forked from Minki/linux
mainlining shenanigans
0d74471924
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Merge tag 'afs-fixes-b-20190516' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
Pull AFS callback promise fixes from David Howells:
"This series fixes a bunch of problems in callback promise handling,
where a callback promise indicates a promise on the part of the server
to notify the client in the event of some sort of change to a file or
volume. In the event of a break, the client has to go and refetch the
client status from the server and discard any cached permission
information as the ACL might have changed.
The problem in the current code is that changes made by other clients
aren't always noticed, primarily because the file status information
and the callback information aren't updated in the same critical
section, even if these are carried in the same reply from an RPC
operation, and so the AFS_VNODE_CB_PROMISED flag is unreliable.
Arranging for them to be done in the same critical section during
reply decoding is tricky because of the FS.InlineBulkStatus op - which
has all the statuses in the reply arriving and then all the callbacks,
so they have to be buffered. It simplifies things a lot to move the
critical section out of the decode phase and do it after the RPC
function returns.
Also new inodes (either newly fetched or newly created) aren't
properly managed against a callback break happening before we get the
local inode up and running.
Fix this by:
- There's now a combined file status and callback record (struct
afs_status_cb) to carry both plus some flags.
- Each operation wrapper function allocates sufficient afs_status_cb
records for all the vnodes it is interested in and passes them into
RPC operations to be filled in from the reply.
- The FileStatus and CallBack record decoders no longer apply the
new/revised status and callback information to the inode/vnode at
the point of decoding and instead store the information into the
record from (2).
- afs_vnode_commit_status() then revises the file status, detects
deletion and notes callback information inside of a single critical
section. It also checks the callback break counters and cancels the
callback promise if they changed during the operation.
[*] Note that "callback break counters" are counters of server
events that cancel one or more callback promises that the client
thinks it has. The client counts the events and compares the
counters before and after an operation to see if the callback
promise it thinks it just got evaporated before it got recorded
under lock.
- Volume and server callback break counters are passed into
afs_iget() allowing callback breaks concurrent with inode set up to
be detected and the callback promise thence to be cancelled.
- AFS validation checks are now done under RCU conditions using a
read lock on cb_lock. This requires vnode->cb_interest to be made
RCU safe.
- If the checks in (6) fail, the callback breaker is then called
under write lock on the cb_lock - but only if the callback break
counter didn't change from the value read before the checks were
made.
- Results from FS.InlineBulkStatus that correspond to inodes we
currently have in memory are now used to update those inodes'
status and callback information rather than being discarded. This
requires those inodes to be looked up before the RPC op is made and
all their callback break values saved.
To aid in this, the following changes have also been made:
- Don't pass the vnode into the reply delivery functions or the
decoders. The vnode shouldn't be altered anywhere in those paths.
The only exception, for the moment, is for the call done hook for
file lock ops that wants access to both the vnode and the call -
this can be fixed at a later time.
- Get rid of the call->reply[] void* array and replace it with named
and typed members. This avoids confusion since different ops were
mapping different reply[] members to different things.
- Fix an order-1 kmalloc allocation in afs_do_lookup() and replace it
with kvcalloc().
- Always get the reply time. Since callback, lock and fileserver
record expiry times are calculated for several RPCs, make this
mandatory.
- Call afs_pages_written_back() from the operation wrapper rather
than from the delivery function.
- Don't store the version and type from a callback promise in a reply
as the information in them is of very limited use"
* tag 'afs-fixes-b-20190516' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
afs: Fix application of the results of a inline bulk status fetch
afs: Pass pre-fetch server and volume break counts into afs_iget5_set()
afs: Fix unlink to handle YFS.RemoveFile2 better
afs: Clear AFS_VNODE_CB_PROMISED if we detect callback expiry
afs: Make vnode->cb_interest RCU safe
afs: Split afs_validate() so first part can be used under LOOKUP_RCU
afs: Don't save callback version and type fields
afs: Fix application of status and callback to be under same lock
afs: Always get the reply time
afs: Fix order-1 allocation in afs_do_lookup()
afs: Get rid of afs_call::reply[]
afs: Don't pass the vnode pointer through into the inline bulk status op
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.