linux-stable.git/fs/afs, branch linux-5.17.y

afs: Fix infinite loop found by xfstest generic/676

2022-06-14T16:41:25+00:00

[ Upstream commit 17eabd42560f4636648ad65ba5b20228071e2363 ]

In AFS, a directory is handled as a file that the client downloads and
parses locally for the purposes of performing lookup and getdents
operations.  The in-kernel afs filesystem has a number of functions that
do this.

A directory file is arranged as a series of 2K blocks divided into
32-byte slots, where a directory entry occupies one or more slots, plus
each block starts with one or more metadata blocks.

When parsing a block, if the last slots are occupied by a dirent that
occupies more than a single slot and the file position points at a slot
that's not the initial one, the logic in afs_dir_iterate_block() that
skips over it won't advance the file pointer to the end of it.  This
will cause an infinite loop in getdents() as it will keep retrying that
block and failing to advance beyond the final entry.

Fix this by advancing the file pointer if the next entry will be beyond
it when we skip a block.

This was found by the generic/676 xfstest but can also be triggered with
something like:

	~/xfstests-dev/src/t_readdir_3 /xfstest.test/z 4000 1

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: David Howells 
Reviewed-by: Marc Dionne 
Tested-by: Marc Dionne 
cc: linux-afs@lists.infradead.org
Link: http://lore.kernel.org/r/165391973497.110268.2939296942213894166.stgit@warthog.procyon.org.uk/
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

afs: Adjust ACK interpretation to try and cope with NAT

2022-06-09T08:25:30+00:00

[ Upstream commit adc9613ff66c26ebaff9814973181ac178beb90b ]

If a client's address changes, say if it is NAT'd, this can disrupt an in
progress operation.  For most operations, this is not much of a problem,
but StoreData can be different as some servers modify the target file as
the data comes in, so if a store request is disrupted, the file can get
corrupted on the server.

The problem is that the server doesn't recognise packets that come after
the change of address as belonging to the original client and will bounce
them, either by sending an OUT_OF_SEQUENCE ACK to the apparent new call if
the packet number falls within the initial sequence number window of a call
or by sending an EXCEEDS_WINDOW ACK if it falls outside and then aborting
it.  In both cases, firstPacket will be 1 and previousPacket will be 0 in
the ACK information.

Fix this by the following means:

 (1) If a client call receives an EXCEEDS_WINDOW ACK with firstPacket as 1
     and previousPacket as 0, assume this indicates that the server saw the
     incoming packets from a different peer and thus as a different call.
     Fail the call with error -ENETRESET.

 (2) Also fail the call if a similar OUT_OF_SEQUENCE ACK occurs if the
     first packet has been hard-ACK'd.  If it hasn't been hard-ACK'd, the
     ACK packet will cause it to get retransmitted, so the call will just
     be repeated.

 (3) Make afs_select_fileserver() treat -ENETRESET as a straight fail of
     the operation.

 (4) Prioritise the error code over things like -ECONNRESET as the server
     did actually respond.

 (5) Make writeback treat -ENETRESET as a retryable error and make it
     redirty all the pages involved in a write so that the VM will retry.

Note that there is still a circumstance that I can't easily deal with: if
the operation is fully received and processed by the server, but the reply
is lost due to address change.  There's no way to know if the op happened.
We can examine the server, but a conflicting change could have been made by
a third party - and we can't tell the difference.  In such a case, a
message like:

    kAFS: vnode modified {100058:146266} b7->b8 YFS.StoreData64 (op=2646a)

will be logged to dmesg on the next op to touch the file and the client
will reset the inode state, including invalidating clean parts of the
pagecache.

