From: Dave Chinner <david@fromorbit.com>
To: linux-xfs@vger.kernel.org
Subject: [PATCH 1/2] xfs: add mount delay debug option
Date: Tue, 20 Mar 2018 16:00:20 +1100 [thread overview]
Message-ID: <20180320050021.982-2-david@fromorbit.com> (raw)
In-Reply-To: <20180320050021.982-1-david@fromorbit.com>
From: Dave Chinner <dchinner@redhat.com>
Similar to log_recovery_delay, this delay occurs between the VFS
superblock being initialised and the xfs_mount being fully
initialised. It also poisons the per-ag radix tree node so that it
can be used for triggering shrinker races during mount
such as the following:
<run memory pressure workload in background>
$ cat dirty-mount.sh
#! /bin/bash
umount -f /dev/pmem0
mkfs.xfs -f /dev/pmem0
mount /dev/pmem0 /mnt/test
rm -f /mnt/test/foo
xfs_io -fxc "pwrite 0 4k" -c fsync -c "shutdown" /mnt/test/foo
umount /dev/pmem0
# let's crash it now!
echo 30 > /sys/fs/xfs/debug/mount_delay
mount /dev/pmem0 /mnt/test
echo 0 > /sys/fs/xfs/debug/mount_delay
umount /dev/pmem0
$ sudo ./dirty-mount.sh
.....
[ 60.378118] CPU: 3 PID: 3577 Comm: fs_mark Tainted: G D W 4.16.0-rc5-dgc #440
[ 60.378120] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 60.378124] RIP: 0010:radix_tree_next_chunk+0x76/0x320
[ 60.378127] RSP: 0018:ffffc9000276f4f8 EFLAGS: 00010282
[ 60.383670] RAX: a5a5a5a5a5a5a5a4 RBX: 0000000000000010 RCX: 000000000000001a
[ 60.385277] RDX: 0000000000000000 RSI: ffffc9000276f540 RDI: 0000000000000000
[ 60.386554] RBP: 0000000000000000 R08: 0000000000000000 R09: a5a5a5a5a5a5a5a5
[ 60.388194] R10: 0000000000000006 R11: 0000000000000001 R12: ffffc9000276f598
[ 60.389288] R13: 0000000000000040 R14: 0000000000000228 R15: ffff880816cd6458
[ 60.390827] FS: 00007f5c124b9740(0000) GS:ffff88083fc00000(0000) knlGS:0000000000000000
[ 60.392253] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 60.393423] CR2: 00007f5c11bba0b8 CR3: 000000035580e001 CR4: 00000000000606e0
[ 60.394519] Call Trace:
[ 60.395252] radix_tree_gang_lookup_tag+0xc4/0x130
[ 60.395948] xfs_perag_get_tag+0x37/0xf0
[ 60.396522] xfs_reclaim_inodes_count+0x32/0x40
[ 60.397178] xfs_fs_nr_cached_objects+0x11/0x20
[ 60.397837] super_cache_count+0x35/0xc0
[ 60.399159] shrink_slab.part.66+0xb1/0x370
[ 60.400194] shrink_node+0x7e/0x1a0
[ 60.401058] try_to_free_pages+0x199/0x470
[ 60.402081] __alloc_pages_slowpath+0x3a1/0xd20
[ 60.403729] __alloc_pages_nodemask+0x1c3/0x200
[ 60.404941] cache_grow_begin+0x20b/0x2e0
[ 60.406164] fallback_alloc+0x160/0x200
[ 60.407088] kmem_cache_alloc+0x111/0x4e0
[ 60.408038] ? xfs_buf_rele+0x61/0x430
[ 60.408925] kmem_zone_alloc+0x61/0xe0
[ 60.409965] xfs_inode_alloc+0x24/0x1d0
.....
