[PATCH] avoid memory allocations in xfs_fs_vcmn_err

Christoph Hellwig
2008-12-17T17:27:38Z

xfs_fs_vcmn_err can be called under a spinlock, but does a sleeping memory
allocation to create buffer for it's internal sprintf. Fortunately it's
the only caller of icmn_err, so we can merge the two and have one single
static buffer and spinlock protecting it. While we're at it make sure
we proper __attribute__ format annotations so that the compiler can detect
mismatched format strings.

Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: xfs/fs/xfs/support/debug.c
===================================================================
--- xfs.orig/fs/xfs/support/debug.c 2008-12-17 14:59:49.000000000 +0100
+++ xfs/fs/xfs/support/debug.c 2008-12-17 15:10:13.000000000 +0100
@@ -18,6 +18,13 @@
#include <xfs.h>
#include "debug.h"

+/* xfs_mount.h drags a lot of crap in, sorry.. */
+#include "xfs_sb.h"
+#include "xfs_inum.h"
+#include "xfs_ag.h"
+#include "xfs_dmapi.h"
+#include "xfs_mount.h"
+
static char message[1024]; /* keep it off the stack */
static DEFINE_SPINLOCK(xfs_err_lock);

@@ -55,22 +62,42 @@ cmn_err(register int level, char *fmt, .
}

void
-icmn_err(register int level, char *fmt, va_list ap)
+xfs_fs_vcmn_err(
+ int level,
+ struct xfs_mount *mp,
+ char *fmt,
+ va_list ap)
{
- ulong flags;
- int len;
+ unsigned long flags;
+ int len = 0;

level &= XFS_ERR_MASK;
- if(level > XFS_MAX_ERR_LEVEL)
+ if (level > XFS_MAX_ERR_LEVEL)
level = XFS_MAX_ERR_LEVEL;
+
spin_lock_irqsave(&xfs_err_lock,flags);
- len = vsnprintf(message, sizeof(message), fmt, ap);
+
+ if (mp) {
+ len = sprintf(message, "Filesystem \"%s\": ", mp->m_fsname);
+
+ /*
+ * Skip the printk if we can't print anything useful
+ * due to an over-long device name.
+ */
+ if (len >= sizeof(message))
+ goto out;
+ }
+
+ len = vsnprintf(message + len, sizeof(message) - len, fmt, ap);
if (len >= sizeof(message))
len = sizeof(message) - 1;
if (message[len-1] == '\n')
message[len-1] = 0;
+
printk("%s%s\n", err_level[level], message);
+ out:
spin_unlock_irqrestore(&xfs_err_lock,flags);
+
BUG_ON(level == CE_PANIC);
}

Index: xfs/fs/xfs/support/debug.h
===================================================================
--- xfs.orig/fs/xfs/support/debug.h 2008-12-17 15:05:34.000000000 +0100
+++ xfs/fs/xfs/support/debug.h 2008-12-17 15:07:03.000000000 +0100
@@ -27,8 +27,6 @@
#define CE_ALERT 1 /* alert */
#define CE_PANIC 0 /* panic */

-extern void icmn_err(int, char *, va_list)
- __attribute__ ((format (printf, 2, 0)));
extern void cmn_err(int, char *, ...)
__attribute__ ((format (printf, 2, 3)));
extern void assfail(char *expr, char *f, int l);
Index: xfs/fs/xfs/xfs_error.c
===================================================================
--- xfs.orig/fs/xfs/xfs_error.c 2008-12-17 14:58:02.000000000 +0100
+++ xfs/fs/xfs/xfs_error.c 2008-12-17 15:12:03.000000000 +0100
@@ -153,21 +153,6 @@ xfs_errortag_clearall(xfs_mount_t *mp, i
}
#endif /* DEBUG */

-static void
-xfs_fs_vcmn_err(int level, xfs_mount_t *mp, char *fmt, va_list ap)
-{
- if (mp != NULL) {
- char *newfmt;
- int len = 16 + mp->m_fsname_len + strlen(fmt);
-
- newfmt = kmem_alloc(len, KM_SLEEP);
- sprintf(newfmt, "Filesystem \"%s\": %s", mp->m_fsname, fmt);
- icmn_err(level, newfmt, ap);
- kmem_free(newfmt);
- } else {
- icmn_err(level, fmt, ap);
- }
-}

void
xfs_fs_cmn_err(int level, xfs_mount_t *mp, char *fmt, ...)
Index: xfs/fs/xfs/xfs_error.h
===================================================================
--- xfs.orig/fs/xfs/xfs_error.h 2008-12-17 15:05:46.000000000 +0100
+++ xfs/fs/xfs/xfs_error.h 2008-12-17 15:12:01.000000000 +0100
@@ -159,11 +159,15 @@ extern int xfs_errortag_clearall(xfs_mou
#define XFS_PTAG_FSBLOCK_ZERO 0x00000080

struct xfs_mount;
-/* PRINTFLIKE4 */
+
+extern void xfs_fs_vcmn_err(int level, struct xfs_mount *mp,
+ char *fmt, va_list ap)
+ __attribute__ ((format (printf, 3, 0)));
extern void xfs_cmn_err(int panic_tag, int level, struct xfs_mount *mp,
- char *fmt, ...);
-/* PRINTFLIKE3 */
-extern void xfs_fs_cmn_err(int level, struct xfs_mount *mp, char *fmt, ...);
+ char *fmt, ...)
+ __attribute__ ((format (printf, 4, 5)));
+extern void xfs_fs_cmn_err(int level, struct xfs_mount *mp, char *fmt, ...)
+ __attribute__ ((format (printf, 3, 4)));

extern void xfs_hex_dump(void *p, int length);