Reported-by: Marc Dionne 
Signed-off-by: David Howells 
cc: linux-afs@lists.infradead.org
Link: http://lists.infradead.org/pipermail/linux-afs/2021-December/004811.html # v1
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin

rxrpc, afs: Fix selection of abort codes

2022-06-09T08:25:30+00:00

[ Upstream commit de696c4784f0706884458893c5a6c39b3a3ff65c ]

The RX_USER_ABORT code should really only be used to indicate that the user
of the rxrpc service (ie. userspace) implicitly caused a call to be aborted
- for instance if the AF_RXRPC socket is closed whilst the call was in
progress.  (The user may also explicitly abort a call and specify the abort
code to use).

Change some of the points of generation to use other abort codes instead:

 (1) Abort the call with RXGEN_SS_UNMARSHAL or RXGEN_CC_UNMARSHAL if we see
     ENOMEM and EFAULT during received data delivery and abort with
     RX_CALL_DEAD in the default case.

 (2) Abort with RXGEN_SS_MARSHAL if we get ENOMEM whilst trying to send a
     reply.

 (3) Abort with RX_CALL_DEAD if we stop hearing from the peer if we had
     heard from the peer and abort with RX_CALL_TIMEOUT if we hadn't.

 (4) Abort with RX_CALL_DEAD if we try to disconnect a call that's not
     completed successfully or been aborted.

Reported-by: Jeffrey Altman 
Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin

afs: Fix afs_getattr() to refetch file status if callback break occurred

2022-05-25T07:59:15+00:00

[ Upstream commit 2aeb8c86d49967552394d5e723f87454cb53f501 ]

If a callback break occurs (change notification), afs_getattr() needs to
issue an FS.FetchStatus RPC operation to update the status of the file
being examined by the stat-family of system calls.

Fix afs_getattr() to do this if AFS_VNODE_CB_PROMISED has been cleared
on a vnode by a callback break.  Skip this if AT_STATX_DONT_SYNC is set.

This can be tested by appending to a file on one AFS client and then
using "stat -L" to examine its length on a machine running kafs.  This
can also be watched through tracing on the kafs machine.  The callback
break is seen:

     kworker/1:1-46      [001] .....   978.910812: afs_cb_call: c=0000005f YFSCB.CallBack
     kworker/1:1-46      [001] ...1.   978.910829: afs_cb_break: 100058:23b4c:242d2c2 b=2 s=1 break-cb
     kworker/1:1-46      [001] .....   978.911062: afs_call_done:    c=0000005f ret=0 ab=0 [0000000082994ead]

And then the stat command generated no traffic if unpatched, but with
this change a call to fetch the status can be observed:

            stat-4471    [000] .....   986.744122: afs_make_fs_call: c=000000ab 100058:023b4c:242d2c2 YFS.FetchStatus
            stat-4471    [000] .....   986.745578: afs_call_done:    c=000000ab ret=0 ab=0 [0000000087fc8c84]

Fixes: 08e0e7c82eea ("[AF_RXRPC]: Make the in-kernel AFS filesystem use AF_RXRPC.")
Reported-by: Markus Suvanto 
Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org
Tested-by: Markus Suvanto 
Tested-by: kafs-testing+fedora34_64checkkafs-build-496@auristor.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216010
Link: https://lore.kernel.org/r/165308359800.162686.14122417881564420962.stgit@warthog.procyon.org.uk/ # v1
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

afs: Fix potential thrashing in afs writeback

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

In afs_writepages_region(), if the dirty page we find is undergoing
writeback or write to cache, but the sync_mode is WB_SYNC_NONE, we go
round the loop trying the same page again and again with no pausing or
waiting unless and until another thread manages to clear the writeback
and fscache flags.

Fix this with three measures:

 (1) Advance start to after the page we found.

 (2) Break out of the loop and return if rescheduling is requested.

 (3) Arbitrarily give up after a maximum of 5 skips.

Fixes: 31143d5d515e ("AFS: implement basic file write support")
Reported-by: Marc Dionne 
Signed-off-by: David Howells 
Tested-by: Marc Dionne 
Acked-by: Marc Dionne 
Link: https://lore.kernel.org/r/164692725757.2097000.2060513769492301854.stgit@warthog.procyon.org.uk/ # v1
Signed-off-by: Linus Torvalds

proc: remove PDE_DATA() completely

2022-01-22T06:33:37+00:00

Remove PDE_DATA() completely and replace it with pde_data().

