diff options
authorAkinobu Mita <akinobu.mita@gmail.com>2017-07-14 14:49:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-14 15:05:13 -0700
commitbfc740938d151001cb1158580796f8f3be3bf0c1 (patch)
parent9049f2f6e7bdfb5de0c63c2635bf3cdb70c4efb5 (diff)
fault-inject: make fail-nth read/write interface symmetric
The read interface for fail-nth looks a bit odd. Read from this file returns "NYYYY..." or "YYYYY..." (this makes me surprise when cat this file). Because there is no EOF condition. The first character indicates current->fail_nth is zero or not, and then current->fail_nth is reset to zero. Just returning task->fail_nth value is more natural to understand. Link: http://lkml.kernel.org/r/1491490561-10485-4-git-send-email-akinobu.mita@gmail.com Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2 files changed, 13 insertions, 14 deletions
diff --git a/Documentation/fault-injection/fault-injection.txt b/Documentation/fault-injection/fault-injection.txt
index a32190508751..370ddcbc2b44 100644
--- a/Documentation/fault-injection/fault-injection.txt
+++ b/Documentation/fault-injection/fault-injection.txt
@@ -139,9 +139,9 @@ o proc entries
- /proc/self/task/<current-tid>/fail-nth:
Write to this file of integer N makes N-th call in the task fail.
- Read from this file returns a single char 'Y' or 'N'
- that says if the fault setup with a previous write to this file was
- injected or not, and disables the fault if it wasn't yet injected.
+ Read from this file returns a integer value. A value of '0' indicates
+ that the fault setup with a previous write to this file was injected.
+ A positive integer N indicates that the fault wasn't yet injected.
Note that this file enables all types of faults (slab, futex, etc).
This setting takes precedence over all other generic debugfs settings
like probability, interval, times, etc. But per-capability settings
@@ -325,13 +325,14 @@ int main()
write(fail_nth, buf, strlen(buf));
res = socketpair(AF_LOCAL, SOCK_STREAM, 0, fds);
err = errno;
- read(fail_nth, buf, 1);
+ pread(fail_nth, buf, sizeof(buf), 0);
if (res == 0) {
- printf("%d-th fault %c: res=%d/%d\n", i, buf[0], res, err);
- if (buf[0] != 'Y')
+ printf("%d-th fault %c: res=%d/%d\n", i, atoi(buf) ? 'N' : 'Y',
+ res, err);
+ if (atoi(buf))
return 0;
diff --git a/fs/proc/base.c b/fs/proc/base.c
index c1fdaecb8d23..7d795d28dd02 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1380,7 +1380,8 @@ static ssize_t proc_fail_nth_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
struct task_struct *task;
- int err;
+ char numbuf[PROC_NUMBUF];
+ ssize_t len;
task = get_proc_task(file_inode(file));
if (!task)
@@ -1388,13 +1389,10 @@ static ssize_t proc_fail_nth_read(struct file *file, char __user *buf,
if (task != current)
return -EPERM;
- if (count < 1)
- return -EINVAL;
- err = put_user((char)(current->fail_nth ? 'N' : 'Y'), buf);
- if (err)
- return err;
- current->fail_nth = 0;
- return 1;
+ len = snprintf(numbuf, sizeof(numbuf), "%u\n", task->fail_nth);
+ len = simple_read_from_buffer(buf, count, ppos, numbuf, len);
+ return len;
static const struct file_operations proc_fail_nth_operations = {

Privacy Policy