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Date: Thu, 18 Oct 2012 16:41:49 -0700
From: Mike Waychison <mikew@...gle.com>
To: Seiji Aguchi <seiji.aguchi@....com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
"dzickus@...hat.com" <dzickus@...hat.com>,
"dle-develop@...ts.sourceforge.net"
<dle-develop@...ts.sourceforge.net>,
Satoru Moriya <satoru.moriya@....com>
Subject: Re: [RFC][PATCH 1/2] efi_pstore: hold multiple logs
Resending as text. See below.
On Fri, Oct 5, 2012 at 12:01 PM, Seiji Aguchi <seiji.aguchi@....com> wrote:
> [Problem]
>
> Currently, efi_pstore driver simply overwrites existing panic messages in NVRAM.
> So, in the following scenario, we will lose 1st panic messages.
>
> 1. kernel panics.
> 2. efi_pstore is kicked and write panic messages to NVRAM.
> 3. system reboots.
> 4. kernel panics again before a user checks the 1st panic messages in NVRAM.
>
> [Solution]
>
> This patch takes an approach just holding multiple logs to avoid overwriting existing
> entries.
>
> [Patch Description]
>
> This patch changes write/erase/read callbacks as follows.
>
> - Write callback
> - Check if there are enough spaces to write logs with QueryVariableInfo()
> to avoid handling out of space situation. (It is suggested by Matthew Garrett.)
>
I would prefer to see the exposing query_variable_info callback as a
separate patch. The check in the patch looks good.
> - Remove a logic erasing existing entries.
>
> - Erase callback
> - Freshly create a logic rather than sharing it with a write callback because
> erasing entries doesn't need in a write callback.
>
This sort of change is a lot easier to review if you copy and paste
the routine in a patch separate from this one.
> - Add ctime to an argument.
> Currently, a variable name, which is used to distinguish each log entry, consists of type,
> id and ctime. But an erase callback does not use ctime.
I do not like the way this is plumbed. See below.
>
> If efi_pstore supported just one log, type and id were enough.
>
> On the other hand, in case of supporting multiple logs, ctime is needed to precisely
> distinguish each entry at erasing time.
> Therefore this patch adds ctime to an argument of an erase callback is needed.
>
> - Read callback
> - Add ctime to an argument.
> This change is needed to identify the entry at reading time.
>
> <Example>
>
> As you can see below, we can distinguish first and second events with ctime.
>
> a variable name of first event: dump-type0-1-12345678
> a variable name of second event: dump-type0-1-23456789
>
> type:0
> id:1
> ctime:12345678, 23456789
>
> Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>
> ---
> drivers/acpi/apei/erst.c | 4 +-
> drivers/firmware/efivars.c | 87 ++++++++++++++++++++++++++++----------------
> fs/pstore/inode.c | 3 +-
> fs/pstore/ram.c | 2 +-
> include/linux/efi.h | 1 +
> include/linux/pstore.h | 2 +-
> 6 files changed, 63 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
> index e4d9d24..0bd6ae4 100644
> --- a/drivers/acpi/apei/erst.c
> +++ b/drivers/acpi/apei/erst.c
> @@ -938,7 +938,7 @@ static int erst_writer(enum pstore_type_id type, enum kmsg_dump_reason reason,
> u64 *id, unsigned int part,
> size_t size, struct pstore_info *psi);
> static int erst_clearer(enum pstore_type_id type, u64 id,
> - struct pstore_info *psi);
> + struct timespec time, struct pstore_info *psi);
>
> static struct pstore_info erst_info = {
> .owner = THIS_MODULE,
> @@ -1102,7 +1102,7 @@ static int erst_writer(enum pstore_type_id type, enum kmsg_dump_reason reason,
> }
>
> static int erst_clearer(enum pstore_type_id type, u64 id,
> - struct pstore_info *psi)
> + struct timespec time, struct pstore_info *psi)
> {
> return erst_clear(id);
> }
> diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
> index d10c987..0eaaba3 100644
> --- a/drivers/firmware/efivars.c
> +++ b/drivers/firmware/efivars.c
> @@ -701,23 +701,70 @@ static int efi_pstore_write(enum pstore_type_id type,
> unsigned int part, size_t size, struct pstore_info *psi)
> {
> char name[DUMP_NAME_LEN];
> - char stub_name[DUMP_NAME_LEN];
> efi_char16_t efi_name[DUMP_NAME_LEN];
> efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
> struct efivars *efivars = psi->data;
> - struct efivar_entry *entry, *found = NULL;
> int i, ret = 0;
> + u64 storage_space, remaining_space, max_variable_size;
> + efi_status_t status = EFI_NOT_FOUND;
> +
> + spin_lock(&efivars->lock);
> +
> + /*
> + * Check if there is a space enough to log.
> + * size: a size of logging data
> + * DUMP_NAME_LEN * 2: a maximum size of variable name
> + *
extra line
> + */
> + status = efivars->ops->query_variable_info(PSTORE_EFI_ATTRIBUTES,
> + &storage_space,
> + &remaining_space,
> + &max_variable_size);
> + if (status || remaining_space < size + DUMP_NAME_LEN * 2) {
> + spin_unlock(&efivars->lock);
> + *id = part;
> + return -ENOSPC;
> + }
> +
> + sprintf(name, "dump-type%u-%u-%lu", type, part, get_seconds());
> +
> + for (i = 0; i < DUMP_NAME_LEN; i++)
> + efi_name[i] = name[i];
> +
> + efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
> + size, psi->buf);
> +
> + spin_unlock(&efivars->lock);
> +
> + if (size)
> + ret = efivar_create_sysfs_entry(efivars,
> + utf16_strsize(efi_name,
> + DUMP_NAME_LEN * 2),
> + efi_name, &vendor);
What is happening here? Why is size checked for non-zero?