[akpm@linux-foundation.org: fix naming clash in drivers/nubus/proc.c]
[akpm@linux-foundation.org: now fix it properly]

Link: https://lkml.kernel.org/r/20211124081956.87711-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song 
Acked-by: Christian Brauner 
Cc: Alexey Dobriyan 
Cc: Alexey Gladkov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'fscache-rewrite-20220111' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

2022-01-12T21:45:12+00:00

Pull fscache rewrite from David Howells:
"This is a set of patches that rewrites the fscache driver and the
cachefiles driver, significantly simplifying the code compared to
what's upstream, removing the complex operation scheduling and object
state machine in favour of something much smaller and simpler.

The series is structured such that the first few patches disable
fscache use by the network filesystems using it, remove the cachefiles
driver entirely and as much of the fscache driver as can be got away
with without causing build failures in the network filesystems.

The patches after that recreate fscache and then cachefiles,
attempting to add the pieces in a logical order. Finally, the
filesystems are reenabled and then the very last patch changes the
documentation.

[!] Note: I have dropped the cifs patch for the moment, leaving local
caching in cifs disabled. I've been having trouble getting that
working. I think I have it done, but it needs more testing (there
seem to be some test failures occurring with v5.16 also from
xfstests), so I propose deferring that patch to the end of the
merge window.

WHY REWRITE?
============

Fscache's operation scheduling API was intended to handle sequencing
of cache operations, which were all required (where possible) to run
asynchronously in parallel with the operations being done by the
network filesystem, whilst allowing the cache to be brought online and
offline and to interrupt service for invalidation.

With the advent of the tmpfile capacity in the VFS, however, an
opportunity arises to do invalidation much more simply, without having
to wait for I/O that's actually in progress: Cachefiles can simply
create a tmpfile, cut over the file pointer for the backing object
attached to a cookie and abandon the in-progress I/O, dismissing it
upon completion.

Future work here would involve using Omar Sandoval's vfs_link() with
AT_LINK_REPLACE[1] to allow an extant file to be displaced by a new
hard link from a tmpfile as currently I have to unlink the old file
first.

These patches can also simplify the object state handling as I/O
operations to the cache don't all have to be brought to a stop in
order to invalidate a file. To that end, and with an eye on to writing
a new backing cache model in the future, I've taken the opportunity to
simplify the indexing structure.

I've separated the index cookie concept from the file cookie concept
by C type now. The former is now called a "volume cookie" (struct
fscache_volume) and there is a container of file cookies. There are
then just the two levels. All the index cookie levels are collapsed
into a single volume cookie, and this has a single printable string as
a key. For instance, an AFS volume would have a key of something like
"afs,example.com,1000555", combining the filesystem name, cell name
and volume ID. This is freeform, but must not have '/' chars in it.

I've also eliminated all pointers back from fscache into the network
filesystem. This required the duplication of a little bit of data in
the cookie (cookie key, coherency data and file size), but it's not
actually that much. This gets rid of problems with making sure we keep
netfs data structures around so that the cache can access them.

These patches mean that most of the code that was in the drivers
before is simply gone and those drivers are now almost entirely new
code. That being the case, there doesn't seem any particular reason to
try and maintain bisectability across it. Further, there has to be a
point in the middle where things are cut over as there's a single
point everything has to go through (ie. /dev/cachefiles) and it can't
be in use by two drivers at once.

ISSUES YET OUTSTANDING
======================

There are some issues still outstanding, unaddressed by this patchset,
that will need fixing in future patchsets, but that don't stop this
series from being usable:

(1) The cachefiles driver needs to stop using the backing filesystem's
metadata to store information about what parts of the cache are
populated. This is not reliable with modern extent-based
filesystems.

