Fix the coherency management of mmap'd data such that 3rd-party changes
become visible as soon as possible after the callback notification is
delivered by the fileserver. This is done by the following means:
(1) When we break a callback on a vnode specified by the CB.CallBack call
from the server, we queue a work item (vnode->cb_work) to go and
clobber all the PTEs mapping to that inode.
This causes the CPU to trip through the ->map_pages() and
->page_mkwrite() handlers if userspace attempts to access the page(s)
again.
(Ideally, this would be done in the service handler for CB.CallBack,
but the server is waiting for our reply before considering, and we
have a list of vnodes, all of which need breaking - and the process of
getting the mmap_lock and stripping the PTEs on all CPUs could be
quite slow.)
(2) Call afs_validate() from the ->map_pages() handler to check to see if
the file has changed and to get a new callback promise from the
server.
Also handle the fileserver telling us that it's dropping all callbacks,
possibly after it's been restarted by sending us a CB.InitCallBackState*
call by the following means:
(3) Maintain a per-cell list of afs files that are currently mmap'd
(cell->fs_open_mmaps).
(4) Add a work item to each server that is invoked if there are any open
mmaps when CB.InitCallBackState happens. This work item goes through
the aforementioned list and invokes the vnode->cb_work work item for
each one that is currently using this server.
This causes the PTEs to be cleared, causing ->map_pages() or
->page_mkwrite() to be called again, thereby calling afs_validate()
again.
I've chosen to simply strip the PTEs at the point of notification reception
rather than invalidate all the pages as well because (a) it's faster, (b)
we may get a notification for other reasons than the data being altered (in
which case we don't want to clobber the pagecache) and (c) we need to ask
the server to find out - and I don't want to wait for the reply before
holding up userspace.
This was tested using the attached test program:
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
int main(int argc, char *argv[])
{
size_t size = getpagesize();
unsigned char *p;
bool mod = (argc == 3);
int fd;
if (argc != 2 && argc != 3) {
fprintf(stderr, "Format: %s <file> [mod]\n", argv[0]);
exit(2);
}
fd = open(argv[1], mod ? O_RDWR : O_RDONLY);
if (fd < 0) {
perror(argv[1]);
exit(1);
}
p = mmap(NULL, size, mod ? PROT_READ|PROT_WRITE : PROT_READ,
MAP_SHARED, fd, 0);
if (p == MAP_FAILED) {
perror("mmap");
exit(1);
}
for (;;) {
if (mod) {
p[0]++;
msync(p, size, MS_ASYNC);
fsync(fd);
}
printf("%02x", p[0]);
fflush(stdout);
sleep(1);
}
}
It runs in two modes: in one mode, it mmaps a file, then sits in a loop
reading the first byte, printing it and sleeping for a second; in the
second mode it mmaps a file, then sits in a loop incrementing the first
byte and flushing, then printing and sleeping.
Two instances of this program can be run on different machines, one doing
the reading and one doing the writing. The reader should see the changes
made by the writer, but without this patch, they aren't because validity
checking is being done lazily - only on entry to the filesystem.
Testing the InitCallBackState change is more complicated. The server has
to be taken offline, the saved callback state file removed and then the
server restarted whilst the reading-mode program continues to run. The
client machine then has to poke the server to trigger the InitCallBackState
call.
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Markus Suvanto <markus.suvanto@gmail.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/163111668833.283156.382633263709075739.stgit@warthog.procyon.org.uk/
There's a memory leak in afs_parse_source() whereby multiple source=
parameters overwrite fc->source in the fs_context struct without freeing
the previously recorded source.
Fix this by only permitting a single source parameter and rejecting with
an error all subsequent ones.
This was caught by syzbot with the kernel memory leak detector, showing
something like the following trace:
unreferenced object 0xffff888114375440 (size 32):
comm "repro", pid 5168, jiffies 4294923723 (age 569.948s)
backtrace:
slab_post_alloc_hook+0x42/0x79
__kmalloc_track_caller+0x125/0x16a
kmemdup_nul+0x24/0x3c
vfs_parse_fs_string+0x5a/0xa1
generic_parse_monolithic+0x9d/0xc5
do_new_mount+0x10d/0x15a
do_mount+0x5f/0x8e
__do_sys_mount+0xff/0x127
do_syscall_64+0x2d/0x3a
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fixes: 13fcc68370 ("afs: Add fs_context support")
Reported-by: syzbot+86dc6632faaca40133ab@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge tag 'afs-fixes-20201016' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
Pull afs updates from David Howells:
"A collection of fixes to fix afs_cell struct refcounting, thereby
fixing a slew of related syzbot bugs:
- Fix the cell tree in the netns to use an rwsem rather than RCU.
There seem to be some problems deriving from the use of RCU and a
seqlock to walk the rbtree, but it's not entirely clear what since
there are several different failures being seen.
Changing things to use an rwsem instead makes it more robust. The
extra performance derived from using RCU isn't necessary in this
case since the only time we're looking up a cell is during mount or
when cells are being manually added.
- Fix the refcounting by splitting the usage counter into a memory
refcount and an active users counter. The usage counter was doing
double duty, keeping track of whether a cell is still in use and
keeping track of when it needs to be destroyed - but this makes the
clean up tricky. Separating these out simplifies the logic.
- Fix purging a cell that has an alias. A cell alias pins the cell
it's an alias of, but the alias is always later in the list. Trying
to purge in a single pass causes rmmod to hang in such a case.
- Fix cell removal. If a cell's manager is requeued whilst it's
removing itself, the manager will run again and re-remove itself,
causing problems in various places. Follow Hillf Danton's
suggestion to insert a more terminal state that causes the manager
to do nothing post-removal.
In additional to the above, two other changes:
- Add a tracepoint for the cell refcount and active users count. This
helped with debugging the above and may be useful again in future.
