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Commit b77f6fa5 authored by Jin Qian's avatar Jin Qian
Browse files

ANDROID: uid_sys_stats: fix negative write bytes. 



A task can cancel writes made by other tasks. In rare cases,
cancelled_write_bytes is larger than write_bytes if the task
itself didn't make any write. This doesn't affect total size
but may cause confusion when looking at IO usage on individual
tasks.

Bug: 35851986
Change-Id: If6cb549aeef9e248e18d804293401bb2b91918ca
Signed-off-by: default avatarJin Qian <jinqian@google.com>
parent e90f210d

drivers/misc/uid_sys_stats.c

+10 −4
Original line number Diff line number Diff line
@@ -215,14 +215,21 @@ static const struct file_operations uid_remove_fops = { 
	.write		= uid_remove_write,

};



static u64 compute_write_bytes(struct task_struct *task)

{

	if (task->ioac.write_bytes <= task->ioac.cancelled_write_bytes)

		return 0;



	return task->ioac.write_bytes - task->ioac.cancelled_write_bytes;

}



static void add_uid_io_curr_stats(struct uid_entry *uid_entry,

			struct task_struct *task)

{

	struct io_stats *io_curr = &uid_entry->io[UID_STATE_TOTAL_CURR];



	io_curr->read_bytes += task->ioac.read_bytes;

	io_curr->write_bytes +=

		task->ioac.write_bytes - task->ioac.cancelled_write_bytes;

	io_curr->write_bytes += compute_write_bytes(task);

	io_curr->rchar += task->ioac.rchar;

	io_curr->wchar += task->ioac.wchar;

}
@@ -233,8 +240,7 @@ static void clean_uid_io_last_stats(struct uid_entry *uid_entry, 
	struct io_stats *io_last = &uid_entry->io[UID_STATE_TOTAL_LAST];



	io_last->read_bytes -= task->ioac.read_bytes;

	io_last->write_bytes -=

		task->ioac.write_bytes - task->ioac.cancelled_write_bytes;

	io_last->write_bytes -= compute_write_bytes(task);

	io_last->rchar -= task->ioac.rchar;

	io_last->wchar -= task->ioac.wchar;

}