Fixing this is deferred to a separate patchset as it involves
negotiation with the network filesystem and the VM as to how much
data to download to fulfil a read - which brings me on to (2)...

(2) NFS (and CIFS with the dropped patch) do not take account of how
the cache would like I/O to be structured to meet its granularity
requirements. Previously, the cache used page granularity, which
was fine as the network filesystems also dealt in page
granularity, and the backing filesystem (ext4, xfs or whatever)
did whatever it did out of sight. However, we now have folios to
deal with and the cache will now have to store its own metadata to
track its contents.

The change I'm looking at making for cachefiles is to store
content bitmaps in one or more xattrs and making a bit in the map
correspond to something like a 256KiB block. However, the size of
an xattr and the fact that they have to be read/updated in one go
means that I'm looking at covering 1GiB of data per 512-byte map
and storing each map in an xattr. Cachefiles has the potential to
grow into a fully fledged filesystem of its very own if I'm not
careful.

However, I'm also looking at changing things even more radically
and going to a different model of how the cache is arranged and
managed - one that's more akin to the way, say, openafs does
things - which brings me on to (3)...

(3) The way cachefilesd does culling is very inefficient for large
caches and it would be better to move it into the kernel if I can
as cachefilesd has to keep asking the kernel if it can cull a
file. Changing the way the backend works would allow this to be
addressed.

BITS THAT MAY BE CONTROVERSIAL
==============================

There are some bits I've added that may be controversial:

(1) I've provided a flag, S_KERNEL_FILE, that cachefiles uses to check
if a files is already being used by some other kernel service
(e.g. a duplicate cachefiles cache in the same directory) and
reject it if it is. This isn't entirely necessary, but it helps
prevent accidental data corruption.

I don't want to use S_SWAPFILE as that has other effects, but
quite possibly swapon() should set S_KERNEL_FILE too.

Note that it doesn't prevent userspace from interfering, though
perhaps it should. (I have made it prevent a marked directory from
being rmdir-able).

(2) Cachefiles wants to keep the backing file for a cookie open whilst
we might need to write to it from network filesystem writeback.
The problem is that the network filesystem unuses its cookie when
its file is closed, and so we have nothing pinning the cachefiles
file open and it will get closed automatically after a short time
to avoid EMFILE/ENFILE problems.

Reopening the cache file, however, is a problem if this is being
done due to writeback triggered by exit(). Some filesystems will
oops if we try to open a file in that context because they want to
access current->fs or suchlike.

To get around this, I added the following:

(A) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network
filesystem inode to indicate that we have a usage count on the
cookie caching that inode.

(B) A flag in struct writeback_control, unpinned_fscache_wb, that
is set when __writeback_single_inode() clears the last dirty
page from i_pages - at which point it clears
I_PINNING_FSCACHE_WB and sets this flag.

This has to be done here so that clearing I_PINNING_FSCACHE_WB
can be done atomically with the check of PAGECACHE_TAG_DIRTY
that clears I_DIRTY_PAGES.

(C) A function, fscache_set_page_dirty(), which if it is not set,
sets I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to
pin the cache resources.

(D) A function, fscache_unpin_writeback(), to be called by
->write_inode() to unuse the cookie.

(E) A function, fscache_clear_inode_writeback(), to be called when
the inode is evicted, before clear_inode() is called. This
cleans up any lingering I_PINNING_FSCACHE_WB.

The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the
cache as well as to the server.

