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Re: [PATCH] avoid memory allocations in xfs_fs_vcmn_err

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH] avoid memory allocations in xfs_fs_vcmn_err
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Wed, 17 Dec 2008 12:04:40 -0600
Cc: xfs@xxxxxxxxxxx, Alexander Beregalov <a.beregalov@xxxxxxxxx>
In-reply-to: <20081217172736.GA10797@xxxxxxxxxxxxx>
References: <20081217172736.GA10797@xxxxxxxxxxxxx>
User-agent: Thunderbird 2.0.0.18 (Macintosh/20081105)
Christoph Hellwig wrote:
> 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@xxxxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxxx>

> 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);
>  
> 
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