When running low on available disk space and having several processes
doing buffered file IO, I got the following trace in dmesg:
[ 4202.720152] INFO: task kworker/u8:1:5450 blocked for more than 120 seconds.
[ 4202.720401] Not tainted 3.13.0-fdm-btrfs-next-26+ #1
[ 4202.720596] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 4202.720874] kworker/u8:1 D
0000000000000001 0 5450 2 0x00000000
[ 4202.720904] Workqueue: btrfs-flush_delalloc normal_work_helper [btrfs]
[ 4202.720908]
ffff8801f62ddc38 0000000000000082 ffff880203ac2490 00000000001d3f40
[ 4202.720913]
ffff8801f62ddfd8 00000000001d3f40 ffff8800c4f0c920 ffff880203ac2490
[ 4202.720918]
00000000001d4a40 ffff88020fe85a40 ffff88020fe85ab8 0000000000000001
[ 4202.720922] Call Trace:
[ 4202.720931] [<
ffffffff816a3cb9>] schedule+0x29/0x70
[ 4202.720950] [<
ffffffffa01ec48d>] btrfs_start_ordered_extent+0x6d/0x110 [btrfs]
[ 4202.720956] [<
ffffffff8108e620>] ? bit_waitqueue+0xc0/0xc0
[ 4202.720972] [<
ffffffffa01ec559>] btrfs_run_ordered_extent_work+0x29/0x40 [btrfs]
[ 4202.720988] [<
ffffffffa0201987>] normal_work_helper+0x137/0x2c0 [btrfs]
[ 4202.720994] [<
ffffffff810680e5>] process_one_work+0x1f5/0x530
(...)
[ 4202.721027] 2 locks held by kworker/u8:1/5450:
[ 4202.721028] #0: (%s-%s){++++..}, at: [<
ffffffff81068083>] process_one_work+0x193/0x530
[ 4202.721037] #1: ((&work->normal_work)){+.+...}, at: [<
ffffffff81068083>] process_one_work+0x193/0x530
[ 4202.721054] INFO: task btrfs:7891 blocked for more than 120 seconds.
[ 4202.721258] Not tainted 3.13.0-fdm-btrfs-next-26+ #1
[ 4202.721444] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 4202.721699] btrfs D
0000000000000001 0 7891 7890 0x00000001
[ 4202.721704]
ffff88018c2119e8 0000000000000086 ffff8800a33d2490 00000000001d3f40
[ 4202.721710]
ffff88018c211fd8 00000000001d3f40 ffff8802144b0000 ffff8800a33d2490
[ 4202.721714]
ffff8800d8576640 ffff88020fe85bc0 ffff88020fe85bc8 7fffffffffffffff
[ 4202.721718] Call Trace:
[ 4202.721723] [<
ffffffff816a3cb9>] schedule+0x29/0x70
[ 4202.721727] [<
ffffffff816a2ebc>] schedule_timeout+0x1dc/0x270
[ 4202.721732] [<
ffffffff8109bd79>] ? mark_held_locks+0xb9/0x140
[ 4202.721736] [<
ffffffff816a90c0>] ? _raw_spin_unlock_irq+0x30/0x40
[ 4202.721740] [<
ffffffff8109bf0d>] ? trace_hardirqs_on_caller+0x10d/0x1d0
[ 4202.721744] [<
ffffffff816a488f>] wait_for_completion+0xdf/0x120
[ 4202.721749] [<
ffffffff8107fa90>] ? try_to_wake_up+0x310/0x310
[ 4202.721765] [<
ffffffffa01ebee4>] btrfs_wait_ordered_extents+0x1f4/0x280 [btrfs]
[ 4202.721781] [<
ffffffffa020526e>] btrfs_mksubvol.isra.62+0x30e/0x5a0 [btrfs]
[ 4202.721786] [<
ffffffff8108e620>] ? bit_waitqueue+0xc0/0xc0
[ 4202.721799] [<
ffffffffa02056a9>] btrfs_ioctl_snap_create_transid+0x1a9/0x1b0 [btrfs]
[ 4202.721813] [<
ffffffffa020583a>] btrfs_ioctl_snap_create_v2+0x10a/0x170 [btrfs]
(...)
It turns out that extent_io.c:__extent_writepage(), which ends up being called
through filemap_fdatawrite_range() in btrfs_start_ordered_extent(), was getting
-ENOSPC when calling the fill_delalloc callback. In this situation, it returned
without the writepage_end_io_hook callback (inode.c:btrfs_writepage_end_io_hook)
ever being called for the respective page, which prevents the ordered extent's
bytes_left count from ever reaching 0, and therefore a finish_ordered_fn work
is never queued into the endio_write_workers queue. This makes the task that
called btrfs_start_ordered_extent() hang forever on the wait queue of the ordered
extent.
This is fairly easy to reproduce using a small filesystem and fsstress on
a quad core vm:
mkfs.btrfs -f -b `expr 2100 \* 1024 \* 1024` /dev/sdd
mount /dev/sdd /mnt
fsstress -p 6 -d /mnt -n 100000 -x \
"btrfs subvolume snapshot -r /mnt /mnt/mysnap" \
-f allocsp=0 \
-f bulkstat=0 \
-f bulkstat1=0 \
-f chown=0 \
-f creat=1 \
-f dread=0 \
-f dwrite=0 \
-f fallocate=1 \
-f fdatasync=0 \
-f fiemap=0 \
-f freesp=0 \
-f fsync=0 \
-f getattr=0 \
-f getdents=0 \
-f link=0 \
-f mkdir=0 \
-f mknod=0 \
-f punch=1 \
-f read=0 \
-f readlink=0 \
-f rename=0 \
-f resvsp=0 \
-f rmdir=0 \
-f setxattr=0 \
-f stat=0 \
-f symlink=0 \
-f sync=0 \
-f truncate=1 \
-f unlink=0 \
-f unresvsp=0 \
-f write=4
So just ensure that if an error happens while writing the extent page
we call the writepage_end_io_hook callback. Also make it return the
error code and ensure the caller (extent_write_cache_pages) processes
all pages in the page vector even if an error happens only for some
of them, so that ordered extents end up released.
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>
end - cur + 1, 1);
if (IS_ERR_OR_NULL(em)) {
SetPageError(page);
+ ret = PTR_ERR_OR_ZERO(em);
break;
}
set_page_writeback(page);
end_page_writeback(page);
}
+ if (PageError(page)) {
+ ret = ret < 0 ? ret : -EIO;
+ end_extent_writepage(page, ret, start, page_end);
+ }
unlock_page(page);
done_unlocked:
/* drop our reference on any cached states */
free_extent_state(cached_state);
- return 0;
+ return ret;
}
static int eb_wait(void *word)
struct inode *inode = mapping->host;
int ret = 0;
int done = 0;
+ int err = 0;
int nr_to_write_done = 0;
struct pagevec pvec;
int nr_pages;
unlock_page(page);
ret = 0;
}
- if (ret)
- done = 1;
+ if (!err && ret < 0)
+ err = ret;
/*
* the filesystem may choose to bump up nr_to_write.
pagevec_release(&pvec);
cond_resched();
}
- if (!scanned && !done) {
+ if (!scanned && !done && !err) {
/*
* We hit the last page and there is more work to be done: wrap
* back to the start of the file
goto retry;
}
btrfs_add_delayed_iput(inode);
- return ret;
+ return err;
}
static void flush_epd_write_bio(struct extent_page_data *epd)
projects / linux.git / commitdiff