Re: [PATCH v4 06/12] pstore/blk: Add console frontend support

From: WeiXiong Liao
Date: Sat May 09 2020 - 00:53:07 EST

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In reply to: Kees Cook: "[PATCH v4 06/12] pstore/blk: Add console frontend support"
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hi Kees Cook,

On 2020/5/8 PM 2:39, Kees Cook wrote:
> From: WeiXiong Liao <liaoweixiong@xxxxxxxxxxxxxxxxx>
>
> Support backend for console. To enable console backend, just make
> console_size be greater than 0 and a multiple of 4096.
>
> Signed-off-by: WeiXiong Liao <liaoweixiong@xxxxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/r/1585126506-18635-6-git-send-email-liaoweixiong@xxxxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> fs/pstore/Kconfig | 12 +++++++
> fs/pstore/blk.c | 12 ++++++-
> fs/pstore/zone.c | 67 +++++++++++++++++++++++++++++++++++--
> include/linux/pstore_zone.h | 4 ++-
> 4 files changed, 90 insertions(+), 5 deletions(-)
>
> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
> index f18cd126d83f..f1484f751c5e 100644
> --- a/fs/pstore/Kconfig
> +++ b/fs/pstore/Kconfig
> @@ -236,3 +236,15 @@ config PSTORE_BLK_PMSG_SIZE
>
> NOTE that, both Kconfig and module parameters can configure
> pstore/blk, but module parameters have priority over Kconfig.
> +
> +config PSTORE_BLK_CONSOLE_SIZE
> + int "Size in Kbytes of console to store"
> + depends on PSTORE_BLK
> + depends on PSTORE_CONSOLE
> + default 64
> + help
> + This just sets size of console (console_size) for pstore/blk. The
> + size is in KB and must be a multiple of 4.
> +
> + NOTE that, both Kconfig and module parameters can configure
> + pstore/blk, but module parameters have priority over Kconfig.
> diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
> index 401e5ba66a5f..813025ea7edd 100644
> --- a/fs/pstore/blk.c
> +++ b/fs/pstore/blk.c
> @@ -32,6 +32,14 @@ static long pmsg_size = -1;
> module_param(pmsg_size, long, 0400);
> MODULE_PARM_DESC(pmsg_size, "pmsg size in kbytes");
>
> +#if IS_ENABLED(CONFIG_PSTORE_CONSOLE)
> +static long console_size = CONFIG_PSTORE_BLK_CONSOLE_SIZE;
> +#else
> +static long console_size = -1;
> +#endif
> +module_param(console_size, long, 0400);
> +MODULE_PARM_DESC(console_size, "console size in kbytes");
> +
> /*
> * blkdev - The block device to use.
> *
> @@ -83,7 +91,8 @@ static struct bdev_info {
> * whole disk).
> * On success, the number of bytes should be returned, others
> * means error.
> - * @write: The same as @read.
> + * @write: The same as @read, but the following error number:
> + * -EBUSY means try to write again later.
> * @panic_write:The write operation only used for panic case. It's optional
> * if you do not care panic log. The parameters and return value
> * are the same as @read.
> @@ -133,6 +142,7 @@ static int psblk_register_do(struct psblk_device *dev)
>
> verify_size(kmsg_size, 4096, dev->flags & PSTORE_FLAGS_DMESG);
> verify_size(pmsg_size, 4096, dev->flags & PSTORE_FLAGS_PMSG);
> + verify_size(console_size, 4096, dev->flags & PSTORE_FLAGS_CONSOLE);
> #undef verify_size
>
> pstore_zone_info->total_size = dev->total_size;
> diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
> index f472b06a6c14..0b952eea39fe 100644
> --- a/fs/pstore/zone.c
> +++ b/fs/pstore/zone.c
> @@ -87,10 +87,12 @@ struct pstore_zone {
> *
> * @opszs: oops/panic storage zones
> * @ppsz: pmsg storage zone
> + * @cpsz: console storage zone
> * @oops_max_cnt: max count of @opszs
> * @oops_read_cnt: counter to read oops zone
> * @oops_write_cnt: counter to write
> * @pmsg_read_cnt: counter to read pmsg zone
> + * @console_read_cnt: counter to read console zone
> * @oops_counter: counter to oops
> * @panic_counter: counter to panic
> * @recovered: whether finish recovering data from storage
> @@ -102,10 +104,12 @@ struct pstore_zone {
> struct psz_context {
> struct pstore_zone **opszs;
> struct pstore_zone *ppsz;
> + struct pstore_zone *cpsz;
> unsigned int oops_max_cnt;
> unsigned int oops_read_cnt;
> unsigned int oops_write_cnt;
> unsigned int pmsg_read_cnt;
> + unsigned int console_read_cnt;
> /*
> * the counter should be recovered when recover.
> * It records the oops/panic times after burning rather than booting.
> @@ -125,6 +129,9 @@ struct psz_context {
> };
> static struct psz_context psz_cxt;
>
> +static void psz_flush_all_dirty_zones(struct work_struct *);
> +static DECLARE_WORK(psz_cleaner, psz_flush_all_dirty_zones);

