linux.git/fs/cachefiles/xattr.c, branch v5.17

cachefiles: Fix volume coherency attribute

2022-03-11T18:24:37+00:00

A network filesystem may set coherency data on a volume cookie, and if
given, cachefiles will store this in an xattr on the directory in the
cache corresponding to the volume.

The function that sets the xattr just stores the contents of the volume
coherency buffer directly into the xattr, with nothing added; the
checking function, on the other hand, has a cut'n'paste error whereby it
tries to interpret the xattr contents as would be the xattr on an
ordinary file (using the cachefiles_xattr struct).  This results in a
failure to match the coherency data because the buffer ends up being
shifted by 18 bytes.

Fix this by defining a structure specifically for the volume xattr and
making both the setting and checking functions use it.

Since the volume coherency doesn't work if used, take the opportunity to
insert a reserved field for future use, set it to 0 and check that it is
0.  Log mismatch through the appropriate tracepoint.

Note that this only affects cifs; 9p, afs, ceph and nfs don't use the
volume coherency data at the moment.

Fixes: 32e150037dce ("fscache, cachefiles: Store the volume coherency data")
Reported-by: Rohith Surabattula 
Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: Steve French 
cc: linux-cifs@vger.kernel.org
cc: linux-cachefs@redhat.com
Signed-off-by: Linus Torvalds

fscache, cachefiles: Store the volume coherency data

2022-01-07T13:43:03+00:00

Store the volume coherency data in an xattr and check it when we rebind the
volume.  If it doesn't match the cache volume is moved to the graveyard and
rebuilt anew.

Changes
=======
ver #4:
 - Remove a couple of debugging prints.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
Link: https://lore.kernel.org/r/163967164397.1823006.2950539849831291830.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021563138.640689.15851092065380543119.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Implement metadata/coherency data storage in xattrs

2022-01-07T13:42:24+00:00

Use an xattr on each backing file in the cache to store some metadata, such
as the content type and the coherency data.

Five content types are defined:

 (0) No content stored.

 (1) The file contains a single monolithic blob and must be all or nothing.
     This would be used for something like an AFS directory or a symlink.

 (2) The file is populated with content completely up to a point with
     nothing beyond that.

 (3) The file has a map attached and is sparsely populated.  This would be
     stored in one or more additional xattrs.

 (4) The file is dirty, being in the process of local modification and the
     contents are not necessarily represented correctly by the metadata.
     The file should be deleted if this is seen on binding.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819641320.215744.16346770087799536862.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906942248.143852.5423738045012094252.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967151734.1823006.9301249989443622576.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021550471.640689.553853918307994335.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Delete the cachefiles driver pending rewrite

2022-01-07T09:22:19+00:00

Delete the code from the cachefiles driver to make it easier to rewrite and
resubmit in a logical manner.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819577641.215744.12718114397770666596.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906883770.143852.4149714614981373410.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967076066.1823006.7175712134577687753.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021483619.640689.7586546280515844702.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Change %p in format strings to something else

2021-08-27T12:34:02+00:00

Change plain %p in format strings in cachefiles code to something more
useful, since %p is now hashed before printing and thus no longer matches
the contents of an oops register dump.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/160588476042.3465195.6837847445880367183.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/162431200692.2908479.9253374494073633778.stgit@warthog.procyon.org.uk/

xattr: handle idmapped mounts

2021-01-24T13:27:17+00:00

When interacting with extended attributes the vfs verifies that the
caller is privileged over the inode with which the extended attribute is
associated. For posix access and posix default extended attributes a uid
or gid can be stored on-disk. Let the functions handle posix extended
attributes on idmapped mounts. If the inode is accessed through an
idmapped mount we need to map it according to the mount's user
namespace. Afterwards the checks are identical to non-idmapped mounts.
This has no effect for e.g. security xattrs since they don't store uids
or gids and don't perform permission checks on them like posix acls do.

