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List: linux-api
Subject: [PATCH 0/7] Report more information in fanotify dirent events
From: Amir Goldstein <amir73il () gmail ! com>
Date: 2021-10-29 11:40:21
Message-ID: 20211029114028.569755-1-amir73il () gmail ! com
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Jan,
This patch set follows up on the discussion on FAN_REPORT_TARGET_FID [1]
from 3 months ago.
With FAN_REPORT_PIDFD in 5.15 and FAN_FS_ERROR on its way to 5.16,
I figured we could get an early (re)start of the discussion on
FAN_REPORT_TARGET_FID towards 5.17.
The added information in dirent events solves problems for my use case -
It helps getting the following information in a race free manner:
1. fid of a created directory on mkdir
2. from/to path information on rename of non-dir
I realize those are two different API traits, but they are close enough
so I preferred not to clutter the REPORT flags space any further than it
already is. The single added flag FAN_REPORT_TARGET_FID adds:
1. child fid info to CREATE/DELETE/MOVED_* events
2. new parent+name info to MOVED_FROM event
Instead of going the "inotify way" and trying to join the MOVED_FROM/
MOVED_TO events using a cookie, I chose to incorporate the new
parent+name intomation only in the MOVED_FROM event.
I made this choice for several reasons:
1. Availability of the moved dentry in the hook and event data
2. First info record is the old parent+name, like FAN_REPORT_DFID_NAME
3. Unlike, MOVED_TO, MOVED_FROM was useless for applications that use
DFID_NAME info to statat(2) the object as we suggested
I chose to reduce testing complexity and require all other FID
flags with FAN_REPORT_TARGET_FID and there is a convenience
macro FAN_REPORT_ALL_FIDS that application can use.
This restriction could be relaxed in the future if we have a good reason
to do so.
Since the POC branch 3 months ago, I dropped the 'sub_type' field of
the info header, because it did not add much value IMO.
Patches [2] and LTP test [3] are available on my github.
Thanks,
Amir.
[1] https://lore.kernel.org/linux-fsdevel/CAOQ4uxjYDDk00VPdWtRB1_tf+gCoPFgSQ9O0p0fGaW_JiFUUKA@mail.gmail.com/
[2] https://github.com/amir73il/linux/commits/fanotify_target_fid
[3] https://github.com/amir73il/ltp/commits/fanotify_target_fid
Amir Goldstein (7):
fsnotify: pass dentry instead of inode data for move events
fanotify: introduce group flag FAN_REPORT_TARGET_FID
fanotify: use macros to get the offset to fanotify_info buffer
fanotify: support secondary dir fh and name in fanotify_info
fanotify: record new parent and name in MOVED_FROM event
fanotify: report new parent and name in MOVED_FROM event
fanotify: enable the FAN_REPORT_TARGET_FID flag
fs/notify/fanotify/fanotify.c | 108 ++++++++++++++++++++++-----
fs/notify/fanotify/fanotify.h | 113 +++++++++++++++++++++++++----
fs/notify/fanotify/fanotify_user.c | 43 +++++++++--
include/linux/fanotify.h | 2 +-
include/linux/fsnotify.h | 7 +-
include/uapi/linux/fanotify.h | 5 ++
6 files changed, 235 insertions(+), 43 deletions(-)
--
2.33.1
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