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  1. Aug 31, 2022
    • Christian Brauner's avatar
      ovl: use vfs_set_acl_prepare() · 7e1401ac
      Christian Brauner authored 
      

The posix_acl_from_xattr() helper should mainly be used in
i_op->get_acl() handlers. It translates from the uapi struct into the
kernel internal POSIX ACL representation and doesn't care about mount
idmappings.

Use the vfs_set_acl_prepare() helper to generate a kernel internal POSIX
ACL representation in struct posix_acl format taking care to map from
the mount idmapping into the filesystem's idmapping.

The returned struct posix_acl is in the correct format to be cached by
the VFS or passed to the filesystem's i_op->set_acl() method to write to
the backing store.

Signed-off-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: default avatarSeth Forshee (DigitalOcean) <sforshee@kernel.org>
      7e1401ac
    • Christian Brauner's avatar
      acl: move idmapping handling into posix_acl_xattr_set() · 52edb408
      Christian Brauner authored 
      The uapi POSIX ACL struct passed through the value argument during
setxattr() contains {g,u}id values encoded via ACL_{GROUP,USER} entries
that should actually be stored in the form of k{g,u}id_t (See [1] for a
long explanation of the issue.).

In 0c5fd887 ("acl: move idmapped mount fixup into vfs_{g,s}etxattr()")
we took the mount's idmapping into account in order to let overlayfs
handle POSIX ACLs on idmapped layers correctly. The fixup is currently
performed directly in vfs_setxattr() which piles on top of the earlier
hackiness by handling the mount's idmapping and stuff the vfs{g,u}id_t
values into the uapi struct as well. While that is all correct and works
fine it's just ugly.

Now that we have introduced vfs_make_posix_acl() earlier move handling
idmapped mounts out of vfs_setxattr() and into the POSIX ACL handler
where it belongs.

Note that we also need to call vfs_make_posix_acl() for EVM which
interpretes POSIX ACLs during security_inode_setxattr(). Leave them a
longer comment for future reference.

All filesystems that support idmapped mounts via FS_ALLOW_IDMAP use the
standard POSIX ACL xattr handlers and are covered by this change. This
includes overlayfs which simply calls vfs_{g,s}etxattr().

The following filesystems use custom POSIX ACL xattr handlers: 9p, cifs,
ecryptfs, and ntfs3 (and overlayfs but we've covered that in the paragraph
above) and none of them support idmapped mounts yet.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org/

 [1]
Signed-off-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: default avatarSeth Forshee (DigitalOcean) <sforshee@kernel.org>
      52edb408
    • Christian Brauner's avatar
      acl: add vfs_set_acl_prepare() · 6b70fe06
      Christian Brauner authored 
      Various filesystems store POSIX ACLs on the backing store in their uapi
format. Such filesystems need to translate from the uapi POSIX ACL
format into the VFS format during i_op->get_acl(). The VFS provides the
posix_acl_from_xattr() helper for this task.

But the usage of posix_acl_from_xattr() is currently ambiguous. It is
intended to transform from a uapi POSIX ACL  to the VFS represenation.
For example, when retrieving POSIX ACLs for permission checking during
lookup or when calling getxattr() to retrieve system.posix_acl_{access,default}.

Calling posix_acl_from_xattr() during i_op->get_acl() will map the raw
{g,u}id values stored as ACL_{GROUP,USER} entries in the uapi POSIX ACL
format into k{g,u}id_t in the filesystem's idmapping and return a struct
posix_acl ready to be returned to the VFS for caching and to perform
permission checks on.

However, posix_acl_from_xattr() is also called during setxattr() for all
filesystems that rely on VFS provides posix_acl_{access,default}_xattr_handler.
The posix_acl_xattr_set() handler which is used for the ->set() method
of posix_acl_{access,default}_xattr_handler uses posix_acl_from_xattr()
to translate from the uapi POSIX ACL format to the VFS format so that it
can be passed to the i_op->set_acl() handler of the filesystem or for
direct caching in case no i_op->set_acl() handler is defined.

