[PATCH] trace/writeback: fix Wstringop-truncation warnings

[Qian Cai]

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 strlcpy() which will always be NUL-terminated instead of
strncpy(). strlcpy() has already been used at some places in this file.

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@xxxxxx>
---
 include/trace/events/writeback.h | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index aa7f3aeac740..8e3b3c4fd964 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -66,7 +66,7 @@
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->name,
+		strlcpy(__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;
@@ -110,7 +110,7 @@
 		struct backing_dev_info *bdi = inode_to_bdi(inode);
 
 		/* may be called for files on pseudo FSes w/ unregistered bdi */
-		strncpy(__entry->name,
+		strlcpy(__entry->name,
 			bdi->dev ? dev_name(bdi->dev) : "(unknown)", 32);
 		__entry->ino		= inode->i_ino;
 		__entry->state		= inode->i_state;
@@ -190,7 +190,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->name,
+		strlcpy(__entry->name,
 			dev_name(inode_to_bdi(inode)->dev), 32);
 		__entry->ino		= inode->i_ino;
 		__entry->sync_mode	= wbc->sync_mode;
@@ -234,7 +234,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 		__field(unsigned int, cgroup_ino)
 	),
 	TP_fast_assign(
-		strncpy(__entry->name,
+		strlcpy(__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;
@@ -288,7 +288,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 		__field(unsigned int, cgroup_ino)
 	),
 	TP_fast_assign(
-		strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
+		strlcpy(__entry->name, dev_name(wb->bdi->dev), 32);
 		__entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
 	),
 	TP_printk("bdi %s: cgroup_ino=%u",
@@ -310,7 +310,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 		__array(char, name, 32)
 	),
 	TP_fast_assign(
-		strncpy(__entry->name, dev_name(bdi->dev), 32);
+		strlcpy(__entry->name, dev_name(bdi->dev), 32);
 	),
 	TP_printk("bdi %s",
 		__entry->name
@@ -335,7 +335,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->name, dev_name(bdi->dev), 32);
+		strlcpy(__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;
@@ -386,7 +386,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 	),
 	TP_fast_assign(
 		unsigned long *older_than_this = work->older_than_this;
-		strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
+		strlcpy(__entry->name, dev_name(wb->bdi->dev), 32);
 		__entry->older	= older_than_this ?  *older_than_this : 0;
 		__entry->age	= older_than_this ?
 				  (jiffies - *older_than_this) * 1000 / HZ : -1;
@@ -597,7 +597,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->name,
+		strlcpy(__entry->name,
 		        dev_name(inode_to_bdi(inode)->dev), 32);
 		__entry->ino		= inode->i_ino;
 		__entry->state		= inode->i_state;
@@ -671,7 +671,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->name,
+		strlcpy(__entry->name,
 			dev_name(inode_to_bdi(inode)->dev), 32);
 		__entry->ino		= inode->i_ino;
 		__entry->state		= inode->i_state;
-- 
1.8.3.1