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Date: Mon, 18 Oct 2021 10:55:06 -0300
From: Gabriel Krisman Bertazi <krisman@...labora.com>
To: Amir Goldstein <amir73il@...il.com>
Cc: Jan Kara <jack@...e.com>, "Darrick J. Wong" <djwong@...nel.org>,
Theodore Tso <tytso@....edu>,
David Howells <dhowells@...hat.com>,
Khazhismel Kumykov <khazhy@...gle.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Ext4 <linux-ext4@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>,
Matthew Bobrowski <repnop@...gle.com>, kernel@...labora.com
Subject: Re: [PATCH v7 21/28] fanotify: Support merging of error events
Amir Goldstein <amir73il@...il.com> writes:
> On Fri, Oct 15, 2021 at 7:54 PM Gabriel Krisman Bertazi
> <krisman@...labora.com> wrote:
>>
>> Amir Goldstein <amir73il@...il.com> writes:
>>
>> > On Fri, Oct 15, 2021 at 12:39 AM Gabriel Krisman Bertazi
>> > <krisman@...labora.com> wrote:
>> >>
>> >> Error events (FAN_FS_ERROR) against the same file system can be merged
>> >> by simply iterating the error count. The hash is taken from the fsid,
>> >> without considering the FH. This means that only the first error object
>> >> is reported.
>> >>
>> >> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
>> >> ---
>> >> fs/notify/fanotify/fanotify.c | 39 ++++++++++++++++++++++++++++++++---
>> >> fs/notify/fanotify/fanotify.h | 4 +++-
>> >> 2 files changed, 39 insertions(+), 4 deletions(-)
>> >>
>> >> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
>> >> index 9b970359570a..7032083df62a 100644
>> >> --- a/fs/notify/fanotify/fanotify.c
>> >> +++ b/fs/notify/fanotify/fanotify.c
>> >> @@ -111,6 +111,16 @@ static bool fanotify_name_event_equal(struct fanotify_name_event *fne1,
>> >> return fanotify_info_equal(info1, info2);
>> >> }
>> >>
>> >> +static bool fanotify_error_event_equal(struct fanotify_error_event *fee1,
>> >> + struct fanotify_error_event *fee2)
>> >> +{
>> >> + /* Error events against the same file system are always merged. */
>> >> + if (!fanotify_fsid_equal(&fee1->fsid, &fee2->fsid))
>> >> + return false;
>> >> +
>> >> + return true;
>> >> +}
>> >> +
>> >> static bool fanotify_should_merge(struct fanotify_event *old,
>> >> struct fanotify_event *new)
>> >> {
>> >> @@ -141,6 +151,9 @@ static bool fanotify_should_merge(struct fanotify_event *old,
>> >> case FANOTIFY_EVENT_TYPE_FID_NAME:
>> >> return fanotify_name_event_equal(FANOTIFY_NE(old),
>> >> FANOTIFY_NE(new));
>> >> + case FANOTIFY_EVENT_TYPE_FS_ERROR:
>> >> + return fanotify_error_event_equal(FANOTIFY_EE(old),
>> >> + FANOTIFY_EE(new));
>> >> default:
>> >> WARN_ON_ONCE(1);
>> >> }
>> >> @@ -148,6 +161,22 @@ static bool fanotify_should_merge(struct fanotify_event *old,
>> >> return false;
>> >> }
>> >>
>> >> +static void fanotify_merge_error_event(struct fanotify_error_event *dest,
>> >> + struct fanotify_error_event *origin)
>> >> +{
>> >> + dest->err_count++;
>> >> +}
>> >> +
>> >> +static void fanotify_merge_event(struct fanotify_event *dest,
>> >> + struct fanotify_event *origin)
>> >> +{
>> >> + dest->mask |= origin->mask;
>> >> +
>> >> + if (origin->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
>> >> + fanotify_merge_error_event(FANOTIFY_EE(dest),
>> >> + FANOTIFY_EE(origin));
>> >> +}
>> >> +
>> >> /* Limit event merges to limit CPU overhead per event */
>> >> #define FANOTIFY_MAX_MERGE_EVENTS 128
>> >>
>> >> @@ -175,7 +204,7 @@ static int fanotify_merge(struct fsnotify_group *group,
>> >> if (++i > FANOTIFY_MAX_MERGE_EVENTS)
>> >> break;
>> >> if (fanotify_should_merge(old, new)) {
>> >> - old->mask |= new->mask;
>> >> + fanotify_merge_event(old, new);
>> >> return 1;
>> >> }
>> >> }
>> >> @@ -577,7 +606,8 @@ static struct fanotify_event *fanotify_alloc_name_event(struct inode *id,
>> >> static struct fanotify_event *fanotify_alloc_error_event(
>> >> struct fsnotify_group *group,
>> >> __kernel_fsid_t *fsid,
>> >> - const void *data, int data_type)
>> >> + const void *data, int data_type,
>> >> + unsigned int *hash)
>> >> {
>> >> struct fs_error_report *report =
>> >> fsnotify_data_error_report(data, data_type);
>> >> @@ -591,6 +621,9 @@ static struct fanotify_event *fanotify_alloc_error_event(
>> >> return NULL;
>> >>
>> >> fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
>> >> + fee->err_count = 1;
>> >> +
>> >> + *hash ^= fanotify_hash_fsid(fsid);
>> >>
>> >> return &fee->fae;
>> >> }
>> >
>> > Forgot to store fee->fsid?
>>
>> Not really. this is part of the FID info record support, which is done
>> in patch 23.
>>
>
> Sure, it does not really matter for bisection when FS_ERROR is not yet
> wired, but it is weird to compare event fsid's when they have not been
> initialized.
>
> Logically, storing the fsid in this patch would be better.
Makes sense. Will do!
Thanks,
--
Gabriel Krisman Bertazi
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