- Downgrade an assertion to a print when a still-active server is
seen during purging. This was happening as a consequence of
incomplete cell removal before the servers were cleaned up"
* tag 'afs-fixes-20201016' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
afs: Don't assert on unpurgeable server records
afs: Add tracing for cell refcount and active user count
afs: Fix cell removal
afs: Fix cell purging with aliases
afs: Fix cell refcounting by splitting the usage counter
afs: Fix rapid cell addition/removal by not using RCU on cells tree
Add a tracepoint to log the cell refcount and active user count and pass in
a reason code through various functions that manipulate these counters.
Additionally, a helper function, afs_see_cell(), is provided to log
interesting places that deal with a cell without actually doing any
accounting directly.
Signed-off-by: David Howells <dhowells@redhat.com>
Management of the lifetime of afs_cell struct has some problems due to the
usage counter being used to determine whether objects of that type are in
use in addition to whether anyone might be interested in the structure.
This is made trickier by cell objects being cached for a period of time in
case they're quickly reused as they hold the result of a setup process that
may be slow (DNS lookups, AFS RPC ops).
Problems include the cached root volume from alias resolution pinning its
parent cell record, rmmod occasionally hanging and occasionally producing
assertion failures.
Fix this by splitting the count of active users from the struct reference
count. Things then work as follows:
(1) The cell cache keeps +1 on the cell's activity count and this has to
be dropped before the cell can be removed. afs_manage_cell() tries to
exchange the 1 to a 0 with the cells_lock write-locked, and if
successful, the record is removed from the net->cells.
(2) One struct ref is 'owned' by the activity count. That is put when the
active count is reduced to 0 (final_destruction label).
(3) A ref can be held on a cell whilst it is queued for management on a
work queue without confusing the active count. afs_queue_cell() is
added to wrap this.
(4) The queue's ref is dropped at the end of the management. This is
split out into a separate function, afs_manage_cell_work().
(5) The root volume record is put after a cell is removed (at the
final_destruction label) rather then in the RCU destruction routine.
(6) Volumes hold struct refs, but aren't active users.
(7) Both counts are displayed in /proc/net/afs/cells.
There are some management function changes:
(*) afs_put_cell() now just decrements the refcount and triggers the RCU
destruction if it becomes 0. It no longer sets a timer to have the
manager do this.
(*) afs_use_cell() and afs_unuse_cell() are added to increase and decrease
the active count. afs_unuse_cell() sets the management timer.
(*) afs_queue_cell() is added to queue a cell with approprate refs.
There are also some other fixes:
(*) Don't let /proc/net/afs/cells access a cell's vllist if it's NULL.
(*) Make sure that candidate cells in lookups are properly destroyed
rather than being simply kfree'd. This ensures the bits it points to
are destroyed also.
(*) afs_dec_cells_outstanding() is now called in cell destruction rather
than at "final_destruction". This ensures that cell->net is still
valid to the end of the destructor.
(*) As a consequence of the previous two changes, move the increment of
net->cells_outstanding that was at the point of insertion into the
tree to the allocation routine to correctly balance things.
Fixes: 989782dcdc ("afs: Overhaul cell database management")
Signed-off-by: David Howells <dhowells@redhat.com>
There are a number of problems that are being seen by the rapidly mounting
and unmounting an afs dynamic root with an explicit cell and volume
specified (which should probably be rejected, but that's a separate issue):
What the tests are doing is to look up/create a cell record for the name
given and then tear it down again without actually using it to try to talk
to a server. This is repeated endlessly, very fast, and the new cell
collides with the old one if it's not quick enough to reuse it.
It appears (as suggested by Hillf Danton) that the search through the RB
tree under a read_seqbegin_or_lock() under RCU conditions isn't safe and
that it's not blocking the write_seqlock(), despite taking two passes at
it. He suggested that the code should take a ref on the cell it's
attempting to look at - but this shouldn't be necessary until we've
compared the cell names. It's possible that I'm missing a barrier
somewhere.
However, using an RCU search for this is overkill, really - we only need to
access the cell name in a few places, and they're places where we're may
end up sleeping anyway.
Fix this by switching to an R/W semaphore instead.
Additionally, draw the down_read() call inside the function (renamed to
afs_find_cell()) since all the callers were taking the RCU read lock (or
should've been[*]).
[*] afs_probe_cell_name() should have been, but that doesn't appear to be
involved in the bug reports.
The symptoms of this look like:
general protection fault, probably for non-canonical address 0xf27d208691691fdb: 0000 [#1] PREEMPT SMP KASAN
KASAN: maybe wild-memory-access in range [0x93e924348b48fed8-0x93e924348b48fedf]
...
RIP: 0010:strncasecmp lib/string.c:52 [inline]
RIP: 0010:strncasecmp+0x5f/0x240 lib/string.c:43
afs_lookup_cell_rcu+0x313/0x720 fs/afs/cell.c:88
afs_lookup_cell+0x2ee/0x1440 fs/afs/cell.c:249
afs_parse_source fs/afs/super.c:290 [inline]
...
Fixes: 989782dcdc ("afs: Overhaul cell database management")
Reported-by: syzbot+459a5dce0b4cb70fd076@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Hillf Danton <hdanton@sina.com>
cc: syzkaller-bugs@googlegroups.com
Set up a readahead size by default, as very few users have a good
reason to change it. This means code, ecryptfs, and orangefs now
set up the values while they were previously missing it, while ubifs,
mtd and vboxsf manually set it to 0 to avoid readahead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: David Sterba <dsterba@suse.com> [btrfs]
Acked-by: Richard Weinberger <richard@nod.at> [ubifs, mtd]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Fix afs_statfs() so that the value for f_bavail and f_bfree don't go
"negative" if the number of blocks in use by a volume exceeds the max quota
for that volume.
Signed-off-by: David Howells <dhowells@redhat.com>
Reorganise afs_volume objects such that they're in a tree keyed on volume
ID, rooted at on an afs_cell object rather than being in multiple trees,
each of which is rooted on an afs_server object.
afs_server structs become per-cell and acquire a pointer to the cell.
