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    Subject[PATCH 4.2.y-ckt 128/268] cifs: Ratelimit kernel log messages
    Date
    4.2.8-ckt3 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

    From: Jamie Bainbridge <jamie.bainbridge@gmail.com>

    commit ec7147a99e33a9e4abad6fc6e1b40d15df045d53 upstream.

    Under some conditions, CIFS can repeatedly call the cifs_dbg() logging
    wrapper. If done rapidly enough, the console framebuffer can softlockup
    or "rcu_sched self-detected stall". Apply the built-in log ratelimiters
    to prevent such hangs.

    Signed-off-by: Jamie Bainbridge <jamie.bainbridge@gmail.com>
    Signed-off-by: Steve French <smfrench@gmail.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    fs/cifs/cifs_debug.c | 2 +-
    fs/cifs/cifs_debug.h | 9 ++++-----
    2 files changed, 5 insertions(+), 6 deletions(-)

    diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
    index 7febcf2..50b2684 100644
    --- a/fs/cifs/cifs_debug.c
    +++ b/fs/cifs/cifs_debug.c
    @@ -50,7 +50,7 @@ void cifs_vfs_err(const char *fmt, ...)
    vaf.fmt = fmt;
    vaf.va = &args;

    - pr_err("CIFS VFS: %pV", &vaf);
    + pr_err_ratelimited("CIFS VFS: %pV", &vaf);

    va_end(args);
    }
    diff --git a/fs/cifs/cifs_debug.h b/fs/cifs/cifs_debug.h
    index f40fbac..66cf0f9 100644
    --- a/fs/cifs/cifs_debug.h
    +++ b/fs/cifs/cifs_debug.h
    @@ -51,14 +51,13 @@ __printf(1, 2) void cifs_vfs_err(const char *fmt, ...);
    /* information message: e.g., configuration, major event */
    #define cifs_dbg(type, fmt, ...) \
    do { \
    - if (type == FYI) { \
    - if (cifsFYI & CIFS_INFO) { \
    - pr_debug("%s: " fmt, __FILE__, ##__VA_ARGS__); \
    - } \
    + if (type == FYI && cifsFYI & CIFS_INFO) { \
    + pr_debug_ratelimited("%s: " \
    + fmt, __FILE__, ##__VA_ARGS__); \
    } else if (type == VFS) { \
    cifs_vfs_err(fmt, ##__VA_ARGS__); \
    } else if (type == NOISY && type != 0) { \
    - pr_debug(fmt, ##__VA_ARGS__); \
    + pr_debug_ratelimited(fmt, ##__VA_ARGS__); \
    } \
    } while (0)

    --
    1.9.1
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