring that the commit is complete,

	 * we must mark the inode as dirty. Otherwise, future calls to

	 * sync_inode() with the WB_SYNC_ALL flag set will fail to ensure

	 * that the data is on the disk.

	 */

out_mark_dirty:

	__mark_inode_dirty(inode, I_DIRTY_DATASYNC);

	return res;

	if (ret || !may_wait)

		return ret;

	return wait_on_commit(cinfo.mds);

}



int nfs_commit_inode(struct inode *inode, int how)

{

	return __nfs_commit_inode(inode, how, NULL);

}

EXPORT_SYMBOL_GPL(nfs_commit_inode);
@@ -1919,11 +1922,11 @@ int nfs_write_inode(struct inode *inode, struct writeback_control *wbc) 
	int flags = FLUSH_SYNC;

	int ret = 0;



	if (wbc->sync_mode == WB_SYNC_NONE) {

		/* no commits means nothing needs to be done */

		if (!atomic_long_read(&nfsi->commit_info.ncommit))

		return ret;

			goto check_requests_outstanding;



	if (wbc->sync_mode == WB_SYNC_NONE) {

		/* Don't commit yet if this is a non-blocking flush and there

		 * are a lot of outstanding writes for this mapping.

		 */
@@ -1934,16 +1937,16 @@ int nfs_write_inode(struct inode *inode, struct writeback_control *wbc) 
		flags = 0;

	}



	ret = nfs_commit_inode(inode, flags);

	if (ret >= 0) {

		if (wbc->sync_mode == WB_SYNC_NONE) {

			if (ret < wbc->nr_to_write)

				wbc->nr_to_write -= ret;

			else

				wbc->nr_to_write = 0;

		}

	ret = __nfs_commit_inode(inode, flags, wbc);

	if (!ret) {

		if (flags & FLUSH_SYNC)

			return 0;

	}

	} else if (atomic_long_read(&nfsi->commit_info.ncommit))

		goto out_mark_dirty;



check_requests_outstanding:

	if (!atomic_read(&nfsi->commit_info.rpcs_out))

		return ret;

out_mark_dirty:

	__mark_inode_dirty(inode, I_DIRTY_DATASYNC);

	return ret;