The process of breaking a callback then starts with finding the server by
its network address, following that to the cell and then looking up each
volume ID in the volume tree.
This is simpler than the afs_vol_interest/afs_cb_interest N:M mapping web
and allows those structs and the code for maintaining them to be simplified
or removed.
It does make a couple of things a bit more tricky, though:
(1) Operations now start with a volume, not a server, so there can be more
than one answer as to whether or not the server we'll end up using
supports the FS.InlineBulkStatus RPC.
(2) CB RPC operations that specify the server UUID. There's still a tree
of servers by UUID on the afs_net struct, but the UUIDs in it aren't
guaranteed unique.
Signed-off-by: David Howells <dhowells@redhat.com>
Put in the first phase of cell alias detection. This part handles alias
detection for cells that have root.cell volumes (which is expected to be
likely).
When a cell becomes newly active, it is probed for its root.cell volume,
and if it has one, this volume is compared against other root.cell volumes
to find out if the list of fileserver UUIDs have any in common - and if
that's the case, do the address lists of those fileservers have any
addresses in common. If they do, the new cell is adjudged to be an alias
of the old cell and the old cell is used instead.
Comparing is aided by the server list in struct afs_server_list being
sorted in UUID order and the addresses in the fileserver address lists
being sorted in address order.
The cell then retains the afs_volume object for the root.cell volume, even
if it's not mounted for future alias checking.
This necessary because:
(1) Whilst fileservers have UUIDs that are meant to be globally unique, in
practice they are not because cells get cloned without changing the
UUIDs - so afs_server records need to be per cell.
(2) Sometimes the DNS is used to make cell aliases - but if we don't know
they're the same, we may end up with multiple superblocks and multiple
afs_server records for the same thing, impairing our ability to
deliver callback notifications of third party changes
(3) The fileserver RPC API doesn't contain the cell name, so it can't tell
us which cell it's notifying and can't see that a change made to to
one cell should notify the same client that's also accessed as the
other cell.
Reported-by: Jeffrey Altman <jaltman@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Turn the afs_operation struct into the main way that most fileserver
operations are managed. Various things are added to the struct, including
the following:
(1) All the parameters and results of the relevant operations are moved
into it, removing corresponding fields from the afs_call struct.
afs_call gets a pointer to the op.
(2) The target volume is made the main focus of the operation, rather than
the target vnode(s), and a bunch of op->vnode->volume are made
op->volume instead.
(3) Two vnode records are defined (op->file[]) for the vnode(s) involved
in most operations. The vnode record (struct afs_vnode_param)
contains:
- The vnode pointer.
- The fid of the vnode to be included in the parameters or that was
returned in the reply (eg. FS.MakeDir).
- The status and callback information that may be returned in the
reply about the vnode.
- Callback break and data version tracking for detecting
simultaneous third-parth changes.
(4) Pointers to dentries to be updated with new inodes.
(5) An operations table pointer. The table includes pointers to functions
for issuing AFS and YFS-variant RPCs, handling the success and abort
of an operation and handling post-I/O-lock local editing of a
directory.
To make this work, the following function restructuring is made:
(A) The rotation loop that issues calls to fileservers that can be found
in each function that wants to issue an RPC (such as afs_mkdir()) is
extracted out into common code, in a new file called fs_operation.c.
(B) The rotation loops, such as the one in afs_mkdir(), are replaced with
a much smaller piece of code that allocates an operation, sets the
parameters and then calls out to the common code to do the actual
work.
(C) The code for handling the success and failure of an operation are
moved into operation functions (as (5) above) and these are called
from the core code at appropriate times.
(D) The pseudo inode getting stuff used by the dynamic root code is moved
over into dynroot.c.
(E) struct afs_iget_data is absorbed into the operation struct and
afs_iget() expects to be given an op pointer and a vnode record.
(F) Point (E) doesn't work for the root dir of a volume, but we know the
FID in advance (it's always vnode 1, unique 1), so a separate inode
getter, afs_root_iget(), is provided to special-case that.
(G) The inode status init/update functions now also take an op and a vnode
record.
(H) The RPC marshalling functions now, for the most part, just take an
afs_operation struct as their only argument. All the data they need
is held there. The result delivery functions write their answers
there as well.
(I) The call is attached to the operation and then the operation core does
the waiting.
And then the new operation code is, for the moment, made to just initialise
the operation, get the appropriate vnode I/O locks and do the same rotation
loop as before.
This lays the foundation for the following changes in the future:
(*) Overhauling the rotation (again).
(*) Support for asynchronous I/O, where the fileserver rotation must be
done asynchronously also.
Signed-off-by: David Howells <dhowells@redhat.com>
As a prelude to implementing asynchronous fileserver operations in the afs
filesystem, rename struct afs_fs_cursor to afs_operation.
This struct is going to form the core of the operation management and is
going to acquire more members in later.
Signed-off-by: David Howells <dhowells@redhat.com>
Unused now.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Don't do a single array; attach them to fsparam_enum() entry
instead. And don't bother trying to embed the names into those -
it actually loses memory, with no real speedup worth mentioning.
Simplifies validation as well.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Fix missing cell comparison in afs_test_super(). Without this, any pair
volumes that have the same volume ID will share a superblock, no matter the
cell, unless they're in different network namespaces.
Normally, most users will only deal with a single cell and so they won't
see this. Even if they do look into a second cell, they won't see a
problem unless they happen to hit a volume with the same ID as one they've
already got mounted.
