kernel/linux.git/fs/afs/fsclient.c, branch v7.1

afs: Fix the locking used by afs_get_link()

2026-05-12T12:42:33+00:00

The afs filesystem in the kernel doesn't do locking correctly for symbolic links. There are a number of problems: (1) It doesn't do any locking around afs_read_single() to prevent races between multiple ->get_link() calls, thereby allowing the possibility of leaks. (2) It doesn't use RCU barriering when accessing the buffer pointers during RCU pathwalk. (3) It can race with another thread updating the contents of the symlink if a third party updated it on the server. Fix this by the following means: (0) Move symlink handling into its own file as this makes it more complicated. (1) Take the validate_lock around afs_read_single() to prevent races between multiple ->get_link() calls. (2) Keep a separate copy of the symlink contents with an rcu_head. This is always going to be a lot smaller than a page, so it can be kmalloc'd and save quite a bit of memory. It also needs a refcount for non-RCU pathwalk. (3) Split the symlink read and write-to-cache routines in afs from those for directories. (4) Discard the I/O buffer as soon as the write-to-cache completes as this is a full page (plus a folio_queue). (5) If there's no cache, discard the I/O buffer immediately after reading and copying if there is no cache. Fixes: eae9e78951bb ("afs: Use netfslib for symlinks, allowing them to be cached") Fixes: 6698c02d64b2 ("afs: Locally initialise the contents of a new symlink on creation") Closes: https://sashiko.dev/#/patchset/20260326104544.509518-1-dhowells%40redhat.com Signed-off-by: David Howells Link: https://patch.msgid.link/20260512123404.719402-25-dhowells@redhat.com cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

Convert 'alloc_flex' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This is the exact same thing as the 'alloc_obj()' version, only much smaller because there are a lot fewer users of the *alloc_flex() interface. As with alloc_obj() version, this was done entirely with mindless brute force, using the same script, except using 'flex' in the pattern rather than 'objs*'. Signed-off-by: Linus Torvalds

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

afs: Fix afs_server ref accounting

2025-03-10T09:47:15+00:00

The current way that afs_server refs are accounted and cleaned up sometimes cause rmmod to hang when it is waiting for cell records to be removed. The problem is that the cell cleanup might occasionally happen before the server cleanup and then there's nothing that causes the cell to garbage-collect the remaining servers as they become inactive. Partially fix this by: (1) Give each afs_server record its own management timer that rather than relying on the cell manager's central timer to drive each individual cell's maintenance work item to garbage collect servers. This timer is set when afs_unuse_server() reduces a server's activity count to zero and will schedule the server's destroyer work item upon firing. (2) Give each afs_server record its own destroyer work item that removes the record from the cell's database, shuts down the timer, cancels any pending work for itself, sends an RPC to the server to cancel outstanding callbacks. This change, in combination with the timer, obviates the need to try and coordinate so closely between the cell record and a bunch of other server records to try and tear everything down in a coordinated fashion. With this, the cell record is pinned until the server RCU is complete and namespace/module removal will wait until all the cell records are removed. (3) Now that incoming calls are mapped to servers (and thus cells) using data attached to an rxrpc_peer, the UUID-to-server mapping tree is moved from the namespace to the cell (cell->fs_servers). This means there can no longer be duplicates therein - and that allows the mapping tree to be simpler as there doesn't need to be a chain of same-UUID servers that are in different cells. (4) The lock protecting the UUID mapping tree is switched to an rw_semaphore on the cell rather than a seqlock on the namespace as it's now only used during mounting in contexts in which we're allowed to sleep. (5) When it comes time for a cell that is being removed to purge its set of servers, it just needs to iterate over them and wake them up. Once a server becomes inactive, its destroyer work item will observe the state of the cell and immediately remove that record. (6) When a server record is removed, it is marked AFS_SERVER_FL_EXPIRED to prevent reattempts at removal. The record will be dispatched to RCU for destruction once its refcount reaches 0. (7) The AFS_SERVER_FL_UNCREATED/CREATING flags are used to synchronise simultaneous creation attempts. If one attempt fails, it will abandon the attempt and allow another to try again. Note that the record can't just be abandoned when dead as it's bound into a server list attached to a volume and only subject to replacement if the server list obtained for the volume from the VLDB changes. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-15-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-11-dhowells@redhat.com/ # v4

