Hi Josef, On Tue, Jul 09, 2024 at 02:31:22PM GMT, Josef Bacik wrote: > Add some documentation on the new statmount syscall. > > Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx> I've applied the patch, with some tweaks. <https://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git/commit/?h=contrib&id=1e607c20633d839d9241da50071d508ef617f878> Have a lovely day! Alex diff --git i/man/man2/statmount.2 w/man/man2/statmount.2 index 2ae1f1bc3..4b54a6c85 100644 --- i/man/man2/statmount.2 +++ w/man/man2/statmount.2 @@ -14,40 +14,42 @@ .SH SYNOPSIS .BR "#include <linux/mount.h>" " /* Definition of STATMOUNT_* constants */" .B #include <unistd.h> .P -.BI "int syscall(SYS_statmount, struct mnt_id_req * " req , -.BI " struct statmount * " smbuf ", size_t " bufsize , +.BI "int syscall(SYS_statmount, struct mnt_id_req *" req , +.BI " struct statmount *" smbuf ", size_t " bufsize , .BI " unsigned long " flags ); .P .B #include <linux/mount.h> +.fi .P +.EX .B struct mnt_id_req { -.BR " __u32 size;" " /* sizeof(struct mnt_id_req) */" -.BR " __u64 mnt_id;" " /* The mnt_id being queried */" -.BR " __u64 param;" " /* An ORed combination of the STATMOUNT_ constants */" +.BR " __u32 size;" " /* sizeof(struct mnt_id_req) */" +.BR " __u64 mnt_id;" " /* The mnt_id being queried */" +.BR " __u64 param;" " /* An ORed combination of the STATMOUNT_ constants */" .B }; .P .B struct statmount { -.B " __u32 size;" -.B " __u64 mask;" -.B " __u32 sb_dev_major;" -.B " __u32 sb_dev_minor;" -.B " __u64 sb_magic;" -.B " __u32 sb_flags;" -.B " __u32 fs_type;" -.B " __u64 mnt_id;" -.B " __u64 mnt_parent_id;" -.B " __u32 mnt_id_old;" -.B " __u32 mnt_parent_id_old;" -.B " __u64 mnt_attr;" -.B " __u64 mnt_propagation;" -.B " __u64 mnt_peer_group;" -.B " __u64 mnt_master;" -.B " __u64 propagate_from;" -.B " __u32 mnt_root;" -.B " __u32 mnt_point;" -.B " char str[];" +.B " __u32 size;" +.B " __u64 mask;" +.B " __u32 sb_dev_major;" +.B " __u32 sb_dev_minor;" +.B " __u64 sb_magic;" +.B " __u32 sb_flags;" +.B " __u32 fs_type;" +.B " __u64 mnt_id;" +.B " __u64 mnt_parent_id;" +.B " __u32 mnt_id_old;" +.B " __u32 mnt_parent_id_old;" +.B " __u64 mnt_attr;" +.B " __u64 mnt_propagation;" +.B " __u64 mnt_peer_group;" +.B " __u64 mnt_master;" +.B " __u64 propagate_from;" +.B " __u32 mnt_root;" +.B " __u32 mnt_point;" +.B " char str[];" .B }; -.fi +.EE .P .IR Note : glibc provides no wrapper for @@ -117,7 +119,7 @@ .SS The mnt_id_req structure .I statmount.mask field. Therefore, -.I "do not" +.I do not simply set .I req.param to > --- > man/man2/statmount.2 | 281 +++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 281 insertions(+) > create mode 100644 man/man2/statmount.2 > > diff --git a/man/man2/statmount.2 b/man/man2/statmount.2 > new file mode 100644 > index 000000000..2ae1f1bc3 > --- /dev/null > +++ b/man/man2/statmount.2 > @@ -0,0 +1,281 @@ > +'\" t > +.\" Copyright (c) 2024 Josef Bacik <josef@xxxxxxxxxxxxxx> > +.\" > +.\" SPDX-License-Identifier: Linux-man-pages-copyleft > +.