Before the patch:
# ls /afs/grand.central.org/archive
linuxdev/ mailman/ moin/ mysql/ pipermail/ stage/ twiki/
# ls /afs/kth.se/
linuxdev/ mailman/ moin/ mysql/ pipermail/ stage/ twiki/
# cat /proc/mounts | grep afs
none /afs afs rw,relatime,dyn,autocell 0 0
#grand.central.org:root.cell /afs/grand.central.org afs ro,relatime 0 0
#grand.central.org:root.archive /afs/grand.central.org/archive afs ro,relatime 0 0
#grand.central.org:root.archive /afs/kth.se afs ro,relatime 0 0
After the patch:
# ls /afs/grand.central.org/archive
linuxdev/ mailman/ moin/ mysql/ pipermail/ stage/ twiki/
# ls /afs/kth.se/
admin/ common/ install/ OldFiles/ service/ system/
bakrestores/ home/ misc/ pkg/ src/ wsadmin/
# cat /proc/mounts | grep afs
none /afs afs rw,relatime,dyn,autocell 0 0
#grand.central.org:root.cell /afs/grand.central.org afs ro,relatime 0 0
#grand.central.org:root.archive /afs/grand.central.org/archive afs ro,relatime 0 0
#kth.se:root.cell /afs/kth.se afs ro,relatime 0 0
Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Carsten Jacobi <jacobi@de.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Tested-by: Jonathan Billings <jsbillings@jsbillings.org>
cc: Todd DeSantis <atd@us.ibm.com>
Make the AFS dynamic root superblock R/W so that SELinux can set the
security label on it. Without this, upgrades to, say, the Fedora
filesystem-afs RPM fail if afs is mounted on it because the SELinux label
can't be (re-)applied.
It might be better to make it possible to bypass the R/O check for LSM
label application through setxattr.
Fixes: 4d673da145 ("afs: Support the AFS dynamic root")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: selinux@vger.kernel.org
cc: linux-security-module@vger.kernel.org
By default s_maxbytes is set to MAX_NON_LFS, which limits the usable
file size to 2GB, enforced by the vfs.
Commit b9b1f8d593 ("AFS: write support fixes") added support for the
64-bit fetch and store server operations, but did not change this value.
As a result, attempts to write past the 2G mark result in EFBIG errors:
$ dd if=/dev/zero of=foo bs=1M count=1 seek=2048
dd: error writing 'foo': File too large
Set s_maxbytes to MAX_LFS_FILESIZE.
Fixes: b9b1f8d593 ("AFS: write support fixes")
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pass the server and volume break counts from before the status fetch
operation that queried the attributes of a file into afs_iget5_set() so
that the new vnode's break counters can be initialised appropriately.
This allows detection of a volume or server break that happened whilst we
were fetching the status or setting up the vnode.
Fixes: c435ee3455 ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>
Use RCU-based freeing for afs_cb_interest struct objects and use RCU on
vnode->cb_interest. Use that change to allow afs_check_validity() to use
read_seqbegin_or_lock() instead of read_seqlock_excl().
This also requires the caller of afs_check_validity() to hold the RCU read
lock across the call.
Signed-off-by: David Howells <dhowells@redhat.com>
Don't save callback version and type fields as the version is about the
format of the callback information and the type is relative to the
particular RPC call.
Signed-off-by: David Howells <dhowells@redhat.com>
When applying the status and callback in the response of an operation,
apply them in the same critical section so that there's no race between
checking the callback state and checking status-dependent state (such as
the data version).
Fix this by:
(1) Allocating a joint {status,callback} record (afs_status_cb) before
calling the RPC function for each vnode for which the RPC reply
contains a status or a status plus a callback. A flag is set in the
record to indicate if a callback was actually received.
(2) These records are passed into the RPC functions to be filled in. The
afs_decode_status() and yfs_decode_status() functions are removed and
the cb_lock is no longer taken.
(3) xdr_decode_AFSFetchStatus() and xdr_decode_YFSFetchStatus() no longer
update the vnode.
(4) xdr_decode_AFSCallBack() and xdr_decode_YFSCallBack() no longer update
the vnode.
(5) vnodes, expected data-version numbers and callback break counters
(cb_break) no longer need to be passed to the reply delivery
functions.
Note that, for the moment, the file locking functions still need
access to both the call and the vnode at the same time.
(6) afs_vnode_commit_status() is now given the cb_break value and the
expected data_version and the task of applying the status and the
callback to the vnode are now done here.
This is done under a single taking of vnode->cb_lock.
(7) afs_pages_written_back() is now called by afs_store_data() rather than
by the reply delivery function.
afs_pages_written_back() has been moved to before the call point and
is now given the first and last page numbers rather than a pointer to
the call.
(8) The indicator from YFS.RemoveFile2 as to whether the target file
actually got removed (status.abort_code == VNOVNODE) rather than
merely dropping a link is now checked in afs_unlink rather than in
xdr_decode_YFSFetchStatus().
Supplementary fixes:
(*) afs_cache_permit() now gets the caller_access mask from the
afs_status_cb object rather than picking it out of the vnode's status
record. afs_fetch_status() returns caller_access through its argument
list for this purpose also.
(*) afs_inode_init_from_status() now uses a write lock on cb_lock rather
than a read lock and now sets the callback inside the same critical
section.
Fixes: c435ee3455 ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>
Make certain RPC operations non-interruptible, including:
(*) Set attributes
(*) Store data
We don't want to get interrupted during a flush on close, flush on
unlock, writeback or an inode update, leaving us in a state where we
still need to do the writeback or update.
(*) Extend lock
(*) Release lock
We don't want to get lock extension interrupted as the file locks on
the server are time-limited. Interruption during lock release is less
of an issue since the lock is time-limited, but it's better to
complete the release to avoid a several-minute wait to recover it.
*Setting* the lock isn't a problem if it's interrupted since we can
just return to the user and tell them they were interrupted - at
which point they can elect to retry.
(*) Silly unlink
We want to remove silly unlink files if we can, rather than leaving
them for the salvager to clear up.
Note that whilst these calls are no longer interruptible, they do have
timeouts on them, so if the server stops responding the call will fail with
something like ETIME or ECONNRESET.
Without this, the following:
kAFS: Unexpected error from FS.StoreData -512
appears in dmesg when a pending store data gets interrupted and some
processes may just hang.
Additionally, make the code that checks/updates the server record ignore
failure due to interruption if the main call is uninterruptible and if the
server has an address list. The next op will check it again since the
expiration time on the old list has past.
