Hello
On Thursday 19 April 2007 18:15, Jens Axboe wrote:
> 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
>
So, it looks like the problem is that reiserfs_file_release() locks inode's mutex while mm's mmap_sem is locked?
> 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
> =======================
>
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