Documentation/filesystems/idmappings.rst

14 An idmapping is essentially a translation of a range of ids into another or the
37 idmapping is an order isomorphism from ``U`` into ``K``. So ``U`` and ``K`` are
50 dealing with subsets we can embed idmappings into each other, i.e. we can
126 of userspace ids into a range of kernel ids::
174 immediately translated into a kernel id according to the idmapping associated
212 then translate ``k11000`` into a userspace id in the second idmapping using the
215  /* Map the kernel id up into a userspace id in the second idmapping. */
221  /* Map the userspace id down into a kernel id in the second idmapping. */
224  /* Map the kernel id up into a userspace id in the first idmapping. */
233 into a kernel id according to the idmapping associated with the filesystem.
262 kernel id in the first idmapping into a kernel id in the second idmapping we
265 1. Map the kernel id up into a userspace id in the first idmapping::
267     /* Map the kernel id up into a userspace id in the first idmapping. */
270 2. Map the userspace id down into a kernel id in the second idmapping::
272     /* Map the userspace id down into a kernel id in the second idmapping. */
286 1. Map the kernel id up into a userspace id in the second idmapping::
288     /* Map the kernel id up into a userspace id in the second idmapping. */
291 2. Map the userspace id down into a kernel id in the first idmapping::
293     /* Map the userspace id down into a kernel id in the first idmapping. */
308  /* Map the userspace id down into a kernel id in the first idmapping. */
311  /* INVALID: Map the kernel id down into a kernel id in the second idmapping. */
317  /* Map the kernel id up into a userspace id in the first idmapping. */
320  /* INVALID: Map the userspace id up into a userspace id in the second idmapping. */
335  /* Map the userspace id down into a kernel id. */
338  /* Map the kernel id up into a userspace id. */
341 We will take an abbreviated look into how idmappings figure into creating
343 VFS has already completed path lookup right before it calls into the filesystem
357 1. Map the caller's userspace ids down into kernel ids in the caller's
366 the kernel id back up into a userspace id when writing to disk.
373 kernel maps the caller's userspace id down into a kernel id according to the
400 1. Map the caller's userspace ids into kernel ids in the caller's idmapping::
425 1. Map the caller's userspace ids down into kernel ids in the caller's
436 successfully mapped down into kernel ids in the caller's idmapping the kernel
453 1. Map the caller's userspace ids down into kernel ids in the caller's
476 kernel ids map up into valid userspace ids in the caller's idmapping
498 1. Map the userspace id on disk down into a kernel id in the filesystem's
503 2. Map the kernel id up into a userspace id in the caller's idmapping::
524 1. Map the userspace id on disk down into a kernel id in the filesystem's
529 2. Map the kernel id up into a userspace id in the caller's idmapping::
543 1. Map the userspace id on disk down into a kernel id in the filesystem's
548 2. Map the kernel id up into a userspace id in the caller's idmapping::
577 files below it can be crossmapped from the filesystem's into the container's
674 Thus, we are turning the ``vfsuid_t`` or ``vfsgid_t`` into a global ``kuid_t``
706   The ``i_*id_into_vfs*id()`` functions translate filesystem's kernel ids into
709    /* Map the filesystem's kernel id up into a userspace id in the filesystem's idmapping. */
717   The ``mapped_fs*id()`` functions translate the caller's kernel ids into
721    /* Map the caller's VFS id up into a userspace id in the mount's idmapping. */
724    /* Map the mount's userspace id down into a kernel id in the filesystem's idmapping. */
748 id into a VFS id in the mount's idmapping::
751    /* Map the filesystem's kernel id up into a userspace id. */
754    /* Map the filesystem's userspace id down into a VFS id in the mount's idmapping. */
758 VFS id in the mount's idmapping into a userspace id in the caller's
774 first call ``mapped_fs*id()`` thereby translating the caller's kernel id into
778     /* Map the caller's kernel id up into a userspace id in the mount's idmapping. */
781     /* Map the mount's userspace id down into a kernel id in the filesystem's idmapping. */
784 When finally writing to disk the kernel will then map ``v21000`` up into a
810 1. Map the caller's userspace ids into kernel ids in the caller's idmapping::
814 2. Translate the caller's VFS id into a kernel id in the filesystem's
818       /* Map the VFS id up into a userspace id in the mount's idmapping. */
821       /* Map the userspace id down into a kernel id in the filesystem's idmapping. */
843 1. Map the caller's userspace ids into kernel ids in the caller's idmapping::
847 2. Translate the caller's VFS id into a kernel id in the filesystem's
851        /* Map the VFS id up into a userspace id in the mount's idmapping. */
854        /* Map the userspace id down into a kernel id in the filesystem's idmapping. */
877 1. Map the userspace id on disk down into a kernel id in the filesystem's
882 2. Translate the kernel id into a VFS id in the mount's idmapping::
885       /* Map the kernel id up into a userspace id in the filesystem's idmapping. */
888       /* Map the userspace id down into a VFS id in the mounts's idmapping. */
891 3. Map the VFS id up into a userspace id in the caller's idmapping::
897 idmapping. With the idmapped mount in place it now can be crossmapped into the
914 1. Map the userspace id on disk down into a kernel id in the filesystem's
919 2. Translate the kernel id into a VFS id in the mount's idmapping::
922       /* Map the kernel id up into a userspace id in the filesystem's idmapping. */
925       /* Map the userspace id down into a VFS id in the mounts's idmapping. */
928 3. Map the VFS id up into a userspace id in the caller's idmapping::
934 idmapping. With the idmapped mount in place it now can be crossmapped into the
983 1. Map the caller's userspace ids into kernel ids in the caller's idmapping::
987 2. Translate the caller's VFS id into a kernel id in the filesystem's
991       /* Map the VFS id up into a userspace id in the mount's idmapping. */
994       /* Map the userspace id down into a kernel id in the filesystem's idmapping. */
1014 1. Map the userspace id on disk down into a kernel id in the filesystem's
1019 2. Translate the kernel id into a VFS id in the mount's idmapping::
1022       /* Map the kernel id up into a userspace id in the filesystem's idmapping. */
1025       /* Map the userspace id down into a VFS id in the mounts's idmapping. */
1028 3. Map the VFS id up into a userspace id in the caller's idmapping::