Fixes: d2ddc776a4 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Jonathan Billings <jsbillings@jsbillings.org>
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
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Merge tag 'afs-next-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
Pull AFS updates from David Howells:
"A set of fix and development patches for AFS for 5.2.
Summary:
- Fix the AFS file locking so that sqlite can run on an AFS mount and
also so that firefox and gnome can use a homedir that's mounted
through AFS.
This required emulation of fine-grained locking when the server
will only support whole-file locks and no upgrade/downgrade. Four
modes are provided, settable by mount parameter:
"flock=local" - No reference to the server
"flock=openafs" - Fine-grained locks are local-only, whole-file
locks require sufficient server locks
"flock=strict" - All locks require sufficient server locks
"flock=write" - Always get an exclusive server lock
If the volume is a read-only or backup volume, then flock=local for
that volume.
- Log extra information for a couple of cases where the client mucks
up somehow: AFS vnode with undefined type and dir check failure -
in both cases we seem to end up with unfilled data, but the issues
happen infrequently and are difficult to reproduce at will.
- Implement silly rename for unlink() and rename().
- Set i_blocks so that du can get some information about usage.
- Fix xattr handlers to return the right amount of data and to not
overflow buffers.
- Implement getting/setting raw AFS and YFS ACLs as xattrs"
* tag 'afs-next-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
afs: Implement YFS ACL setting
afs: Get YFS ACLs and information through xattrs
afs: implement acl setting
afs: Get an AFS3 ACL as an xattr
afs: Fix getting the afs.fid xattr
afs: Fix the afs.cell and afs.volume xattr handlers
afs: Calculate i_blocks based on file size
afs: Log more information for "kAFS: AFS vnode with undefined type\n"
afs: Provide mount-time configurable byte-range file locking emulation
afs: Add more tracepoints
afs: Implement sillyrename for unlink and rename
afs: Add directory reload tracepoint
afs: Handle lock rpc ops failing on a file that got deleted
afs: Improve dir check failure reports
afs: Add file locking tracepoints
afs: Further fix file locking
afs: Fix AFS file locking to allow fine grained locks
afs: Calculate lock extend timer from set/extend reply reception
afs: Split wait from afs_make_call()
Log more information when "kAFS: AFS vnode with undefined type\n" is
displayed due to a vnode record being retrieved from the server that
appears to have a duff file type (usually 0). This prints more information
to try and help pin down the problem.
Signed-off-by: David Howells <dhowells@redhat.com>
debugging printks left in ->destroy_inode() and so's the
update of inode count; we could take the latter to RCU-delayed
part (would take only moving the check on module exit past
rcu_barrier() there), but debugging output ought to either
stay where it is or go into ->evict_inode()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Provide byte-range file locking emulation that can be configured at mount
time to one of four modes:
(1) flock=local. Locking is done locally only and no reference is made to
the server.
(2) flock=openafs. Byte-range locking is done locally only; whole-file
locking is done with reference to the server. Whole-file locks cannot
be upgraded unless the client holds an exclusive lock.
(3) flock=strict. Byte-range and whole-file locking both require a
sufficient whole-file lock on the server.
(4) flock=write. As strict, but the client always gets an exclusive
whole-file lock on the server.
Signed-off-by: David Howells <dhowells@redhat.com>
Add four more tracepoints:
(1) afs_make_fs_call1 - Split from afs_make_fs_call but takes a filename
to log also.
(2) afs_make_fs_call2 - Like the above but takes two filenames to log.
(3) afs_lookup - Log the result of doing a successful lookup, including a
negative result (fid 0:0).
(4) afs_get_tree - Log the set up of a volume for mounting.
It also extends the name buffer on the afs_edit_dir tracepoint to 24 chars
and puts quotes around the filename in the text representation.
Signed-off-by: David Howells <dhowells@redhat.com>
Implement sillyrename for AFS unlink and rename, using the NFS variant
implementation as a basis.
Note that the asynchronous file locking extender/releaser has to be
notified with a state change to stop it complaining if there's a race
between that and the actual file deletion.
A tracepoint, afs_silly_rename, is also added to note the silly rename and
the cleanup. The afs_edit_dir tracepoint is given some extra reason
indicators and the afs_flock_ev tracepoint is given a silly-delete file
lock cancellation indicator.
Signed-off-by: David Howells <dhowells@redhat.com>
Pull vfs mount infrastructure updates from Al Viro:
"The rest of core infrastructure; no new syscalls in that pile, but the
old parts are switched to new infrastructure. At that point
conversions of individual filesystems can happen independently; some
are done here (afs, cgroup, procfs, etc.), there's also a large series
outside of that pile dealing with NFS (quite a bit of option-parsing
stuff is getting used there - it's one of the most convoluted
filesystems in terms of mount-related logics), but NFS bits are the
next cycle fodder.
It got seriously simplified since the last cycle; documentation is
probably the weakest bit at the moment - I considered dropping the
commit introducing Documentation/filesystems/mount_api.txt (cutting
the size increase by quarter ;-), but decided that it would be better
to fix it up after -rc1 instead.
That pile allows to do followup work in independent branches, which
should make life much easier for the next cycle. fs/super.c size
increase is unpleasant; there's a followup series that allows to
shrink it considerably, but I decided to leave that until the next
cycle"
* 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (41 commits)
afs: Use fs_context to pass parameters over automount
afs: Add fs_context support
vfs: Add some logging to the core users of the fs_context log
vfs: Implement logging through fs_context
vfs: Provide documentation for new mount API
vfs: Remove kern_mount_data()
hugetlbfs: Convert to fs_context
cpuset: Use fs_context
kernfs, sysfs, cgroup, intel_rdt: Support fs_context
cgroup: store a reference to cgroup_ns into cgroup_fs_context
cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper
cgroup_do_mount(): massage calling conventions
cgroup: stash cgroup_root reference into cgroup_fs_context
cgroup2: switch to option-by-option parsing
cgroup1: switch to option-by-option parsing
cgroup: take options parsing into ->parse_monolithic()
cgroup: fold cgroup1_mount() into cgroup1_get_tree()
cgroup: start switching to fs_context
ipc: Convert mqueue fs to fs_context
proc: Add fs_context support to procfs
...
