linux-kernel - [PATCH] pstore: gracefully handle NULL pstore

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Date:	Thu, 17 Nov 2011 10:42:00 -0800
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Tony Luck <tony.luck@...el.com>, Matthew Garrett <mjg@...hat.com>,
	Chen Gong <gong.chen@...ux.intel.com>,
	Don Zickus <dzickus@...hat.com>, Arnd Bergmann <arnd@...db.de>
Subject: [PATCH] pstore: gracefully handle NULL pstore_info functions

If a pstore backend doesn't want to support various portions of the
pstore interface, it can just leave those functions NULL instead of
creating no-op stubs.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/pstore/inode.c    |    3 ++-
 fs/pstore/platform.c |   11 ++++++-----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 379a02d..b3b426e 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -80,7 +80,8 @@ static int pstore_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct pstore_private *p = dentry->d_inode->i_private;
 
-	p->psi->erase(p->type, p->id, p->psi);
+	if (p->psi->erase)
+		p->psi->erase(p->type, p->id, p->psi);
 
 	return simple_unlink(dir, dentry);
 }
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index f146d89..e12dfd7 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -178,7 +178,8 @@ int pstore_register(struct pstore_info *psi)
 	if (pstore_is_mounted())
 		pstore_get_records(0);
 
-	kmsg_dump_register(&pstore_dumper);
+	if (psi->write && psi->buf && psi->bufsize)
+		kmsg_dump_register(&pstore_dumper);
 
 	pstore_timer.expires = jiffies + PSTORE_INTERVAL;
 	add_timer(&pstore_timer);
@@ -203,12 +204,11 @@ void pstore_get_records(int quiet)
 	struct timespec		time;
 	int			failed = 0, rc;
 
-	if (!psi)
+	if (!psi || !psi->read)
 		return;
 
 	mutex_lock(&psi->read_mutex);
-	rc = psi->open(psi);
-	if (rc)
+	if (psi->open && psi->open(psi))
 		goto out;
 
 	while ((size = psi->read(&id, &type, &time, &buf, psi)) > 0) {
@@ -219,7 +219,8 @@ void pstore_get_records(int quiet)
 		if (rc && (rc != -EEXIST || !quiet))
 			failed++;
 	}
-	psi->close(psi);
+	if (psi->close)
+		psi->close(psi);
 out:
 	mutex_unlock(&psi->read_mutex);
 
-- 
1.7.0.4

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