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    Subject[PATCH 4.4 09/35] include/trace/events/writeback.h: fix -Wstringop-truncation warnings
    Date
    From: Qian Cai <cai@lca.pw>

    [ Upstream commit d1a445d3b86c9341ce7a0954c23be0edb5c9bec5 ]

    There are many of those warnings.

    In file included from ./arch/powerpc/include/asm/paca.h:15,
    from ./arch/powerpc/include/asm/current.h:13,
    from ./include/linux/thread_info.h:21,
    from ./include/asm-generic/preempt.h:5,
    from ./arch/powerpc/include/generated/asm/preempt.h:1,
    from ./include/linux/preempt.h:78,
    from ./include/linux/spinlock.h:51,
    from fs/fs-writeback.c:19:
    In function 'strncpy',
    inlined from 'perf_trace_writeback_page_template' at
    ./include/trace/events/writeback.h:56:1:
    ./include/linux/string.h:260:9: warning: '__builtin_strncpy' specified
    bound 32 equals destination size [-Wstringop-truncation]
    return __builtin_strncpy(p, q, size);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Fix it by using the new strscpy_pad() which was introduced in "lib/string:
    Add strscpy_pad() function" and will always be NUL-terminated instead of
    strncpy(). Also, change strlcpy() to use strscpy_pad() in this file for
    consistency.

    Link: http://lkml.kernel.org/r/1564075099-27750-1-git-send-email-cai@lca.pw
    Fixes: 455b2864686d ("writeback: Initial tracing support")
    Fixes: 028c2dd184c0 ("writeback: Add tracing to balance_dirty_pages")
    Fixes: e84d0a4f8e39 ("writeback: trace event writeback_queue_io")
    Fixes: b48c104d2211 ("writeback: trace event bdi_dirty_ratelimit")
    Fixes: cc1676d917f3 ("writeback: Move requeueing when I_SYNC set to writeback_sb_inodes()")
    Fixes: 9fb0a7da0c52 ("writeback: add more tracepoints")
    Signed-off-by: Qian Cai <cai@lca.pw>
    Reviewed-by: Jan Kara <jack@suse.cz>
    Cc: Tobin C. Harding <tobin@kernel.org>
    Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Dave Chinner <dchinner@redhat.com>
    Cc: Fengguang Wu <fengguang.wu@intel.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Joe Perches <joe@perches.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Jann Horn <jannh@google.com>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Cc: Nitin Gote <nitin.r.gote@intel.com>
    Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
    Cc: Stephen Kitt <steve@sk2.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/trace/events/writeback.h | 38 +++++++++++++++++---------------
    1 file changed, 20 insertions(+), 18 deletions(-)

    diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
    index 2609b1c3549e2..07a912af1dd74 100644
    --- a/include/trace/events/writeback.h
    +++ b/include/trace/events/writeback.h
    @@ -65,8 +65,9 @@ TRACE_EVENT(writeback_dirty_page,
    ),

    TP_fast_assign(
    - strncpy(__entry->name,
    - mapping ? dev_name(inode_to_bdi(mapping->host)->dev) : "(unknown)", 32);
    + strscpy_pad(__entry->name,
    + mapping ? dev_name(inode_to_bdi(mapping->host)->dev) : "(unknown)",
    + 32);
    __entry->ino = mapping ? mapping->host->i_ino : 0;
    __entry->index = page->index;
    ),
    @@ -95,8 +96,8 @@ DECLARE_EVENT_CLASS(writeback_dirty_inode_template,
    struct backing_dev_info *bdi = inode_to_bdi(inode);

    /* may be called for files on pseudo FSes w/ unregistered bdi */
    - strncpy(__entry->name,
    - bdi->dev ? dev_name(bdi->dev) : "(unknown)", 32);
    + strscpy_pad(__entry->name,
    + bdi->dev ? dev_name(bdi->dev) : "(unknown)", 32);
    __entry->ino = inode->i_ino;
    __entry->state = inode->i_state;
    __entry->flags = flags;
    @@ -205,8 +206,8 @@ DECLARE_EVENT_CLASS(writeback_write_inode_template,
    ),

