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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>
hifive-unleashed-5.1
Akinobu Mita 2017-07-14 14:49:54 -07:00 committed by Linus Torvalds
parent 9049f2f6e7
commit bfc740938d
2 changed files with 13 additions and 14 deletions
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13
Documentation/fault-injection/fault-injection.txt
View File

@ -139,9 +139,9 @@ o proc entries
- /proc/self/task/<current-tid>/fail-nth: - /proc/self/task/<current-tid>/fail-nth:
Write to this file of integer N makes N-th call in the task fail. 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' Read from this file returns a integer value. A value of '0' indicates
that says if the fault setup with a previous write to this file was that the fault setup with a previous write to this file was injected.
injected or not, and disables the fault if it wasn't yet 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). Note that this file enables all types of faults (slab, futex, etc).
This setting takes precedence over all other generic debugfs settings This setting takes precedence over all other generic debugfs settings
like probability, interval, times, etc. But per-capability settings like probability, interval, times, etc. But per-capability settings
@ -325,13 +325,14 @@ int main()
write(fail_nth, buf, strlen(buf)); write(fail_nth, buf, strlen(buf));
res = socketpair(AF_LOCAL, SOCK_STREAM, 0, fds); res = socketpair(AF_LOCAL, SOCK_STREAM, 0, fds);
err = errno; err = errno;
read(fail_nth, buf, 1); pread(fail_nth, buf, sizeof(buf), 0);
if (res == 0) { if (res == 0) {
close(fds[0]); close(fds[0]);
close(fds[1]); close(fds[1]);
} }
printf("%d-th fault %c: res=%d/%d\n", i, buf[0], res, err); printf("%d-th fault %c: res=%d/%d\n", i, atoi(buf) ? 'N' : 'Y',
if (buf[0] != 'Y') res, err);
if (atoi(buf))
break; break;
} }
return 0; return 0;

14
fs/proc/base.c
View File

@ -1380,7 +1380,8 @@ static ssize_t proc_fail_nth_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos) size_t count, loff_t *ppos)
{ {
struct task_struct *task; struct task_struct *task;
int err; char numbuf[PROC_NUMBUF];
ssize_t len;
task = get_proc_task(file_inode(file)); task = get_proc_task(file_inode(file));
if (!task) if (!task)
@ -1388,13 +1389,10 @@ static ssize_t proc_fail_nth_read(struct file *file, char __user *buf,
put_task_struct(task); put_task_struct(task);
if (task != current) if (task != current)
return -EPERM; return -EPERM;
if (count < 1) len = snprintf(numbuf, sizeof(numbuf), "%u\n", task->fail_nth);
return -EINVAL; len = simple_read_from_buffer(buf, count, ppos, numbuf, len);
err = put_user((char)(current->fail_nth ? 'N' : 'Y'), buf);
if (err) return len;
return err;
current->fail_nth = 0;
return 1;
} }
static const struct file_operations proc_fail_nth_operations = { static const struct file_operations proc_fail_nth_operations = {