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Subject[PATCH 2/2] tracing: Do not copy hash if O_TRUNC is set
Date
When a filter file is open for writing and O_TRUNC is set, there's no
need to copy and free the filter entries.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
kernel/trace/ftrace.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ddfda763ded7..13885590a184 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2759,7 +2759,13 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
hash = ops->filter_hash;

if (file->f_mode & FMODE_WRITE) {
- iter->hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);
+ const int size_bits = FTRACE_HASH_DEFAULT_BITS;
+
+ if (file->f_flags & O_TRUNC)
+ iter->hash = alloc_ftrace_hash(size_bits);
+ else
+ iter->hash = alloc_and_copy_ftrace_hash(size_bits, hash);
+
if (!iter->hash) {
trace_parser_put(&iter->parser);
kfree(iter);
@@ -2768,10 +2774,6 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
}
}

- if ((file->f_mode & FMODE_WRITE) &&
- (file->f_flags & O_TRUNC))
- ftrace_filter_reset(iter->hash);
-
if (file->f_mode & FMODE_READ) {
iter->pg = ftrace_pages_start;

--
2.0.0


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