kernel/linux.git/fs/netfs/buffered_read.c, branch linux-7.0.y

netfs: Fix the handling of stream->front by removing it

2026-03-26T14:18:45+00:00

The netfs_io_stream::front member is meant to point to the subrequest currently being collected on a stream, but it isn't actually used this way by direct write (which mostly ignores it). However, there's a tracepoint which looks at it. Further, stream->front is actually redundant with stream->subrequests.next. Fix the potential problem in the direct code by just removing the member and using stream->subrequests.next instead, thereby also simplifying the code. Fixes: a0b4c7a49137 ("netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict sequence") Reported-by: Paulo Alcantara Signed-off-by: David Howells Link: https://patch.msgid.link/4158599.1774426817@warthog.procyon.org.uk Reviewed-by: Paulo Alcantara (Red Hat) cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

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

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

This was done entirely with mindless brute force, using git grep -l '\

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

netfs: fix reference leak

2025-09-26T08:14:19+00:00

Commit 20d72b00ca81 ("netfs: Fix the request's work item to not require a ref") modified netfs_alloc_request() to initialize the reference counter to 2 instead of 1. The rationale was that the requet's "work" would release the second reference after completion (via netfs_{read,write}_collection_worker()). That works most of the time if all goes well. However, it leaks this additional reference if the request is released before the I/O operation has been submitted: the error code path only decrements the reference counter once and the work item will never be queued because there will never be a completion. This has caused outages of our whole server cluster today because tasks were blocked in netfs_wait_for_outstanding_io(), leading to deadlocks in Ceph (another bug that I will address soon in another patch). This was caused by a netfs_pgpriv2_begin_copy_to_cache() call which failed in fscache_begin_write_operation(). The leaked netfs_io_request was never completed, leaving `netfs_inode.io_count` with a positive value forever. All of this is super-fragile code. Finding out which code paths will lead to an eventual completion and which do not is hard to see: - Some functions like netfs_create_write_req() allocate a request, but will never submit any I/O. - netfs_unbuffered_read_iter_locked() calls netfs_unbuffered_read() and then netfs_put_request(); however, netfs_unbuffered_read() can also fail early before submitting the I/O request, therefore another netfs_put_request() call must be added there. A rule of thumb is that functions that return a `netfs_io_request` do not submit I/O, and all of their callers must be checked. For my taste, the whole netfs code needs an overhaul to make reference counting easier to understand and less fragile & obscure. But to fix this bug here and now and produce a patch that is adequate for a stable backport, I tried a minimal approach that quickly frees the request object upon early failure. I decided against adding a second netfs_put_request() each time because that would cause code duplication which obscures the code further. Instead, I added the function netfs_put_failed_request() which frees such a failed request synchronously under the assumption that the reference count is exactly 2 (as initially set by netfs_alloc_request() and never touched), verified by a WARN_ON_ONCE(). It then deinitializes the request object (without going through the "cleanup_work" indirection) and frees the allocation (with RCU protection to protect against concurrent access by netfs_requests_seq_start()). All code paths that fail early have been changed to call netfs_put_failed_request() instead of netfs_put_request(). Additionally, I have added a netfs_put_request() call to netfs_unbuffered_read() as explained above because the netfs_put_failed_request() approach does not work there. Fixes: 20d72b00ca81 ("netfs: Fix the request's work item to not require a ref") Signed-off-by: Max Kellermann Signed-off-by: David Howells cc: Paulo Alcantara cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org cc: stable@vger.kernel.org Signed-off-by: Christian Brauner

Merge patch series "netfs: Miscellaneous fixes"

2025-05-21T12:35:34+00:00

David Howells says: Here are some miscellaneous fixes and changes for netfslib, if you could pull them: (1) Fix an oops in write-retry due to mis-resetting the I/O iterator. (2) Fix the recording of transferred bytes for short DIO reads. (3) Fix a request's work item to not require a reference, thereby avoiding the need to get rid of it in BH/IRQ context. (4) Fix waiting and waking to be consistent about the waitqueue used. * patches from https://lore.kernel.org/20250519090707.2848510-1-dhowells@redhat.com: netfs: Fix wait/wake to be consistent about the waitqueue used netfs: Fix the request's work item to not require a ref netfs: Fix setting of transferred bytes with short DIO reads netfs: Fix oops in write-retry from mis-resetting the subreq iterator Link: https://lore.kernel.org/20250519090707.2848510-1-dhowells@redhat.com Signed-off-by: Christian Brauner