During setxattr() the {g,u}id values stored as ACL_{GROUP,USER} entries
in the uapi POSIX ACL format aren't raw {g,u}id values that need to be
mapped according to the filesystem's idmapping. Instead they are {g,u}id
values in the caller's idmapping which have been generated during
posix_acl_fix_xattr_from_user(). In other words, they are k{g,u}id_t
which are passed as raw {g,u}id values abusing the uapi POSIX ACL format
(Please note that this type safety violation has existed since the
introduction of k{g,u}id_t. Please see [1] for more details.).

So when posix_acl_from_xattr() is called in posix_acl_xattr_set() the
filesystem idmapping is completely irrelevant. Instead, we abuse the
initial idmapping to recover the k{g,u}id_t base on the value stored in
raw {g,u}id as ACL_{GROUP,USER} in the uapi POSIX ACL format.

We need to clearly distinguish betweeen these two operations as it is
really easy to confuse for filesystems as can be seen in ntfs3.

In order to do this we factor out make_posix_acl() which takes callbacks
allowing callers to pass dedicated methods to generate the correct
k{g,u}id_t. This is just an internal static helper which is not exposed
to any filesystems but it neatly encapsulates the basic logic of walking
through a uapi POSIX ACL and returning an allocated VFS POSIX ACL with
the correct k{g,u}id_t values.

The posix_acl_from_xattr() helper can then be implemented as a simple
call to make_posix_acl() with callbacks that generate the correct
k{g,u}id_t from the raw {g,u}id values in ACL_{GROUP,USER} entries in
the uapi POSIX ACL format as read from the backing store.

For setxattr() we add a new helper vfs_set_acl_prepare() which has
callbacks to map the POSIX ACLs from the uapi format with the k{g,u}id_t
values stored in raw {g,u}id format in ACL_{GROUP,USER} entries into the
correct k{g,u}id_t values in the filesystem idmapping. In contrast to
posix_acl_from_xattr() the vfs_set_acl_prepare() helper needs to take
the mount idmapping into account. The differences are explained in more
detail in the kernel doc for the new functions.

In follow up patches we will remove all abuses of posix_acl_from_xattr()
for setxattr() operations and replace it with calls to vfs_set_acl_prepare().

The new vfs_set_acl_prepare() helper allows us to deal with the
ambiguity in how the POSI ACL uapi struct stores {g,u}id values
depending on whether this is a getxattr() or setxattr() operation.

This also allows us to remove the posix_acl_setxattr_idmapped_mnt()
helper reducing the abuse of the POSIX ACL uapi format to pass values
that should be distinct types in {g,u}id values stored as
ACL_{GROUP,USER} entries.

The removal of posix_acl_setxattr_idmapped_mnt() in turn allows us to
re-constify the value parameter of vfs_setxattr() which in turn allows
us to avoid the nasty cast from a const void pointer to a non-const void
pointer on ovl_do_setxattr().

Ultimately, the plan is to get rid of the type violations completely and
never pass the values from k{g,u}id_t as raw {g,u}id in ACL_{GROUP,USER}
entries in uapi POSIX ACL format. But that's a longer way to go and this
is a preparatory step.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org

 [1]
Co-Developed-by: default avatarSeth Forshee <sforshee@digitalocean.com>
Signed-off-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
      6b70fe06
    • Christian Brauner's avatar
      acl: return EOPNOTSUPP in posix_acl_fix_xattr_common() · 985a6d0b
      Christian Brauner authored 
      Return EOPNOTSUPP when the POSIX ACL version doesn't match and zero if
there are no entries. This will allow us to reuse the helper in
posix_acl_from_xattr(). This change will have no user visible effects.

Fixes: 0c5fd887

 ("acl: move idmapped mount fixup into vfs_{g,s}etxattr()")
Signed-off-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: default avatarSeth Forshee (DigitalOcean) <sforshee@kernel.org&gt;>
      985a6d0b
    • Christian Brauner's avatar
      ntfs3: rework xattr handlers and switch to POSIX ACL VFS helpers · a26aa123
      Christian Brauner authored 
      The xattr code in ntfs3 is currently a bit confused. For example, it
defines a POSIX ACL i_op->set_acl() method but instead of relying on the
generic POSIX ACL VFS helpers it defines its own set of xattr helpers
with the consequence that i_op->set_acl() is currently dead code.

