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[92.109.99.123]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43d8fbc1716sm121247545e9.15.2025.03.31.06.51.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Mar 2025 06:51:04 -0700 (PDT) From: Amir Goldstein To: Alejandro Colomar Cc: Miklos Szeredi , Jan Kara , Christian Brauner , linux-man@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH] fanotify: Document mount namespace events Date: Mon, 31 Mar 2025 15:51:01 +0200 Message-Id: <20250331135101.1436770-1-amir73il@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Used to subscribe for notifications for when mounts are attached/detached from a mount namespace. Cc: Jan Kara Cc: Miklos Szeredi Cc: Christian Brauner Signed-off-by: Amir Goldstein Reviewed-by: Christian Brauner --- Alejandro, This feature was also added (by Miklos) in v6.14. The man page patch can be merged independently of the FAN_PRE_ACCESS patch. However, this patch depends on the FAN_FS_ERROR cleanup patch that I just posted, because of the reordering of event entries. Thanks, Amir. man/man2/fanotify_init.2 | 20 ++++++++++++++++++++ man/man2/fanotify_mark.2 | 35 ++++++++++++++++++++++++++++++++++- man/man7/fanotify.7 | 39 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 93 insertions(+), 1 deletion(-) diff --git a/man/man2/fanotify_init.2 b/man/man2/fanotify_init.2 index 699b6f054..26289c496 100644 --- a/man/man2/fanotify_init.2 +++ b/man/man2/fanotify_init.2 @@ -330,6 +330,26 @@ that the directory entry is referring to. This is a synonym for .RB ( FAN_REPORT_DFID_NAME | FAN_REPORT_FID | FAN_REPORT_TARGET_FID ). .TP +.BR FAN_REPORT_MNT " (since Linux 6.14)" +.\" commit 0f46d81f2bce970b1c562aa3c944a271bbec2729 +This value allows the receipt of events which contain additional information +about the underlying mount correlated to an event. +An additional record of type +.B FAN_EVENT_INFO_TYPE_MNT +encapsulates the information about the mount and is included alongside the +generic event metadata structure. +The use of +.BR FAN_CLASS_CONTENT , +.BR FAN_CLASS_PRE_CONTENT, +or any of the +.B FAN_REPORT_DFID_NAME_TARGET +flags along with this flag is not permitted +and will result in the error +.BR EINVAL . +See +.BR fanotify (7) +for additional details. +.TP .BR FAN_REPORT_PIDFD " (since Linux 5.15 and 5.10.220)" .\" commit af579beb666aefb17e9a335c12c788c92932baf1 Events for fanotify groups initialized with this flag will contain diff --git a/man/man2/fanotify_mark.2 b/man/man2/fanotify_mark.2 index da569279b..b843c1f9a 100644 --- a/man/man2/fanotify_mark.2 +++ b/man/man2/fanotify_mark.2 @@ -67,7 +67,8 @@ contains all marks for filesystems are removed from the group. Otherwise, all marks for directories and files are removed. No flag other than, and at most one of, the flags -.B FAN_MARK_MOUNT +.BR FAN_MARK_MNTNS , +.BR FAN_MARK_MOUNT , or .B FAN_MARK_FILESYSTEM can be used in conjunction with @@ -99,6 +100,20 @@ If the filesystem object to be marked is not a directory, the error .B ENOTDIR shall be raised. .TP +.BR FAN_MARK_MNTNS " (since Linux 6.14)" +.\" commit 0f46d81f2bce970b1c562aa3c944a271bbec2729 +Mark the mount namespace of the path specified by +.IR pathname . +If +.I pathname +is not itself a mount point, +the mount namespace of the mount containing +.I pathname +will be marked. +An fanotify group that is initialized with flag +.B FAN_REPORT_MNT +is required. +.TP .B FAN_MARK_MOUNT Mark the mount specified by .IR pathname . @@ -395,6 +410,24 @@ Create an event when a marked file or directory itself has been moved. An fanotify group that identifies filesystem objects by file handles is required. .TP +.BR FAN_MNT_ATTACH ", " FAN_MNT_DETACH " (since Linux 6.14)" +.\" commit 0f46d81f2bce970b1c562aa3c944a271bbec2729 +Create an event when a mount was attached to or detached from a marked mount namespace. +An attempt to set this flag on an inode, mount or filesystem mark +will result in the error +.BR EINVAL . +An fanotify group that is initialized with flag +.B FAN_REPORT_MNT +and the mark flag +.B FAN_MARK_MNTNS +are required. +An additional information record of type +.B FAN_EVENT_INFO_TYPE_MNT +is returned with the event. +See +.BR fanotify (7) +for additional details. +.TP .BR FAN_FS_ERROR " (since Linux 5.16, 5.15.154, and 5.10.220)" .\" commit 9709bd548f11a092d124698118013f66e1740f9b Create an event when a filesystem error diff --git a/man/man7/fanotify.7 b/man/man7/fanotify.7 index 77dcb8aa5..98705c3c7 100644 --- a/man/man7/fanotify.7 +++ b/man/man7/fanotify.7 @@ -228,6 +228,23 @@ struct fanotify_event_info_pidfd { .EE .in .P +In cases where an fanotify group is initialized with +.BR FAN_REPORT_MNT , +event listeners should expect to receive the below +information record object alongside the generic +.I fanotify_event_metadata +structure within the read buffer. +This structure is defined as follows: +.P +.in +4n +.EX +struct fanotify_event_info_mnt { + struct fanotify_event_info_header hdr; + __u64 mnt_id; +}; +.EE +.in +.P In case of a .B FAN_FS_ERROR event, @@ -442,6 +459,12 @@ A file or directory that was opened read-only .RB ( O_RDONLY ) was closed. .TP +.BR FAN_MNT_ATTACH +A mount was attached to mount namespace. +.TP +.BR FAN_MNT_DETACH +A mount was detached to mount namespace. +.TP .B FAN_FS_ERROR A filesystem error was detected. .TP @@ -540,6 +563,7 @@ The value of this field can be set to one of the following: .BR FAN_EVENT_INFO_TYPE_FID , .BR FAN_EVENT_INFO_TYPE_DFID , .BR FAN_EVENT_INFO_TYPE_DFID_NAME , +.BR FAN_EVENT_INFO_TYPE_MNT , .BR FAN_EVENT_INFO_TYPE_ERROR , .BR FAN_EVENT_INFO_TYPE_RANGE , or @@ -727,6 +751,21 @@ in case of a terminated process, the value will be .BR \-ESRCH . .P The fields of the +.I fanotify_event_info_mnt +structure are as follows: +.TP +.I .hdr +This is a structure of type +.IR fanotify_event_info_header . +The +.I .info_type +field is set to +.BR FAN_EVENT_INFO_TYPE_MNT . +.TP +.I .mnt_id +Identifies the mount associated with the event. +.P +The fields of the .I fanotify_event_info_error structure are as follows: .TP