For the future, I'm working on write helpers for netfs lib that
should allow this facility to be removed by keeping track of the
dirty regions separately - but that's incomplete at the moment and
is also going to be affected by folios, one way or another, since
it deals with pages"

Link: https://lore.kernel.org/all/510611.1641942444@warthog.procyon.org.uk/
Tested-by: Dominique Martinet # 9p
Tested-by: kafs-testing@auristor.com # afs
Tested-by: Jeff Layton # ceph
Tested-by: Dave Wysochanski # nfs
Tested-by: Daire Byrne # nfs

* tag 'fscache-rewrite-20220111' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs: (67 commits)
9p, afs, ceph, nfs: Use current_is_kswapd() rather than gfpflags_allow_blocking()
fscache: Add a tracepoint for cookie use/unuse
fscache: Rewrite documentation
ceph: add fscache writeback support
ceph: conversion to new fscache API
nfs: Implement cache I/O by accessing the cache directly
nfs: Convert to new fscache volume/cookie API
9p: Copy local writes to the cache when writing to the server
9p: Use fscache indexing rewrite and reenable caching
afs: Skip truncation on the server of data we haven't written yet
afs: Copy local writes to the cache when writing to the server
afs: Convert afs to use the new fscache API
fscache, cachefiles: Display stat of culling events
fscache, cachefiles: Display stats of no-space events
cachefiles: Allow cachefiles to actually function
fscache, cachefiles: Store the volume coherency data
cachefiles: Implement the I/O routines
cachefiles: Implement cookie resize for truncate
cachefiles: Implement begin and end I/O operation
cachefiles: Implement backing file wrangling
...

9p, afs, ceph, nfs: Use current_is_kswapd() rather than gfpflags_allow_blocking()

2022-01-11T22:27:42+00:00

In 9p, afs ceph, and nfs, gfpflags_allow_blocking() (which wraps a
test for __GFP_DIRECT_RECLAIM being set) is used to determine if
->releasepage() should wait for the completion of a DIO write to fscache
with something like:

	if (folio_test_fscache(folio)) {
		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
			return false;
		folio_wait_fscache(folio);
	}

Instead, current_is_kswapd() should be used instead.

Note that this is based on a patch originally by Zhaoyang Huang[1].  In
addition to extending it to the other network filesystems and putting it on
top of my fscache rewrite, it also needs to include linux/swap.h in a bunch
of places.  Can current_is_kswapd() be moved to linux/mm.h?

Changes
=======
ver #5:
 - Dropping the changes for cifs.

Originally-signed-off-by: Zhaoyang Huang 
Co-developed-by: David Howells 
Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: Zhaoyang Huang 
cc: Dominique Martinet 
cc: Marc Dionne 
cc: Steve French 
cc: Trond Myklebust 
cc: linux-cachefs@redhat.com
cc: v9fs-developer@lists.sourceforge.net
cc: linux-afs@lists.infradead.org
cc: ceph-devel@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/1638952658-20285-1-git-send-email-huangzhaoyang@gmail.com/ [1]
Link: https://lore.kernel.org/r/164021590773.640689.16777975200823659231.stgit@warthog.procyon.org.uk/ # v4

afs: Skip truncation on the server of data we haven't written yet

2022-01-07T13:44:56+00:00

Don't send a truncation RPC to the server if we're only shortening data
that's in the pagecache and is beyond the server's EOF.

Also don't automatically force writeback on setattr, but do wait to store
RPCs that are in the region to be removed on a shortening truncation.

Signed-off-by: David Howells 
Tested-by: kafs-testing@auristor.com
Acked-by: Jeff Layton 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/163819663275.215744.4781075713714590913.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906972600.143852.14237659724463048094.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967177522.1823006.15336589054269480601.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021571880.640689.1837025861707111004.stgit@warthog.procyon.org.uk/ # v4

afs: Copy local writes to the cache when writing to the server

2022-01-07T13:44:52+00:00

When writing to the server from afs_writepage() or afs_writepages(), copy
the data to the cache object too.

To make this possible, the cookie must have its active users count
incremented when the page is dirtied and kept incremented until we manage
to clean up all the pages.  This allows the writeback to take place after
the last file struct is released.

Signed-off-by: David Howells 
Tested-by: kafs-testing@auristor.com
Acked-by: Jeff Layton 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819662333.215744.7531373404219224438.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906970998.143852.674420788614608063.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967176564.1823006.16666056085593949570.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021570208.640689.9193494979708031862.stgit@warthog.procyon.org.uk/ # v4