pNFS: Fix potential corruption of page being written

Kazuo Ito · Trond Myklebust · commit 97ae91bbf3a7 · 2019-02-20T17:33:55.000-05:00
nfs_want_read_modify_write() didn't check for !PagePrivate when pNFS
block or SCSI layout was in use, therefore we could lose data forever
if the page being written was filled by a read before completion.

Signed-off-by: Kazuo Ito &lt;ito_kazuo_g3@lab.ntt.co.jp&gt;
Signed-off-by: Trond Myklebust &lt;trond.myklebust@hammerspace.com&gt;
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
@@ -299,7 +299,7 @@ static int nfs_want_read_modify_write(struct file *file, struct page *page,
 	unsigned int end = offset + len;
 
 	if (pnfs_ld_read_whole_page(file->f_mapping->host)) {
-		if (!PageUptodate(page))
+		if (!PageUptodate(page) && !PagePrivate(page))
 			return 1;
 		return 0;
 	}

Original file line number	Diff line number	Diff line change
`@@ -299,7 +299,7 @@ static int nfs_want_read_modify_write(struct file file, struct page page,`
`299`	`299`	`unsigned int end = offset + len;`
`300`	`300`
`301`	`301`	`if (pnfs_ld_read_whole_page(file->f_mapping->host)) {`
`302`		`- if (!PageUptodate(page))`
	`302`	`+ if (!PageUptodate(page) && !PagePrivate(page))`
`303`	`303`	`return 1;`
`304`	`304`	`return 0;`
`305`	`305`	`}`