Add a way to query attributes of a single mount instead of having to parse the complete /proc/$PID/mountinfo, which might be huge. Lookup the mount the new 64bit mount ID. If a mount needs to be queried based on path, then statx(2) can be used to first query the mount ID belonging to the path. Design is based on a suggestion by Linus: "So I'd suggest something that is very much like "statfsat()", which gets a buffer and a length, and returns an extended "struct statfs" *AND* just a string description at the end." The interface closely mimics that of statx. Handle ASCII attributes by appending after the end of the structure (as per above suggestion). Pointers to strings are stored in u64 members to make the structure the same regardless of pointer size. Strings are nul terminated.
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| @@ -138,4 +138,57 @@ struct mount_attr { · 137 unmodified lines | ||
| 138 | 138 | /* List of all mount_attr versions. */ |
| 139 | 139 | #define MOUNT_ATTR_SIZE_VER0 32 /* sizeof first published struct */ |
| 140 | 140 | |
| 141 | + | |
| 142 | +/* | |
| 143 | + * Structure for getting mount/superblock/filesystem info with statmount(2). | |
| 144 | + * | |
| 145 | + * The interface is similar to statx(2): individual fields or groups can be | |
| 146 | + * selected with the @mask argument of statmount(). Kernel will set the @mask | |
| 147 | + * field according to the supported fields. | |
| 148 | + * | |
| 149 | + * If string fields are selected, then the caller needs to pass a buffer that | |
| 150 | + * has space after the fixed part of the structure. Nul terminated strings are | |
| 151 | + * copied there and offsets relative to @str are stored in the relevant fields. | |
| 152 | + * If the buffer is too small, then EOVERFLOW is returned. The actually used | |
| 153 | + * size is returned in @size. | |
| 154 | + */ | |
| 155 | +struct statmount { | |
| 156 | + __u32 size; /* Total size, including strings */ | |
| 157 | + __u32 __spare1; | |
| 158 | + __u64 mask; /* What results were written */ | |
| 159 | + __u32 sb_dev_major; /* Device ID */ | |
| 160 | + __u32 sb_dev_minor; | |
| 161 | + __u64 sb_magic; /* ..._SUPER_MAGIC */ | |
| 162 | + __u32 sb_flags; /* SB_{RDONLY,SYNCHRONOUS,DIRSYNC,LAZYTIME} */ | |
| 163 | + __u32 fs_type; /* [str] Filesystem type */ | |
| 164 | + __u64 mnt_id; /* Unique ID of mount */ | |
| 165 | + __u64 mnt_parent_id; /* Unique ID of parent (for root == mnt_id) */ | |
| 166 | + __u32 mnt_id_old; /* Reused IDs used in proc/.../mountinfo */ | |
| 167 | + __u32 mnt_parent_id_old; | |
| 168 | + __u64 mnt_attr; /* MOUNT_ATTR_... */ | |
| 169 | + __u64 mnt_propagation; /* MS_{SHARED,SLAVE,PRIVATE,UNBINDABLE} */ | |
| 170 | + __u64 mnt_peer_group; /* ID of shared peer group */ | |
| 171 | + __u64 mnt_master; /* Mount receives propagation from this ID */ | |
| 172 | + __u64 propagate_from; /* Propagation from in current namespace */ | |
| 173 | + __u32 mnt_root; /* [str] Root of mount relative to root of fs */ | |
| 174 | + __u32 mnt_point; /* [str] Mountpoint relative to current root */ | |
| 175 | + __u64 __spare2[50]; | |
| 176 | + char str[]; /* Variable size part containing strings */ | |
| 177 | +}; | |
| 178 | + | |
| 179 | +struct mnt_id_req { | |
| 180 | + __u64 mnt_id; | |
| 181 | + __u64 request_mask; | |
| 182 | +}; | |
| 183 | + | |
| 184 | +/* | |
| 185 | + * @mask bits for statmount(2) | |
| 186 | + */ | |
| 187 | +#define STATMOUNT_SB_BASIC 0x00000001U /* Want/got sb_... */ | |
| 188 | +#define STATMOUNT_MNT_BASIC 0x00000002U /* Want/got mnt_... */ | |
| 189 | +#define STATMOUNT_PROPAGATE_FROM 0x00000004U /* Want/got propagate_from */ | |
| 190 | +#define STATMOUNT_MNT_ROOT 0x00000008U /* Want/got mnt_root */ | |
| 191 | +#define STATMOUNT_MNT_POINT 0x00000010U /* Want/got mnt_point */ | |
| 192 | +#define STATMOUNT_FS_TYPE 0x00000020U /* Want/got fs_type */ | |
| 193 | + | |
| 141 | 194 | #endif /* _UAPI_LINUX_MOUNT_H */ |