Signed-Off-By: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_globals.c | 1 +
fs/xfs/xfs_super.c | 12 ++++++++++++
fs/xfs/xfs_sysctl.h | 1 +
fs/xfs/xfs_sysfs.c | 31 +++++++++++++++++++++++++++++++
4 files changed, 45 insertions(+)
diff --git a/fs/xfs/xfs_globals.c b/fs/xfs/xfs_globals.c
index 3e1cc3001bcb..fdde17a2333c 100644
--- a/fs/xfs/xfs_globals.c
+++ b/fs/xfs/xfs_globals.c
@@ -47,6 +47,7 @@ xfs_param_t xfs_params = {
struct xfs_globals xfs_globals = {
.log_recovery_delay = 0, /* no delay by default */
+ .mount_delay = 0, /* no delay by default */
#ifdef XFS_ASSERT_FATAL
.bug_on_assert = true, /* assert failures BUG() */
#else
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 4944fe37fc95..ee26437dc567 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1617,6 +1617,18 @@ xfs_fs_fill_super(
#endif
sb->s_op = &xfs_super_operations;
+ /*
+ * Delay mount work if the debug hook is set. This is debug
+ * instrumention to coordinate simulation of xfs mount failures with
+ * VFS superblock operations
+ */
+ if (xfs_globals.mount_delay) {
+ memset(&mp->m_perag_tree, 0xa5, sizeof(mp->m_perag_tree));
+ xfs_notice(mp, "Delaying mount for %d seconds.",
+ xfs_globals.mount_delay);
+ msleep(xfs_globals.mount_delay * 1000);
+ }
+
if (silent)
flags |= XFS_MFSI_QUIET;
diff --git a/fs/xfs/xfs_sysctl.h b/fs/xfs/xfs_sysctl.h
index 82afee005140..b53a33e69932 100644
--- a/fs/xfs/xfs_sysctl.h
+++ b/fs/xfs/xfs_sysctl.h
@@ -95,6 +95,7 @@ extern xfs_param_t xfs_params;
struct xfs_globals {
int log_recovery_delay; /* log recovery delay (secs) */
+ int mount_delay; /* mount setup delay (secs) */
bool bug_on_assert; /* BUG() the kernel on assert failure */
};
extern struct xfs_globals xfs_globals;
diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
index 8b2ccc234f36..2d5cd2529f8e 100644
--- a/fs/xfs/xfs_sysfs.c
+++ b/fs/xfs/xfs_sysfs.c
@@ -165,9 +165,40 @@ log_recovery_delay_show(
}
XFS_SYSFS_ATTR_RW(log_recovery_delay);
+STATIC ssize_t
+mount_delay_store(
+ struct kobject *kobject,
+ const char *buf,
+ size_t count)
+{
+ int ret;
+ int val;
+
+ ret = kstrtoint(buf, 0, &val);
+ if (ret)
+ return ret;
+
+ if (val < 0 || val > 60)
+ return -EINVAL;
+
+ xfs_globals.mount_delay = val;
+
+ return count;
+}
+
+STATIC ssize_t
+mount_delay_show(
+ struct kobject *kobject,
+ char *buf)
+{
+ return snprintf(buf, PAGE_SIZE, "%d\n", xfs_globals.mount_delay);
+}
+XFS_SYSFS_ATTR_RW(mount_delay);
+
static struct attribute *xfs_dbg_attrs[] = {
ATTR_LIST(bug_on_assert),
ATTR_LIST(log_recovery_delay),
+ ATTR_LIST(mount_delay),
NULL,
};
--
2.16.1
next prev parent reply other threads:[~2018-03-20 5:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-20 5:00 [PATCH 0/2] xfs: fix mount vs shrinker race Dave Chinner
2018-03-20 5:00 ` Dave Chinner [this message]
2018-03-20 12:00 ` [PATCH 1/2] xfs: add mount delay debug option Brian Foster
2018-03-20 13:12 ` Dave Chinner
2018-03-20 5:00 ` [PATCH 2/2] xfs: don't shrink the inode cache until after setup completes Dave Chinner
2018-03-20 12:08 ` Brian Foster
2018-03-20 13:21 ` Dave Chinner
2018-03-20 14:21 ` Brian Foster
2018-03-20 22:33 ` Dave Chinner
2018-03-21 11:26 ` Brian Foster
2018-03-21 17:25 ` Darrick J. Wong
2018-05-11 2:09 [PATCH 0/2] xfs: handle mount failures more cleanly Dave Chinner
2018-05-11 2:09 ` [PATCH 1/2] xfs: add mount delay debug option Dave Chinner
2018-05-12 0:28 ` Darrick J. Wong
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180320050021.982-2-david@fromorbit.com \
--to=david@fromorbit.com \
--cc=linux-xfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.