netfs: Fix wait/wake to be consistent about the waitqueue used

2025-05-21T12:35:21+00:00

Fix further inconsistencies in the use of waitqueues (clear_and_wake_up_bit() vs private waitqueue). Move some of this stuff from the read and write sides into common code so that it can be done in fewer places. To make this work, async I/O needs to set NETFS_RREQ_OFFLOAD_COLLECTION to indicate that a workqueue will do the collecting and places that call the wait function need to deal with it returning the amount transferred. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Signed-off-by: David Howells Link: https://lore.kernel.org/20250519090707.2848510-5-dhowells@redhat.com cc: Marc Dionne cc: Steve French cc: Ihor Solodrai cc: Eric Van Hensbergen cc: Latchesar Ionkov cc: Dominique Martinet cc: Christian Schoenebeck cc: Paulo Alcantara cc: Jeff Layton cc: v9fs@lists.linux.dev cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Fix the request's work item to not require a ref

2025-05-21T12:35:20+00:00

When the netfs_io_request struct's work item is queued, it must be supplied with a ref to the work item struct to prevent it being deallocated whilst on the queue or whilst it is being processed. This is tricky to manage as we have to get a ref before we try and queue it and then we may find it's already queued and is thus already holding a ref - in which case we have to try and get rid of the ref again. The problem comes if we're in BH or IRQ context and need to drop the ref: if netfs_put_request() reduces the count to 0, we have to do the cleanup - but the cleanup may need to wait. Fix this by adding a new work item to the request, ->cleanup_work, and dispatching that when the refcount hits zero. That can then synchronously cancel any outstanding work on the main work item before doing the cleanup. Adding a new work item also deals with another problem upstream where it's sometimes changing the work func in the put function and requeuing it - which has occasionally in the past caused the cleanup to happen incorrectly. As a bonus, this allows us to get rid of the 'was_async' parameter from a bunch of functions. This indicated whether the put function might not be permitted to sleep. Fixes: 3d3c95046742 ("netfs: Provide readahead and readpage netfs helpers") Signed-off-by: David Howells Link: https://lore.kernel.org/20250519090707.2848510-4-dhowells@redhat.com cc: Paulo Alcantara cc: Marc Dionne cc: Steve French cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

fs/netfs: remove `netfs_io_request.ractl`

2025-05-21T12:34:38+00:00

Since this field is only used by netfs_prepare_read_iterator() when called by netfs_readahead(), we can simply pass it as parameter. This shrinks the struct from 576 to 568 bytes. Signed-off-by: Max Kellermann Signed-off-by: David Howells Link: https://lore.kernel.org/20250519134813.2975312-8-dhowells@redhat.com cc: Paulo Alcantara cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Fix setting NETFS_RREQ_ALL_QUEUED to be after all subreqs queued

2025-02-13T15:00:48+00:00

Due to the code that queues a subreq on the active subrequest list getting moved to netfs_issue_read(), the NETFS_RREQ_ALL_QUEUED flag may now get set before the list-add actually happens. This is not a problem if the collection worker happens after the list-add, but it's a race - and, for 9P, where the read from the server is synchronous and done in the submitting thread, this is a lot more likely. The result is that, if the timing is wrong, a ref gets leaked because the collector thinks that all the subreqs have completed (because it can't see the last one yet) and clears NETFS_RREQ_IN_PROGRESS - at which point, the collection worker no longer goes into the collector. This can be provoked with AFS by injecting an msleep() right before the final subreq is queued. Fix this by splitting the queuing part out of netfs_issue_read() into a new function, netfs_queue_read(), and calling it separately. The setting of NETFS_RREQ_ALL_QUEUED is then done by netfs_queue_read() whilst it is holding the spinlock (that's probably unnecessary, but shouldn't hurt). It might be better to set a flag on the final subreq, but this could be a problem if an error occurs and we can't queue it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reported-by: Ihor Solodrai Closes: https://lore.kernel.org/r/a7x33d4dnMdGTtRivptq6S1i8btK70SNBP2XyX_xwDAhLvgQoPox6FVBOkifq4eBinfFfbZlIkMZBe3QarlWTxoEtHZwJCZbNKtaqrR7PvI=@pm.me/ Signed-off-by: David Howells Link: https://lore.kernel.org/r/20250212222402.3618494-4-dhowells@redhat.com Tested-by: Ihor Solodrai cc: Eric Van Hensbergen cc: Latchesar Ionkov cc: Dominique Martinet cc: Christian Schoenebeck cc: Marc Dionne cc: Steve French cc: Paulo Alcantara cc: Jeff Layton cc: v9fs@lists.linux.dev cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

afs: Locally initialise the contents of a new symlink on creation

2024-12-20T21:34:09+00:00

Since we know what the contents of a symlink will be when we create it on the server, initialise its contents locally too to avoid the need to download it. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-31-dhowells@redhat.com cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Christian Brauner