Re: [PATCH v6] f2fs: introduce /sys/fs/f2fs/<disk>/fsck_stack node
From: Chao Yu
Date: Thu Aug 19 2021 - 04:05:28 EST
On 2021/8/16 15:23, 李扬韬 wrote:
HI Chao,
SBI_NEED_FSCK is an indicator that fsck.f2fs needs to be triggered,
this flag is set in too many places. For some scenes that are not very
reproducible, adding stack information will help locate the problem.
Let's record all fsck stack history, I added F2FS_FSCK_STACK_TRACE
configuration options and sysfs nodes. After opening the configuration
options and enabling the node, it will start recording. The recorded
stack information will not be clear, and we can get information form
kernel log.
Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
---
Documentation/ABI/testing/sysfs-fs-f2fs | 7 ++++
fs/f2fs/Kconfig | 10 ++++++
fs/f2fs/f2fs.h | 45 +++++++++++++++++++++++++
fs/f2fs/sysfs.c | 27 +++++++++++++++
4 files changed, 89 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index ef4b9218ae1e..047c398093cf 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -493,3 +493,10 @@ Contact: "Chao Yu" <yuchao0@xxxxxxxxxx>
Description: When ATGC is on, it controls age threshold to bypass GCing young
candidates whose age is not beyond the threshold, by default it was
initialized as 604800 seconds (equals to 7 days).
+
+What: /sys/fs/f2fs/<disk>/fsck_stack
+Date: August 2021
+Contact: "Yangtao Li" <frank.li@xxxxxxxx>
+Description: Controls to enable/disable fsck stack trace, you can get stack
+ information from kernel log. Note that the recorded stack information
+ will not be cleared.
Again, please don't add this into sysfs.
Oh, I missed to check the details...
I added this node, part of the idea is to trigger the export of stack information.
There is no information transmitted through sysfs here, but the record of the stack is switched on and off.
If don't export this information through procfs and sysfs, is there a more appropriate way?
Well, I doubt why we should export stack info via proc/sysfs node or
sysfs switch.
Those info will always be needed to troubleshoot issues no matter in
user or eng version of Android, can we just print them directly into
kernel message... what I concern is we may lost the bug scene due to
no one can help to trigger dmesg printing via sysfs.
Jaegeuk, thoughts?
diff --git a/fs/f2fs/Kconfig b/fs/f2fs/Kconfig
index 7669de7b49ce..f451e567e4a8 100644
--- a/fs/f2fs/Kconfig
+++ b/fs/f2fs/Kconfig
@@ -135,3 +135,13 @@ config F2FS_FS_LZORLE
default y
help
Support LZO-RLE compress algorithm, if unsure, say Y.
+
+config F2FS_FSCK_STACK_TRACE
I don't think we need another config to wrap this functionality, may be we
can use F2FS_CHECK_FS instead.
OK.
+ bool "F2FS fsck stack information record"
+ depends on F2FS_FS
+ depends on STACKDEPOT
+ default y
+ help
+ Support printing out fsck stack history. With this, you have to
+ turn on "fsck_stack" sysfs node. Then you can get information
+ from kernel log.
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ee8eb33e2c25..b2d1d1a5a3fc 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -24,6 +24,8 @@
#include <linux/quotaops.h>
#include <linux/part_stat.h>
#include <crypto/hash.h>
+#include <linux/stackdepot.h>
+#include <linux/stacktrace.h>
#include <linux/fscrypt.h>
#include <linux/fsverity.h>
@@ -117,6 +119,8 @@ typedef u32 nid_t;
#define COMPRESS_EXT_NUM 16
+#define FSCK_STACK_DEPTH 64
16?
OK.
+
struct f2fs_mount_info {
unsigned int opt;
int write_io_size_bits; /* Write IO size bits */
@@ -1748,6 +1752,11 @@ struct f2fs_sb_info {
unsigned int compress_watermark; /* cache page watermark */
atomic_t compress_page_hit; /* cache hit count */
#endif
+#ifdef CONFIG_F2FS_FSCK_STACK_TRACE
+ depot_stack_handle_t *fsck_stack_history;
+ unsigned int fsck_count;
+ bool fsck_stack;
IMO, all bug_on()s are corner cases, and catching those stacks won't cost
much, so we can just use CONFIG_XXX to enable/disable this feature.
F2FS_CHECK_FS ？
+#endif
};
struct f2fs_private_dio {
@@ -1954,6 +1963,38 @@ static inline struct address_space *NODE_MAPPING(struct f2fs_sb_info *sbi)
return sbi->node_inode->i_mapping;
}
+#ifdef CONFIG_F2FS_FSCK_STACK_TRACE
+static void fsck_stack_trace(struct f2fs_sb_info *sbi)
+{
+ unsigned long entries[FSCK_STACK_DEPTH];
+ depot_stack_handle_t stack, *new;
+ unsigned int nr_entries;
+ int i;
+
+ if (!sbi->fsck_stack)
+ return;
+
+ nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
+ nr_entries = filter_irq_stacks(entries, nr_entries);
+ stack = stack_depot_save(entries, nr_entries, GFP_KERNEL);
+ if (!stack)
+ return;
+
+ /* Try to find an existing entry for this backtrace */
+ for (i = 0; i < sbi->fsck_count; i++)
+ if (sbi->fsck_stack_history[i] == stack)
+ return;
+
+ new = krealloc(sbi->fsck_stack_history, (sbi->fsck_count + 1) *
+ sizeof(*sbi->fsck_stack_history), GFP_KERNEL);
+ if (!new)
+ return;
+
+ sbi->fsck_stack_history = new;
+ sbi->fsck_stack_history[sbi->fsck_count++] = stack;
It will case memory leak after f2fs module exits.
So let's enable this feature when f2fs is not a module and enable F2FS_CHECK_FS.
I mean it needs to free .fsck_stack_history during umount().
>
So this is a double-edged sword, and the person who uses it must be aware of this issue.
The release seems unrealistic under the current circumstances. This is also the reason
You mean the handles allocated from stack_depot_save() should not be released, right?
why I add a switch, instead of enabling it by default after opening the configuration.
Well, I still didn't get why we can not release the memory allocated by krealloc().
Thanks,
Yangtao