> +
> + *id = part;
> + return ret;
> +};
> +
> +static int efi_pstore_erase(enum pstore_type_id type, u64 id,
> + struct timespec time, struct pstore_info *psi)
> +{
> + char name[DUMP_NAME_LEN];
> + efi_char16_t efi_name[DUMP_NAME_LEN];
> + efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
> + struct efivars *efivars = psi->data;
> + struct efivar_entry *entry, *found = NULL;
> + int i;
>
> - sprintf(stub_name, "dump-type%u-%u-", type, part);
> - sprintf(name, "%s%lu", stub_name, get_seconds());
> + sprintf(name, "dump-type%u-%llu-%lu", type, id, time.tv_sec);
>
> spin_lock(&efivars->lock);
>
> for (i = 0; i < DUMP_NAME_LEN; i++)
> - efi_name[i] = stub_name[i];
> + efi_name[i] = name[i];
>
> /*
> - * Clean up any entries with the same name
> + * Clean up an entry with the same name
> */
>
> list_for_each_entry(entry, &efivars->list, list) {
> @@ -728,9 +775,6 @@ static int efi_pstore_write(enum pstore_type_id type,
> if (utf16_strncmp(entry->var.VariableName, efi_name,
> utf16_strlen(efi_name)))
> continue;
> - /* Needs to be a prefix */
> - if (entry->var.VariableName[utf16_strlen(efi_name)] == 0)
> - continue;
>
> /* found */
> found = entry;
> @@ -738,37 +782,17 @@ static int efi_pstore_write(enum pstore_type_id type,
> &entry->var.VendorGuid,
> PSTORE_EFI_ATTRIBUTES,
> 0, NULL);
> + break;
> }
>
> if (found)
> list_del(&found->list);
>
> - for (i = 0; i < DUMP_NAME_LEN; i++)
> - efi_name[i] = name[i];
> -
> - efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
> - size, psi->buf);
> -
> spin_unlock(&efivars->lock);
>
> if (found)
> efivar_unregister(found);
>
> - if (size)
> - ret = efivar_create_sysfs_entry(efivars,
> - utf16_strsize(efi_name,
> - DUMP_NAME_LEN * 2),
> - efi_name, &vendor);
> -
> - *id = part;
> - return ret;
> -};
> -
> -static int efi_pstore_erase(enum pstore_type_id type, u64 id,
> - struct pstore_info *psi)
> -{
> - efi_pstore_write(type, 0, &id, (unsigned int)id, 0, psi);
> -
> return 0;
> }
> #else
> @@ -797,7 +821,7 @@ static int efi_pstore_write(enum pstore_type_id type,
> }
>
> static int efi_pstore_erase(enum pstore_type_id type, u64 id,
> - struct pstore_info *psi)
> + struct timespec time, struct pstore_info *psi)
> {
> return 0;
> }
> @@ -1237,6 +1261,7 @@ efivars_init(void)
> ops.get_variable = efi.get_variable;
> ops.set_variable = efi.set_variable;
> ops.get_next_variable = efi.get_next_variable;
> + ops.query_variable_info = efi.query_variable_info;
> error = register_efivars(&__efivars, &ops, efi_kobj);
> if (error)
> goto err_put;
> diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
> index 4ab572e..4300af6 100644
> --- a/fs/pstore/inode.c
> +++ b/fs/pstore/inode.c
> @@ -175,7 +175,8 @@ static int pstore_unlink(struct inode *dir, struct dentry *dentry)
> struct pstore_private *p = dentry->d_inode->i_private;
>
> if (p->psi->erase)
> - p->psi->erase(p->type, p->id, p->psi);
> + p->psi->erase(p->type, p->id, dentry->d_inode->i_ctime,
> + p->psi);
This doesn't look right. What guarantees that the i_ctime means
anything across reboots?
>
> return simple_unlink(dir, dentry);
> }
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 0b311bc..177b281 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -237,7 +237,7 @@ static int ramoops_pstore_write_buf(enum pstore_type_id type,
> }
>
> static int ramoops_pstore_erase(enum pstore_type_id type, u64 id,
> - struct pstore_info *psi)
> + timespec time, struct pstore_info *psi)
> {
> struct ramoops_context *cxt = psi->data;
> struct persistent_ram_zone *prz;
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 8670eb1..c47ec36 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -643,6 +643,7 @@ struct efivar_operations {
> efi_get_variable_t *get_variable;
> efi_get_next_variable_t *get_next_variable;
> efi_set_variable_t *set_variable;
> + efi_query_variable_info_t *query_variable_info;
> };
>
> struct efivars {
> diff --git a/include/linux/pstore.h b/include/linux/pstore.h
> index c892587..71f43e0 100644
> --- a/include/linux/pstore.h
> +++ b/include/linux/pstore.h
> @@ -60,7 +60,7 @@ struct pstore_info {
> unsigned int part, const char *buf, size_t size,
> struct pstore_info *psi);
> int (*erase)(enum pstore_type_id type, u64 id,
> - struct pstore_info *psi);
> + struct timespec time, struct pstore_info *psi);
> void *data;
> };
>
> -- 1.7.1
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