All users of VM_MAX_READAHEAD actually convert it to kbytes and then to
pages. Define the macro explicitly as (SZ_128K / PAGE_SIZE). This
simplifies the expression in every filesystem. Also rename the macro to
VM_READAHEAD_PAGES to properly convey its meaning. Finally remove unused
VM_MIN_READAHEAD
[akpm@linux-foundation.org: fix fs/io_uring.c, per Stephen]
Link: http://lkml.kernel.org/r/20181221144053.24318-1-nborisov@suse.com
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Alter the AFS automounting code to create and modify an fs_context struct
when parameterising a new mount triggered by an AFS mountpoint rather than
constructing device name and option strings.
Also remove the cell=, vol= and rwpath options as they are then redundant.
The reason they existed is because the 'device name' may be derived
literally from a mountpoint object in the filesystem, so default cell and
parent-type information needed to be passed in by some other method from
the automount routines. The vol= option didn't end up being used.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Eric W. Biederman <ebiederm@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add fs_context support to the AFS filesystem, converting the parameter
parsing to store options there.
This will form the basis for namespace propagation over mountpoints within
the AFS model, thereby allowing AFS to be used in containers more easily.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Increase the sizes of the volume ID to 64 bits and the vnode ID (inode
number equivalent) to 96 bits to allow the support of YFS.
This requires the iget comparator to check the vnode->fid rather than i_ino
and i_generation as i_ino is not sufficiently capacious. It also requires
this data to be placed into the vnode cache key for fscache.
For the moment, just discard the top 32 bits of the vnode ID when returning
it though stat.
Signed-off-by: David Howells <dhowells@redhat.com>
Alter the dynroot mount so that cells created by manipulation of
/proc/fs/afs/cells and /proc/fs/afs/rootcell and by specification of a root
cell as a module parameter will cause directories for those cells to be
created in the dynamic root superblock for the network namespace[*].
To this end:
(1) Only one dynamic root superblock is now created per network namespace
and this is shared between all attempts to mount it. This makes it
easier to find the superblock to modify.
(2) When a dynamic root superblock is created, the list of cells is walked
and directories created for each cell already defined.
(3) When a new cell is added, if a dynamic root superblock exists, a
directory is created for it.
(4) When a cell is destroyed, the directory is removed.
(5) These directories are created by calling lookup_one_len() on the root
dir which automatically creates them if they don't exist.
[*] Inasmuch as network namespaces are currently supported here.
Signed-off-by: David Howells <dhowells@redhat.com>
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Merge tag 'afs-fixes-20180514' into afs-proc
backmerge AFS fixes that went into mainline and deal with
the conflict in fs/afs/fsclient.c
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Implement network namespacing within AFS, but don't yet let mounts occur
outside the init namespace. An additional patch will be required propagate
the network namespace across automounts.
Signed-off-by: David Howells <dhowells@redhat.com>
It's possible for an AFS file server to issue a whole-volume notification
that callbacks on all the vnodes in the file have been broken. This is
done for R/O and backup volumes (which don't have per-file callbacks) and
for things like a volume being taken offline.
Fix callback handling to detect whole-volume notifications, to track it
across operations and to check it during inode validation.
Fixes: c435ee3455 ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>
The afs directory loading code (primarily afs_read_dir()) locks all the
pages that hold a directory's content blob to defend against
getdents/getdents races and getdents/lookup races where the competitors
issue conflicting reads on the same data. As the reads will complete
consecutively, they may retrieve different versions of the data and
one may overwrite the data that the other is busy parsing.
Fix this by not locking the pages at all, but rather by turning the
validation lock into an rwsem and getting an exclusive lock on it whilst
reading the data or validating the attributes and a shared lock whilst
parsing the data. Sharing the attribute validation lock should be fine as
the data fetch will retrieve the attributes also.
The individual page locks aren't needed at all as the only place they're
being used is to serialise data loading.
Without this patch, the:
if (!test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) {
...
}
part of afs_read_dir() may be skipped, leaving the pages unlocked when we
hit the success: clause - in which case we try to unlock the not-locked
pages, leading to the following oops:
page:ffffe38b405b4300 count:3 mapcount:0 mapping:ffff98156c83a978 index:0x0
flags: 0xfffe000001004(referenced|private)
raw: 000fffe000001004 ffff98156c83a978 0000000000000000 00000003ffffffff
raw: dead000000000100 dead000000000200 0000000000000001 ffff98156b27c000
page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
page->mem_cgroup:ffff98156b27c000
------------[ cut here ]------------
kernel BUG at mm/filemap.c:1205!
...
RIP: 0010:unlock_page+0x43/0x50
...
Call Trace:
afs_dir_iterate+0x789/0x8f0 [kafs]
? _cond_resched+0x15/0x30
? kmem_cache_alloc_trace+0x166/0x1d0
? afs_do_lookup+0x69/0x490 [kafs]
? afs_do_lookup+0x101/0x490 [kafs]
? key_default_cmp+0x20/0x20
? request_key+0x3c/0x80
? afs_lookup+0xf1/0x340 [kafs]
? __lookup_slow+0x97/0x150
? lookup_slow+0x35/0x50
? walk_component+0x1bf/0x490
? path_lookupat.isra.52+0x75/0x200
? filename_lookup.part.66+0xa0/0x170
? afs_end_vnode_operation+0x41/0x60 [kafs]
? __check_object_size+0x9c/0x171
? strncpy_from_user+0x4a/0x170
? vfs_statx+0x73/0xe0
? __do_sys_newlstat+0x39/0x70
? __x64_sys_getdents+0xc9/0x140
? __x64_sys_getdents+0x140/0x140
? do_syscall_64+0x5b/0x160
? entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fixes: f3ddee8dc4 ("afs: Fix directory handling")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Split the AFS dynamic root stuff out of the main directory handling file
and into its own file as they share little in common.