afs: Improve server refcount/active count tracing

2025-03-10T09:47:15+00:00

Improve server refcount/active count tracing to distinguish between simply getting/putting a ref and using/unusing the server record (which changes the activity count as well as the refcount). This makes it a bit easier to work out what's going on. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-10-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-6-dhowells@redhat.com/ # v4

afs: Make {Y,}FS.FetchData an asynchronous operation

2024-12-20T21:34:08+00:00

Make FS.FetchData and YFS.FetchData an asynchronous operation in that the request is queued in AF_RXRPC and then we return to the caller rather than waiting. Processing of the returning packets is then done inline if it's a synchronous VFS/VM call (readdir, read_folio, sync DIO, prep for write) or offloaded to a workqueue if asynchronous VM calls (eg. readahead, async DIO). This reduces the chain of workqueues invoking workqueues and cuts out some of the overhead, driving rxrpc data extraction and netfslib read collection from a thread that's going to block to completion anyway if possible. The ->done() call op is also split with ->immediate_cancel() handling the cancellation on failure to begin the call and ->done() handling the rest. This means that the AFS async FetchData code doesn't try to terminate the netfs subrequest twice. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-26-dhowells@redhat.com cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Christian Brauner

afs: Eliminate afs_read

2024-12-20T21:34:07+00:00

Now that directory and symlink reads go through netfslib, the afs_read struct is mostly redundant with almost all data duplicated in the netfs_io_request and netfs_io_subrequest structs that are also available any time we're doing a fetch. Eliminate afs_read by moving the one field we still need there to the afs_call struct (we may be given a different amount of data than what we asked for and have to track what remains of that) and using the netfs_io_subrequest directly instead. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-24-dhowells@redhat.com cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Christian Brauner

netfs: Drop the was_async arg from netfs_read_subreq_terminated()

2024-12-20T21:34:03+00:00

Drop the was_async argument from netfs_read_subreq_terminated(). Almost every caller is either in process context and passes false. Some filesystems delegate the call to a workqueue to avoid doing the work in their network message queue parsing thread. The only exception is netfs_cache_read_terminated() which handles completion in the cache - which is usually a callback from the backing filesystem in softirq context, though it can be from process context if an error occurred. In this case, delegate to a workqueue. Suggested-by: Linus Torvalds Link: https://lore.kernel.org/r/CAHk-=wiVC5Cgyz6QKXFu6fTaA6h4CjexDR-OV9kL6Vo5x9v8=A@mail.gmail.com/ Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-10-dhowells@redhat.com cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Speed up buffered reading

2024-09-12T10:20:41+00:00

Improve the efficiency of buffered reads in a number of ways: (1) Overhaul the algorithm in general so that it's a lot more compact and split the read submission code between buffered and unbuffered versions. The unbuffered version can be vastly simplified. (2) Read-result collection is handed off to a work queue rather than being done in the I/O thread. Multiple subrequests can be processes simultaneously. (3) When a subrequest is collected, any folios it fully spans are collected and "spare" data on either side is donated to either the previous or the next subrequest in the sequence. Notes: (*) Readahead expansion is massively slows down fio, presumably because it causes a load of extra allocations, both folio and xarray, up front before RPC requests can be transmitted. (*) RDMA with cifs does appear to work, both with SIW and RXE. (*) PG_private_2-based reading and copy-to-cache is split out into its own file and altered to use folio_queue. Note that the copy to the cache now creates a new write transaction against the cache and adds the folios to be copied into it. This allows it to use part of the writeback I/O code. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-20-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

afs: trace: Log afs_make_call(), including server address

2024-01-01T16:37:27+00:00

Add a tracepoint to log calls to afs_make_call(), including the destination server address. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org