Re: dio_get_page() lockdep complaints

[Jens Axboe <jens.axboe@oracle.com>]

On Thu, Apr 19 2007, Jens Axboe wrote:
> > Is it possible that fio was changed?  That it was changed to close() the fd
> > before doing the munmapping whereas it used to hold the file open?
> 
> It's been a while since I tested on this box, so I don't really recall.
> But fio does close() the fd before doing munmap(). This particular test
> case doesn't use mmap(), though.

Ah wait, but it does use mmap! Fio sets up a semaphore my mmap'ing a
file in /tmp (which is reiserfs). Here's a test case that triggers it
100% reliably, adjust /tmp to some other location that is reiserfs.
lockdep from that run attached.

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

int main(int argc, char *argv[])
{
	char fname[] = "/tmp/some_file";	/* /tmp on reiserfs */
	void *p;
	int fd;

	fd = open(fname, O_RDWR|O_CREAT, 0644);
	if (fd < 0) {
		perror("open");
		return 1;
	}

	if (ftruncate(fd, 64) < 0) {
		perror("ftruncate");
		return 1;
	}

	p = mmap(NULL, 64, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	if (p == MAP_FAILED) {
		perror("mmap");
		return 1;
	}

	unlink(fname);
	close(fd);
	munmap(p, 64);
	return 0;
}


=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.21-rc7 #18
-------------------------------------------------------
reiser-mmap/9643 is trying to acquire lock:
 (&inode->i_mutex){--..}, at: [<b038c625>] mutex_lock+0x1c/0x1f

but task is already holding lock:
 (&mm->mmap_sem){----}, at: [<b015c6cf>] sys_munmap+0x26/0x42

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&mm->mmap_sem){----}:
       [<b013e3fb>] __lock_acquire+0xdee/0xf9c
       [<b013e600>] lock_acquire+0x57/0x70
       [<b0137b92>] down_read+0x3a/0x4c
       [<b01b6b88>] reiserfs_remount+0x176/0x42a
       [<b016ba21>] do_remount_sb+0xb9/0x10f
       [<b017ebe7>] do_mount+0x1b6/0x616
       [<b017f0b6>] sys_mount+0x6f/0xa9
       [<b0103f04>] sysenter_past_esp+0x5d/0x99
       [<ffffffff>] 0xffffffff

-> #0 (&inode->i_mutex){--..}:
       [<b013e259>] __lock_acquire+0xc4c/0xf9c
       [<b013e600>] lock_acquire+0x57/0x70
       [<b038c3e5>] __mutex_lock_slowpath+0x73/0x297
       [<b038c625>] mutex_lock+0x1c/0x1f
       [<b01b17e9>] reiserfs_file_release+0x54/0x447
       [<b016afe7>] __fput+0x53/0x101
       [<b016b0ee>] fput+0x19/0x1c
       [<b015bcd5>] remove_vma+0x3b/0x4d
       [<b015c659>] do_munmap+0x17f/0x1cf
       [<b015c6db>] sys_munmap+0x32/0x42
       [<b0103f04>] sysenter_past_esp+0x5d/0x99
       [<ffffffff>] 0xffffffff

other info that might help us debug this:

1 lock held by reiser-mmap/9643:
 #0:  (&mm->mmap_sem){----}, at: [<b015c6cf>] sys_munmap+0x26/0x42

stack backtrace:
 [<b0104f54>] show_trace_log_lvl+0x1a/0x30
 [<b0105626>] show_trace+0x12/0x14
 [<b01056ad>] dump_stack+0x16/0x18
 [<b013c48d>] print_circular_bug_tail+0x68/0x71
 [<b013e259>] __lock_acquire+0xc4c/0xf9c
 [<b013e600>] lock_acquire+0x57/0x70
 [<b038c3e5>] __mutex_lock_slowpath+0x73/0x297
 [<b038c625>] mutex_lock+0x1c/0x1f
 [<b01b17e9>] reiserfs_file_release+0x54/0x447
 [<b016afe7>] __fput+0x53/0x101
 [<b016b0ee>] fput+0x19/0x1c
 [<b015bcd5>] remove_vma+0x3b/0x4d
 [<b015c659>] do_munmap+0x17f/0x1cf
 [<b015c6db>] sys_munmap+0x32/0x42
 [<b0103f04>] sysenter_past_esp+0x5d/0x99
 =======================

-- 
Jens Axboe

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