The dynamic root code also gets its own dentry and inode ops tables.
Signed-off-by: David Howells <dhowells@redhat.com>
Support the AFS dynamic root which is a pseudo-volume that doesn't connect
to any server resource, but rather is just a root directory that
dynamically creates mountpoint directories where the name of such a
directory is the name of the cell.
Such a mount can be created thus:
mount -t afs none /afs -o dyn
Dynamic root superblocks aren't shared except by bind mounts and
propagation. Cell root volumes can then be mounted by referring to them by
name, e.g.:
ls /afs/grand.central.org/
ls /afs/.grand.central.org/
The kernel will upcall to consult the DNS if the address wasn't supplied
directly.
Signed-off-by: David Howells <dhowells@redhat.com>
When an AFS inode is allocated by afs_alloc_inode(), the allocated
afs_vnode struct isn't necessarily reset from the last time it was used as
an inode because the slab constructor is only invoked once when the memory
is obtained from the page allocator.
This means that information can leak from one inode to the next because
we're not calling kmem_cache_zalloc(). Some of the information isn't
reset, in particular the permit cache pointer.
Bring the clearances up to date.
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
This is a pure automated search-and-replace of the internal kernel
superblock flags.
The s_flags are now called SB_*, with the names and the values for the
moment mirroring the MS_* flags that they're equivalent to.
Note how the MS_xyz flags are the ones passed to the mount system call,
while the SB_xyz flags are what we then use in sb->s_flags.
The script to do this was:
# places to look in; re security/*: it generally should *not* be
# touched (that stuff parses mount(2) arguments directly), but
# there are two places where we really deal with superblock flags.
FILES="drivers/mtd drivers/staging/lustre fs ipc mm \
include/linux/fs.h include/uapi/linux/bfs_fs.h \
security/apparmor/apparmorfs.c security/apparmor/include/lib.h"
# the list of MS_... constants
SYMS="RDONLY NOSUID NODEV NOEXEC SYNCHRONOUS REMOUNT MANDLOCK \
DIRSYNC NOATIME NODIRATIME BIND MOVE REC VERBOSE SILENT \
POSIXACL UNBINDABLE PRIVATE SLAVE SHARED RELATIME KERNMOUNT \
I_VERSION STRICTATIME LAZYTIME SUBMOUNT NOREMOTELOCK NOSEC BORN \
ACTIVE NOUSER"
SED_PROG=
for i in $SYMS; do SED_PROG="$SED_PROG -e s/MS_$i/SB_$i/g"; done
# we want files that contain at least one of MS_...,
# with fs/namespace.c and fs/pnode.c excluded.
L=$(for i in $SYMS; do git grep -w -l MS_$i $FILES; done| sort|uniq|grep -v '^fs/namespace.c'|grep -v '^fs/pnode.c')
for f in $L; do sed -i $f $SED_PROG; done
Requested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Get rid of the afs_writeback record that kAFS is using to match keys with
writes made by that key.
Instead, keep a list of keys that have a file open for writing and/or
sync'ing and iterate through those.
Signed-off-by: David Howells <dhowells@redhat.com>
The current code assumes that volumes and servers are per-cell and are
never shared, but this is not enforced, and, indeed, public cells do exist
that are aliases of each other. Further, an organisation can, say, set up
a public cell and a private cell with overlapping, but not identical, sets
of servers. The difference is purely in the database attached to the VL
servers.
The current code will malfunction if it sees a server in two cells as it
assumes global address -> server record mappings and that each server is in
just one cell.
Further, each server may have multiple addresses - and may have addresses
of different families (IPv4 and IPv6, say).
To this end, the following structural changes are made:
(1) Server record management is overhauled:
(a) Server records are made independent of cell. The namespace keeps
track of them, volume records have lists of them and each vnode
has a server on which its callback interest currently resides.
(b) The cell record no longer keeps a list of servers known to be in
that cell.
(c) The server records are now kept in a flat list because there's no
single address to sort on.
(d) Server records are now keyed by their UUID within the namespace.
(e) The addresses for a server are obtained with the VL.GetAddrsU
rather than with VL.GetEntryByName, using the server's UUID as a
parameter.
(f) Cached server records are garbage collected after a period of
non-use and are counted out of existence before purging is allowed
to complete. This protects the work functions against rmmod.
(g) The servers list is now in /proc/fs/afs/servers.
(2) Volume record management is overhauled:
(a) An RCU-replaceable server list is introduced. This tracks both
servers and their coresponding callback interests.
(b) The superblock is now keyed on cell record and numeric volume ID.
(c) The volume record is now tied to the superblock which mounts it,
and is activated when mounted and deactivated when unmounted.
This makes it easier to handle the cache cookie without causing a
double-use in fscache.
(d) The volume record is loaded from the VLDB using VL.GetEntryByNameU
to get the server UUID list.
(e) The volume name is updated if it is seen to have changed when the
volume is updated (the update is keyed on the volume ID).
(3) The vlocation record is got rid of and VLDB records are no longer
cached. Sufficient information is stored in the volume record, though
an update to a volume record is now no longer shared between related
volumes (volumes come in bundles of three: R/W, R/O and backup).
and the following procedural changes are made:
(1) The fileserver cursor introduced previously is now fleshed out and
used to iterate over fileservers and their addresses.
(2) Volume status is checked during iteration, and the server list is
replaced if a change is detected.
(3) Server status is checked during iteration, and the address list is
replaced if a change is detected.
(4) The abort code is saved into the address list cursor and -ECONNABORTED
returned in afs_make_call() if a remote abort happened rather than
translating the abort into an error message. This allows actions to
be taken depending on the abort code more easily.
(a) If a VMOVED abort is seen then this is handled by rechecking the
volume and restarting the iteration.