    TP_fast_assign(
    - strncpy(__entry->name,
    - dev_name(inode_to_bdi(inode)->dev), 32);
    + strscpy_pad(__entry->name,
    + dev_name(inode_to_bdi(inode)->dev), 32);
    __entry->ino = inode->i_ino;
    __entry->sync_mode = wbc->sync_mode;
    __trace_wbc_assign_cgroup(__get_str(cgroup), wbc);
    @@ -249,8 +250,9 @@ DECLARE_EVENT_CLASS(writeback_work_class,
    __dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
    ),
    TP_fast_assign(
    - strncpy(__entry->name,
    - wb->bdi->dev ? dev_name(wb->bdi->dev) : "(unknown)", 32);
    + strscpy_pad(__entry->name,
    + wb->bdi->dev ? dev_name(wb->bdi->dev) :
    + "(unknown)", 32);
    __entry->nr_pages = work->nr_pages;
    __entry->sb_dev = work->sb ? work->sb->s_dev : 0;
    __entry->sync_mode = work->sync_mode;
    @@ -303,7 +305,7 @@ DECLARE_EVENT_CLASS(writeback_class,
    __dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
    ),
    TP_fast_assign(
    - strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
    + strscpy_pad(__entry->name, dev_name(wb->bdi->dev), 32);
    __trace_wb_assign_cgroup(__get_str(cgroup), wb);
    ),
    TP_printk("bdi %s: cgroup=%s",
    @@ -326,7 +328,7 @@ TRACE_EVENT(writeback_bdi_register,
    __array(char, name, 32)
    ),
    TP_fast_assign(
    - strncpy(__entry->name, dev_name(bdi->dev), 32);
    + strscpy_pad(__entry->name, dev_name(bdi->dev), 32);
    ),
    TP_printk("bdi %s",
    __entry->name
    @@ -351,7 +353,7 @@ DECLARE_EVENT_CLASS(wbc_class,
    ),

    TP_fast_assign(
    - strncpy(__entry->name, dev_name(bdi->dev), 32);
    + strscpy_pad(__entry->name, dev_name(bdi->dev), 32);
    __entry->nr_to_write = wbc->nr_to_write;
    __entry->pages_skipped = wbc->pages_skipped;
    __entry->sync_mode = wbc->sync_mode;
    @@ -402,7 +404,7 @@ TRACE_EVENT(writeback_queue_io,
    __dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
    ),
    TP_fast_assign(
    - strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
    + strncpy_pad(__entry->name, dev_name(wb->bdi->dev), 32);
    __entry->older = dirtied_before;
    __entry->age = (jiffies - dirtied_before) * 1000 / HZ;
    __entry->moved = moved;
    @@ -487,7 +489,7 @@ TRACE_EVENT(bdi_dirty_ratelimit,
    ),

    TP_fast_assign(
    - strlcpy(__entry->bdi, dev_name(wb->bdi->dev), 32);
    + strscpy_pad(__entry->bdi, dev_name(wb->bdi->dev), 32);
    __entry->write_bw = KBps(wb->write_bandwidth);
    __entry->avg_write_bw = KBps(wb->avg_write_bandwidth);
    __entry->dirty_rate = KBps(dirty_rate);
    @@ -552,7 +554,7 @@ TRACE_EVENT(balance_dirty_pages,

    TP_fast_assign(
    unsigned long freerun = (thresh + bg_thresh) / 2;
    - strlcpy(__entry->bdi, dev_name(wb->bdi->dev), 32);
    + strscpy_pad(__entry->bdi, dev_name(wb->bdi->dev), 32);

    __entry->limit = global_wb_domain.dirty_limit;
    __entry->setpoint = (global_wb_domain.dirty_limit +
    @@ -613,8 +615,8 @@ TRACE_EVENT(writeback_sb_inodes_requeue,
    ),

    TP_fast_assign(
    - strncpy(__entry->name,
    - dev_name(inode_to_bdi(inode)->dev), 32);
    + strscpy_pad(__entry->name,
    + dev_name(inode_to_bdi(inode)->dev), 32);
    __entry->ino = inode->i_ino;
    __entry->state = inode->i_state;
    __entry->dirtied_when = inode->dirtied_when;
    @@ -687,8 +689,8 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
    ),

    TP_fast_assign(
    - strncpy(__entry->name,
    - dev_name(inode_to_bdi(inode)->dev), 32);
    + strscpy_pad(__entry->name,
    + dev_name(inode_to_bdi(inode)->dev), 32);
    __entry->ino = inode->i_ino;
    __entry->state = inode->i_state;
    __entry->dirtied_when = inode->dirtied_when;
    --
    2.27.0


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