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ANDROID: uid_sys_stats: fix negative write bytes.

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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: Jin Qian <jinqian@google.com>
This commit is contained in:
Jin Qian 2017-02-28 15:09:42 -08:00 committed by Amit Pundir
parent 396f015c5d
commit 0d1e81ffe0
1 changed files with 10 additions and 4 deletions
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14
drivers/misc/uid_sys_stats.c
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@ -200,14 +200,21 @@ 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;
}
@ -218,8 +225,7 @@ 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;
}