\" > +.TH statmount 2 (date) "Linux man-pages (unreleased)" > +.SH NAME > +statmount \- get a mount status > +.SH LIBRARY > +Standard C library > +.RI ( libc ", " \-lc ) > +.SH SYNOPSIS > +.nf > +.BR "#include <linux/mount.h>" " /* Definition of STATMOUNT_* constants */" > +.B #include <unistd.h> > +.P > +.BI "int syscall(SYS_statmount, struct mnt_id_req * " req , > +.BI " struct statmount * " smbuf ", size_t " bufsize , > +.BI " unsigned long " flags ); > +.P > +.B #include <linux/mount.h> > +.P > +.B struct mnt_id_req { > +.BR " __u32 size;" " /* sizeof(struct mnt_id_req) */" > +.BR " __u64 mnt_id;" " /* The mnt_id being queried */" > +.BR " __u64 param;" " /* An ORed combination of the STATMOUNT_ constants */" > +.B }; > +.P > +.B struct statmount { > +.B " __u32 size;" > +.B " __u64 mask;" > +.B " __u32 sb_dev_major;" > +.B " __u32 sb_dev_minor;" > +.B " __u64 sb_magic;" > +.B " __u32 sb_flags;" > +.B " __u32 fs_type;" > +.B " __u64 mnt_id;" > +.B " __u64 mnt_parent_id;" > +.B " __u32 mnt_id_old;" > +.B " __u32 mnt_parent_id_old;" > +.B " __u64 mnt_attr;" > +.B " __u64 mnt_propagation;" > +.B " __u64 mnt_peer_group;" > +.B " __u64 mnt_master;" > +.B " __u64 propagate_from;" > +.B " __u32 mnt_root;" > +.B " __u32 mnt_point;" > +.B " char str[];" > +.B }; > +.fi > +.P > +.IR Note : > +glibc provides no wrapper for > +.BR statmount (), > +necessitating the use of > +.BR syscall (2). > +.SH DESCRIPTION > +To access a mount's status, > +the caller must have CAP_SYS_ADMIN in the user namespace. > +.P > +This function returns information about a mount, > +storing it in the buffer pointed to by > +.IR smbuf . > +The returned buffer is a > +.I struct statmount > +which is of size > +.I bufsize > +with the fields filled in as described below. > +.P > +(Note that reserved space and padding is omitted.) > +.SS The mnt_id_req structure > +.I req.size > +is used by the kernel to determine which > +.I struct\~mnt_id_req > +is being passed in; > +it should always be set to > +.IR sizeof(struct\~mnt_id_req) . > +.P > +.I req.mnt_id > +can be obtained from either > +.BR statx (2) > +using > +.B STATX_MNT_ID_UNIQUE > +or from > +.BR listmount (2) > +and is used as the identifier to query the status of the desired mount point. > +.P > +.I req.param > +is used to tell the kernel which fields the caller is interested in. > +It is an ORed combination of the following constants > +.P > +.in +4n > +.TS > +lB l. > +STATMOUNT_SB_BASIC /* Want/got sb_* */ > +STATMOUNT_MNT_BASIC /* Want/got mnt_* */ > +STATMOUNT_PROPAGATE_FROM /* Want/got propagate_from */ > +STATMOUNT_MNT_ROOT /* Want/got mnt_root */ > +STATMOUNT_MNT_POINT /* Want/got mnt_point */ > +STATMOUNT_FS_TYPE /* Want/got fs_type */ > +.TE > +.in > +.P > +In general, > +the kernel does > +.I not > +reject values in > +.I req.param > +other than the above. > +(For an exception, > +see > +.B EINVAL > +in errors.) > +Instead, > +it simply informs the caller which values are supported > +by this kernel and filesystem via the > +.I statmount.mask > +field. > +Therefore, > +.I "do not" > +simply set > +.I req.param > +to > +.B UINT_MAX > +(all bits set), > +as one or more bits may, > +in the future, > +be used to specify an extension to the buffer. > +.SS The returned information > +The status information for the target mount is returned in the > +.I statmount > +structure pointed to by > +.IR smbuf . > +.P > +The fields in the > +.I statmount > +structure are: > +.TP > +.I smbuf.size > +The size of the returned > +.I smbuf > +structure, > +including any of the strings fields that were filled. > +.TP > +.I smbuf.mask > +The ORed combination of > +.BI STATMOUNT_ * > +flags indicating which fields were filled in and thus