Switch ntfs3 to rely on the VFS POSIX ACL xattr handlers. Also remove
i_op->{g,s}et_acl() methods from symlink inode operations. Symlinks
don't support xattrs.

This is a preliminary change for the following patches which move
handling idmapped mounts directly in posix_acl_xattr_set().

This survives POSIX ACL xfstests.

Fixes: be71b5cb

 ("fs/ntfs3: Add attrib operations")
Signed-off-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: default avatarSeth Forshee (DigitalOcean) <sforshee@kernel.org&gt;>
      a26aa123
  3. Aug 29, 2022
  5. Aug 28, 2022
  7. Aug 27, 2022
    • Zhengjun Xing's avatar
      perf stat: Capitalize topdown metrics' names · 48648548
      Zhengjun Xing authored 
      

Capitalize topdown metrics' names to follow the intel SDM.

Before:

 # ./perf stat -a  sleep 1

 Performance counter stats for 'system wide':

        228,094.05 msec cpu-clock                        #  225.026 CPUs utilized
               842      context-switches                 #    3.691 /sec
               224      cpu-migrations                   #    0.982 /sec
                70      page-faults                      #    0.307 /sec
        23,164,105      cycles                           #    0.000 GHz
        29,403,446      instructions                     #    1.27  insn per cycle
         5,268,185      branches                         #   23.097 K/sec
            33,239      branch-misses                    #    0.63% of all branches
       136,248,990      slots                            #  597.337 K/sec
        32,976,450      topdown-retiring                 #     24.2% retiring
         4,651,918      topdown-bad-spec                 #      3.4% bad speculation
        26,148,695      topdown-fe-bound                 #     19.2% frontend bound
        72,515,776      topdown-be-bound                 #     53.2% backend bound
         6,008,540      topdown-heavy-ops                #      4.4% heavy operations       #     19.8% light operations
         3,934,049      topdown-br-mispredict            #      2.9% branch mispredict      #      0.5% machine clears
        16,655,439      topdown-fetch-lat                #     12.2% fetch latency          #      7.0% fetch bandwidth
        41,635,972      topdown-mem-bound                #     30.5% memory bound           #     22.7% Core bound

       1.013634593 seconds time elapsed

After:

 # ./perf stat -a  sleep 1

 Performance counter stats for 'system wide':

        228,081.94 msec cpu-clock                        #  225.003 CPUs utilized
               824      context-switches                 #    3.613 /sec
               224      cpu-migrations                   #    0.982 /sec
                67      page-faults                      #    0.294 /sec
        22,647,423      cycles                           #    0.000 GHz
        28,870,551      instructions                     #    1.27  insn per cycle
         5,167,099      branches                         #   22.655 K/sec
            32,383      branch-misses                    #    0.63% of all branches
       133,411,074      slots                            #  584.926 K/sec
        32,352,607      topdown-retiring                 #     24.3% Retiring
         4,456,977      topdown-bad-spec                 #      3.3% Bad Speculation
        25,626,487      topdown-fe-bound                 #     19.2% Frontend Bound
        70,955,316      topdown-be-bound                 #     53.2% Backend Bound
         5,834,844      topdown-heavy-ops                #      4.4% Heavy Operations       #     19.9% Light Operations
         3,738,781      topdown-br-mispredict            #      2.8% Branch Mispredict      #      0.5% Machine Clears
        16,286,803      topdown-fetch-lat                #     12.2% Fetch Latency          #      7.0% Fetch Bandwidth
        40,802,069      topdown-mem-bound                #     30.6% Memory Bound           #     22.6% Core Bound

       1.013683125 seconds time elapsed

Reviewed-by: default avatarKan Liang <kan.liang@linux.intel.com>
Signed-off-by: default avatarXing Zhengjun <zhengjun.xing@linux.intel.com>
Acked-by: default avatarIan Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220825015458.3252239-1-zhengjun.xing@linux.intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      48648548
    • Kan Liang's avatar
      perf docs: Update the documentation for the save_type filter · 3126204c
      Kan Liang authored 
      

Update the documentation to reflect the kernel changes.

Signed-off-by: default avatarKan Liang <kan.liang@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20220816125612.2042397-2-kan.liang@linux.intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      3126204c