[RFC][PATCH v4 3/3] efi_pstore: Skiping scheduling a workqueue incases other than oops

[Seiji Aguchi]

[Problem]
 efi_pstore creates sysfs files when logging kernel messages to NVRAM.
 Currently, the sysfs files are updated in a workqueue which is registered in a write callback.

 On the other hand, situations which users needs the sysfs files are when they erase entries or oops happen 
 because a system will  be down and users can't access to sysfs files in other cases like panic, reboot or emergency_restart.

 Also, if kernel panics due to a bug of workqueue operations and a write callback of efi_pstore is called in
 panic case, efi_pstore may fail due to a failure of schedule_work(). 
 And panic_notifier_chain()/emergency_restart() is not kicked if efi_pstore fails.  
   This may cause user's unwanted result.

[Patch Description]
 This patch registers a workqueue updating sysfs entries in cases where users erase entries or oops happen only,
 and skips it in other cases like panic, reboot or emergency_start.

Signed-off-by: Seiji Aguchi <seiji.aguchi@xxxxxxx>
---
 drivers/firmware/efivars.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index cd16ea6..d5911fd 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -746,7 +746,12 @@ static int efi_pstore_write(enum pstore_type_id type,
 
 	spin_unlock_irqrestore(&efivars->lock, flags);
 
-	schedule_work(&efivar_work);
+	/*
+	 * The user may want to update sysfs for this write
+	 * when they erase an entry via /dev/pstore or oops happen.
+	 */
+	if (!size || reason == KMSG_DUMP_OOPS)
+		schedule_work(&efivar_work);
 
 	*id = part;
 	return ret;
-- 1.7.1
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