I think it's better to use delayed work.

static DECLARE_DELAYED_WORK(psz_cleaner, psz_flush_all_dirty_zones);

> +
> /**
> * enum psz_flush_mode - flush mode for psz_zone_write()
> *
> @@ -235,6 +242,9 @@ static int psz_zone_write(struct pstore_zone *zone,
> return 0;
> dirty:
> atomic_set(&zone->dirty, true);
> + /* flush dirty zones nicely */
> + if (wcnt == -EBUSY && !is_on_panic())
> + schedule_work(&psz_cleaner);

Change to:

schedule_delayed_work(&psz_cleaner, msecs_to_jiffies(500));

delay for 500ms to merge more log of console and reduce calling times.

> return -EBUSY;
> }
>
> @@ -291,6 +301,15 @@ static int psz_move_zone(struct pstore_zone *old, struct pstore_zone *new)
> return 0;
> }
>
> +static void psz_flush_all_dirty_zones(struct work_struct *work)
> +{
> + struct psz_context *cxt = &psz_cxt;
> +
> + psz_flush_dirty_zone(cxt->ppsz);
> + psz_flush_dirty_zone(cxt->cpsz);
> + psz_flush_dirty_zones(cxt->opszs, cxt->oops_max_cnt);

If flush dirty failed, I think it should try again later.

int ret = 0;

ret |= psz_flush_dirty_zone(cxt->ppsz);
ret |= psz_flush_dirty_zone(cxt->cpsz);
ret |= psz_flush_dirty_zones(cxt->opszs, cxt->oops_max_cnt);
if (ret)
schedule_delayed_work(&psz_cleaner, msecs_to_jiffies(1000));

And add this diff:

@@ -714,10 +717,10 @@ static int notrace psz_oops_write(struct
psz_context *cxt,
return -ENOSPC;

ret = psz_oops_write_record(cxt, record);
- if (!ret) {
+ if (!ret && is_on_panic()) {
+ /* ensure all data are flushed to storage when panic */
pr_debug("try to flush other dirty zones\n");
- psz_flush_dirty_zones(cxt->opszs, cxt->oops_max_cnt);
- psz_flush_dirty_zone(cxt->ppsz);
+ psz_flush_all_dirty_zones(NULL);
}

/* always return 0 as we had handled it on buffer */

We should flush only when panic since all the dirty zones will be flushed by
delayed_work after this patch.