(b) If a VBUSY, VRESTARTING or VSALVAGING abort is seen then this is
handled by sleeping for a short period and retrying and/or trying
other servers that might serve that volume. A message is also
displayed once until the condition has cleared.
(c) If a VOFFLINE abort is seen, then this is handled as VBUSY for the
moment.
(d) If a VNOVOL abort is seen, the volume is rechecked in the VLDB to
see if it has been deleted; if not, the fileserver is probably
indicating that the volume couldn't be attached and needs
salvaging.
(e) If statfs() sees one of these aborts, it does not sleep, but
rather returns an error, so as not to block the umount program.
(5) The fileserver iteration functions in vnode.c are now merged into
their callers and more heavily macroised around the cursor. vnode.c
is removed.
(6) Operations on a particular vnode are serialised on that vnode because
the server will lock that vnode whilst it operates on it, so a second
op sent will just have to wait.
(7) Fileservers are probed with FS.GetCapabilities before being used.
This is where service upgrade will be done.
(8) A callback interest on a fileserver is set up before an FS operation
is performed and passed through to afs_make_call() so that it can be
set on the vnode if the operation returns a callback. The callback
interest is passed through to afs_iget() also so that it can be set
there too.
In general, record updating is done on an as-needed basis when we try to
access servers, volumes or vnodes rather than offloading it to work items
and special threads.
Notes:
(1) Pre AFS-3.4 servers are no longer supported, though this can be added
back if necessary (AFS-3.4 was released in 1998).
(2) VBUSY is retried forever for the moment at intervals of 1s.
(3) /proc/fs/afs/<cell>/servers no longer exists.
Signed-off-by: David Howells <dhowells@redhat.com>
Overhaul the way that the in-kernel AFS client keeps track of cells in the
following manner:
(1) Cells are now held in an rbtree to make walking them quicker and RCU
managed (though this is probably overkill).
(2) Cells now have a manager work item that:
(A) Looks after fetching and refreshing the VL server list.
(B) Manages cell record lifetime, including initialising and
destruction.
(B) Manages cell record caching whereby threads are kept around for a
certain time after last use and then destroyed.
(C) Manages the FS-Cache index cookie for a cell. It is not permitted
for a cookie to be in use twice, so we have to be careful to not
allow a new cell record to exist at the same time as an old record
of the same name.
(3) Each AFS network namespace is given a manager work item that manages
the cells within it, maintaining a single timer to prod cells into
updating their DNS records.
This uses the reduce_timer() facility to make the timer expire at the
soonest timed event that needs happening.
(4) When a module is being unloaded, cells and cell managers are now
counted out using dec_after_work() to make sure the module text is
pinned until after the data structures have been cleaned up.
(5) Each cell's VL server list is now protected by a seqlock rather than a
semaphore.
Signed-off-by: David Howells <dhowells@redhat.com>
Overhaul permit caching in AFS by making it per-vnode and sharing permit
lists where possible.
When most of the fileserver operations are called, they return a status
structure indicating the (revised) details of the vnode or vnodes involved
in the operation. This includes the access mark derived from the ACL
(named CallerAccess in the protocol definition file). This is cacheable
and if the ACL changes, the server will tell us that it is breaking the
callback promise, at which point we can discard the currently cached
permits.
With this patch, the afs_permits structure has, at the end, an array of
{ key, CallerAccess } elements, sorted by key pointer. This is then cached
in a hash table so that it can be shared between vnodes with the same
access permits.
Permit lists can only be shared if they contain the exact same set of
key->CallerAccess mappings.
Note that that table is global rather than being per-net_ns. If the keys
in a permit list cross net_ns boundaries, there is no problem sharing the
cached permits, since the permits are just integer masks.
Since permit lists pin keys, the permit cache also makes it easier for a
future patch to find all occurrences of a key and remove them by means of
setting the afs_permits::invalidated flag and then clearing the appropriate
key pointer. In such an event, memory barriers will need adding.
Lastly, the permit caching is skipped if the server has sent either a
vnode-specific or an entire-server callback since the start of the
operation.
Signed-off-by: David Howells <dhowells@redhat.com>
Overhaul the AFS callback handling by the following means:
(1) Don't give up callback promises on vnodes that we are no longer using,
rather let them just expire on the server or let the server break
them. This is actually more efficient for the server as the callback
lookup is expensive if there are lots of extant callbacks.
(2) Only give up the callback promises we have from a server when the
server record is destroyed. Then we can just give up *all* the
callback promises on it in one go.
(3) Servers can end up being shared between cells if cells are aliased, so
don't add all the vnodes being backed by a particular server into a
big FID-indexed tree on that server as there may be duplicates.
Instead have each volume instance (~= superblock) register an interest
in a server as it starts to make use of it and use this to allow the
processor for callbacks from the server to find the superblock and
thence the inode corresponding to the FID being broken by means of
ilookup_nowait().
(4) Rather than iterating over the entire callback list when a mass-break
comes in from the server, maintain a counter of mass-breaks in
afs_server (cb_seq) and make afs_validate() check it against the copy
in afs_vnode.
It would be nice not to have to take a read_lock whilst doing this,
but that's tricky without using RCU.
(5) Save a ref on the fileserver we're using for a call in the afs_call
struct so that we can access its cb_s_break during call decoding.
(6) Write-lock around callback and status storage in a vnode and read-lock
around getattr so that we don't see the status mid-update.
This has the following consequences:
(1) Data invalidation isn't seen until someone calls afs_validate() on a
vnode. Unfortunately, we need to use a key to query the server, but
getting one from a background thread is tricky without caching loads
of keys all over the place.
(2) Mass invalidation isn't seen until someone calls afs_validate().
(3) Callback breaking is going to hit the inode_hash_lock quite a bit.
Could this be replaced with rcu_read_lock() since inodes are destroyed
under RCU conditions.
Signed-off-by: David Howells <dhowells@redhat.com>
David Howells