valid. > +The kernel may return fields that weren't requested, > +and may fail to return fields that were requested, > +depending on what the backing file system and kernel supports. > +In either case, > +.I req.param > +will not be equal to > +.IR mask . > +.TP > +.I smbuf.sb_dev_major > +.TQ > +.I smbuf.sb_dev_minor > +The device that is mounted at this mount point. > +.TP > +.I smbuf.sb_magic > +The file system specific super block magic. > +.TP > +.I smbuf.sb_flags > +The flags that are set on the super block, > +an ORed combination of > +.BR SB_RDONLY , > +.BR SB_SYNCHRONOUS , > +.BR SB_DIRSYNC , > +.BR SB_LAZYTIME . > +.TP > +.I smbuf.fs_type > +The offset to the location in the > +.I smbuf.str > +buffer that contains the string representation of the mounted file system. > +It is a null-terminated string. > +.TP > +.I smbuf.mnt_id > +The unique mount ID of the mount. > +.TP > +.I smbuf.mnt_parent_id > +The unique mount ID of the parent mount point of this mount. > +If this is the root mount point then > +.IR smbuf.mnt_id\~==\~smbuf.parent_mount_id . > +.TP > +.I smbuf.mnt_id_old > +This corresponds to the mount ID that is exported by > +.IR /proc/ pid /mountinfo . > +.TP > +.I smbuf.mnt_parent_id_old > +This corresponds to the parent mount ID that is exported by > +.IR /proc/ pid /mountinfo . > +.TP > +.I smbuf.mnt_attr > +The > +.BI MOUNT_ATTR_ * > +flags set on this mount point. > +.TP > +.I smbuf.mnt_propagation > +The mount propagation flags, > +which can be one of > +.BR MS_SHARED , > +.BR MS_SLAVE , > +.BR MS_PRIVATE , > +.BR MS_UNBINDABLE . > +.TP > +.I smbuf.mnt_peer_group > +The ID of the shared peer group. > +.TP > +.I smbuf.mnt_master > +The mount point receives its propagation from this mount ID. > +.TP > +.I smbuf.propagate_from > +The ID from the namespace we propagated from. > +.TP > +.I smbuf.mnt_root > +The offset to the location in the > +.I smbuf.str > +buffer that contains the string representation of the mount > +relative to the root of the file system. > +It is a null-terminated string. > +.TP > +.I smbuf.mnt_point > +The offset to the location in the > +.I smbuf.str > +buffer that contains the string representation of the mount > +relative to the current root (ie if you are in a > +.BR chroot ). > +It is a null-terminated string. > +.SH RETURN VALUE > +On success, zero is returned. > +On error, \-1 is returned, and > +.I errno > +is set to indicate the error. > +.SH ERRORS > +.TP > +.B EPERM > +Permission is denied for accessing this mount. > +.TP > +.B EFAULT > +.I req > +or > +.I smbuf > +points to a location outside the process's accessible > +address space. > +.TP > +.B EINVAL > +Invalid flag specified in > +.IR flags . > +.TP > +.B EINVAL > +.I req > +is of insufficient size to be utilized. > +.TP > +.B E2BIG > +.I req > +is too large. > +.TP > +.B EOVERFLOW > +The size of > +.I smbuf > +is too small to contain either the > +.IR smbuf.fs_type , > +.IR smbuf.mnt_root , > +or > +.IR smbuf.mnt_point . > +Allocate a larger buffer and retry the call. > +.TP > +.B ENOENT > +The specified > +.I req.mnt_id > +doesn't exist. > +.TP > +.B ENOMEM > +Out of memory (i.e., kernel memory). > +.SH STANDARDS > +Linux. > +.SH SEE ALSO > +.BR listmount (2), > +.BR statx (2) > -- > 2.43.0 > > -- <https://www.alejandro-colomar.es/>
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