> +}
> +> static int psz_recover_oops_data(struct psz_context *cxt)
> {
> struct pstore_zone_info *info = cxt->pstore_zone_info;
> @@ -546,6 +565,10 @@ static inline int psz_recovery(struct psz_context *cxt)
> if (ret)
> goto recover_fail;
>
> + ret = psz_recover_zone(cxt, cxt->cpsz);
> + if (ret)
> + goto recover_fail;
> +
> pr_debug("recover end!\n");
> atomic_set(&cxt->recovered, 1);
> return 0;
> @@ -561,6 +584,7 @@ static int psz_pstore_open(struct pstore_info *psi)
>
> cxt->oops_read_cnt = 0;
> cxt->pmsg_read_cnt = 0;
> + cxt->console_read_cnt = 0;
> return 0;
> }
>
> @@ -625,8 +649,9 @@ static int psz_pstore_erase(struct pstore_record *record)
> return psz_oops_erase(cxt, cxt->opszs[record->id], record);
> case PSTORE_TYPE_PMSG:
> return psz_record_erase(cxt, cxt->ppsz);
> - default:
> - return -EINVAL;
> + case PSTORE_TYPE_CONSOLE:
> + return psz_record_erase(cxt, cxt->cpsz);
> + default: return -EINVAL;
> }
> }
>
> @@ -753,9 +778,18 @@ static int notrace psz_pstore_write(struct pstore_record *record)
> record->reason == KMSG_DUMP_PANIC)
> atomic_set(&cxt->on_panic, 1);
>
> + /*
> + * if on panic, do not write except panic records
> + * Fix case that panic_write prints log which wakes up console backend.
> + */
> + if (is_on_panic() && record->type != PSTORE_TYPE_DMESG)
> + return -EBUSY;
> +
> switch (record->type) {
> case PSTORE_TYPE_DMESG:
> return psz_oops_write(cxt, record);
> + case PSTORE_TYPE_CONSOLE:
> + return psz_record_write(cxt->cpsz, record);
> case PSTORE_TYPE_PMSG:
> return psz_record_write(cxt->ppsz, record);
> default:
> @@ -780,6 +814,13 @@ static struct pstore_zone *psz_read_next_zone(struct psz_context *cxt)
> return zone;
> }
>
> + if (cxt->console_read_cnt == 0) {
> + cxt->console_read_cnt++;
> + zone = cxt->cpsz;
> + if (psz_old_ok(zone))
> + return zone;
> + }
> +
> return NULL;
> }
>
> @@ -890,6 +931,8 @@ static ssize_t psz_pstore_read(struct pstore_record *record)
> readop = psz_oops_read;
> record->id = cxt->oops_read_cnt - 1;
> break;
> + case PSTORE_TYPE_CONSOLE:
> + fallthrough;
> case PSTORE_TYPE_PMSG:
> readop = psz_record_read;
> break;
> @@ -1037,6 +1080,8 @@ static void psz_free_all_zones(struct psz_context *cxt)
> psz_free_zones(&cxt->opszs, &cxt->oops_max_cnt);
> if (cxt->ppsz)
> psz_free_zone(&cxt->ppsz);
> + if (cxt->cpsz)
> + psz_free_zone(&cxt->cpsz);
> }
>
> static int psz_alloc_zones(struct psz_context *cxt)
> @@ -1053,6 +1098,14 @@ static int psz_alloc_zones(struct psz_context *cxt)
> goto free_out;
> }
>
> + off_size += info->console_size;
> + cxt->cpsz = psz_init_zone(PSTORE_TYPE_CONSOLE, &off,
> + info->console_size);
> + if (IS_ERR(cxt->cpsz)) {
> + err = PTR_ERR(cxt->cpsz);
> + goto free_out;
> + }
> +
> cxt->opszs = psz_init_zones(PSTORE_TYPE_DMESG, &off,
> info->total_size - off_size,
> info->kmsg_size, &cxt->oops_max_cnt);
> @@ -1086,7 +1139,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
> return -EINVAL;
> }
>
> - if (!info->kmsg_size && !info->pmsg_size) {
> + if (!info->kmsg_size && !info->pmsg_size && !info->console_size) {
> pr_warn("at least one of the records be non-zero\n");
> return -EINVAL;
> }
> @@ -1114,6 +1167,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
> check_size(total_size, 4096);
> check_size(kmsg_size, SECTOR_SIZE);
> check_size(pmsg_size, SECTOR_SIZE);
> + check_size(console_size, SECTOR_SIZE);
>
> #undef check_size
>
> @@ -1141,6 +1195,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
> pr_debug("\ttotal size : %ld Bytes\n", info->total_size);
> pr_debug("\toops size : %ld Bytes\n", info->kmsg_size);
> pr_debug("\tpmsg size : %ld Bytes\n", info->pmsg_size);
> + pr_debug("\tconsole size : %ld Bytes\n", info->console_size);
>
> err = psz_alloc_zones(cxt);
> if (err) {
> @@ -1173,6 +1228,10 @@ int register_pstore_zone(struct pstore_zone_info *info)
> cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
> pr_cont(" pmsg");
> }
> + if (info->console_size) {
> + cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
> + pr_cont(" console");
> + }
> pr_cont("\n");
>
> err = pstore_register(&cxt->pstore);
> @@ -1204,6 +1263,8 @@ void unregister_pstore_zone(struct pstore_zone_info *info)
> {
> struct psz_context *cxt = &psz_cxt;
>
> + flush_work(&psz_cleaner);
> +

I think it should try to flush dirty zones before unregister in case of
lost data.

psz_flush_all_dirty_zones(NULL);
flush_delayed_work(&psz_cleaner);

> pstore_unregister(&cxt->pstore);
> kfree(cxt->pstore.buf);
> cxt->pstore.bufsize = 0;
> diff --git a/include/linux/pstore_zone.h b/include/linux/pstore_zone.h
> index 39c2cb944123..da294e6d7661 100644
> --- a/include/linux/pstore_zone.h
> +++ b/include/linux/pstore_zone.h
> @@ -18,11 +18,12 @@ typedef ssize_t (*psz_write_op)(const char *, size_t, loff_t);
> * it must be multiple of SECTOR_SIZE(512 Bytes).
> * @max_reason: Maximum kmsg dump reason to store.
> * @pmsg_size: The size of pmsg zone which is the same as @kmsg_size.
> + * @console_size:The size of console zone which is the same as @kmsg_size.
> * @read: The general read operation. Both of the function parameters
> * @size and @offset are relative value to storage.
> * On success, the number of bytes should be returned, others
> * means error.
> - * @write: The same as @read.
> + * @write: The same as @read, but -EBUSY means try to write again later.
> * @panic_write:The write operation only used for panic case. It's optional
> * if you do not care panic log. The parameters and return value
> * are the same as @read.
> @@ -35,6 +36,7 @@ struct pstore_zone_info {
> unsigned long kmsg_size;
> int max_reason;
> unsigned long pmsg_size;
> + unsigned long console_size;
> psz_read_op read;
> psz_write_op write;
> psz_write_op panic_write;
>

--
WeiXiong Liao

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