Link: https://lore.kernel.org/r/20210121131959.646623-10-christian.brauner@ubuntu.com
Cc: Christoph Hellwig 
Cc: David Howells 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Reviewed-by: James Morris 
Signed-off-by: Tycho Andersen 
Signed-off-by: Christian Brauner

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36

2019-05-24T15:27:11+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public licence as published by
  the free software foundation either version 2 of the licence or at
  your option any later version

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 114 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Reviewed-by: Kate Stewart 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520170857.552531963@linutronix.de
Signed-off-by: Greg Kroah-Hartman

cachefiles: Fix an assertion failure when trying to update a failed object

2018-11-28T13:19:20+00:00

If cachefiles gets an error other then ENOENT when trying to look up an
object in the cache (in this case, EACCES), the object state machine will
eventually transition to the DROP_OBJECT state.

This state invokes fscache_drop_object() which tries to sync the auxiliary
data with the cache (this is done lazily since commit 402cb8dda949d) on an
incomplete cache object struct.

The problem comes when cachefiles_update_object_xattr() is called to
rewrite the xattr holding the data.  There's an assertion there that the
cache object points to a dentry as we're going to update its xattr.  The
assertion trips, however, as dentry didn't get set.

Fix the problem by skipping the update in cachefiles if the object doesn't
refer to a dentry.  A better way to do it could be to skip the update from
the DROP_OBJECT state handler in fscache, but that might deny the cache the
opportunity to update intermediate state.

If this error occurs, the kernel log includes lines that look like the
following:

 CacheFiles: Lookup failed error -13
 CacheFiles:
 CacheFiles: Assertion failed
 ------------[ cut here ]------------
 kernel BUG at fs/cachefiles/xattr.c:138!
 ...
 Workqueue: fscache_object fscache_object_work_func [fscache]
 RIP: 0010:cachefiles_update_object_xattr.cold.4+0x18/0x1a [cachefiles]
 ...
 Call Trace:
  cachefiles_update_object+0xdd/0x1c0 [cachefiles]
  fscache_update_aux_data+0x23/0x30 [fscache]
  fscache_drop_object+0x18e/0x1c0 [fscache]
  fscache_object_work_func+0x74/0x2b0 [fscache]
  process_one_work+0x18d/0x340
  worker_thread+0x2e/0x390
  ? pwq_unbound_release_workfn+0xd0/0xd0
  kthread+0x112/0x130
  ? kthread_bind+0x30/0x30
  ret_from_fork+0x35/0x40

Note that there are actually two issues here: (1) EACCES happened on a
cache object and (2) an oops occurred.  I think that the second is a
consequence of the first (it certainly looks like it ought to be).  This
patch only deals with the second.

Fixes: 402cb8dda949 ("fscache: Attach the index key and aux data to the cookie")
Reported-by: Zhibin Li 
Signed-off-by: David Howells

fscache: Pass object size in rather than calling back for it

2018-04-06T13:05:14+00:00

Pass the object size in to fscache_acquire_cookie() and
fscache_write_page() rather than the netfs providing a callback by which it
can be received.  This makes it easier to update the size of the object
when a new page is written that extends the object.

The current object size is also passed by fscache to the check_aux
function, obviating the need to store it in the aux data.

Signed-off-by: David Howells 
Acked-by: Anna Schumaker 
Tested-by: Steve Dickson

fscache: Attach the index key and aux data to the cookie

2018-04-04T12:41:28+00:00

Attach copies of the index key and auxiliary data to the fscache cookie so
that:

 (1) The callbacks to the netfs for this stuff can be eliminated.  This
     can simplify things in the cache as the information is still
     available, even after the cache has relinquished the cookie.

 (2) Simplifies the locking requirements of accessing the information as we
     don't have to worry about the netfs object going away on us.

 (3) The cache can do lazy updating of the coherency information on disk.
     As long as the cache is flushed before reboot/poweroff, there's no
     need to update the coherency info on disk every time it changes.

 (4) Cookies can be hashed or put in a tree as the index key is easily
     available.  This allows:

     (a) Checks for duplicate cookies can be made at the top fscache layer
     	 rather than down in the bowels of the cache backend.

     (b) Caching can be added to a netfs object that has a cookie if the
     	 cache is brought online after the netfs object is allocated.

A certain amount of space is made in the cookie for inline copies of the
data, but if it won't fit there, extra memory will be allocated for it.

The downside of this is that live cache operation requires more memory.

Signed-off-by: David Howells 
Acked-by: Anna Schumaker 
Tested-by: Steve Dickson