kernel.git/fs/netfs/buffered_read.c, branch linux-6.15.y

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

2025-06-19T13:40:21Z

[ Upstream commit 2b1424cd131cfaba4cf7040473133d26cddac088 ] 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 Signed-off-by: Sasha Levin

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

2025-06-19T13:40:21Z

[ Upstream commit 20d72b00ca814d748f5663484e5c53bb2bf37a3a ] 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 Signed-off-by: Sasha Levin

netfs: Fix setting NETFS_RREQ_ALL_QUEUED to be after all subreqs queued

2025-02-13T15:00:48Z

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

2024-12-20T21:34:09Z

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

netfs: Change the read result collector to only use one work item

2024-12-20T21:34:08Z

Change the way netfslib collects read results to do all the collection for a particular read request using a single work item that walks along the subrequest queue as subrequests make progress or complete, unlocking folios progressively rather than doing the unlock in parallel as parallel requests come in. The code is remodelled to be more like the write-side code, though only using a single stream. This makes it more directly comparable and thus easier to duplicate fixes between the two sides. This has a number of advantages: (1) It's simpler. There doesn't need to be a complex donation mechanism to handle mismatches between the size and alignment of subrequests and folios. The collector unlocks folios as the subrequests covering each complete. (2) It should cause less scheduler overhead as there's a single work item in play unlocking pages in parallel when a read gets split up into a lot of subrequests instead of one per subrequest. Whilst the parallellism is nice in theory, in practice, the vast majority of loads are sequential reads of the whole file, so committing a bunch of threads to unlocking folios out of order doesn't help in those cases. (3) It should make it easier to implement content decryption. A folio cannot be decrypted until all the requests that contribute to it have completed - and, again, most loads are sequential and so, most of the time, we want to begin decryption sequentially (though it's great if the decryption can happen in parallel). There is a disadvantage in that we're losing the ability to decrypt and unlock things on an as-things-arrive basis which may affect some applications. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-28-dhowells@redhat.com cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Add support for caching single monolithic objects such as AFS dirs

2024-12-20T21:34:06Z

Add support for caching the content of a file that contains a single monolithic object that must be read/written with a single I/O operation, such as an AFS directory. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-20-dhowells@redhat.com cc: Jeff Layton cc: Marc Dionne cc: netfs@lists.linux.dev cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Don't use bh spinlock

2024-12-20T21:34:04Z

All the accessing of the subrequest lists is now done in process context, possibly in a workqueue, but not now in a BH context, so we don't need the lock against BH interference when taking the netfs_io_request::lock spinlock. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-11-dhowells@redhat.com cc: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Signed-off-by: Christian Brauner

netfs: Drop the was_async arg from netfs_read_subreq_terminated()

2024-12-20T21:34:03Z

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: Drop the error arg from netfs_read_subreq_terminated()

2024-12-20T21:34:03Z

Drop the error argument from netfs_read_subreq_terminated() in favour of passing the value in subreq->error. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-9-dhowells@redhat.com cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Abstract out a rolling folio buffer implementation

2024-12-20T21:34:02Z

A rolling buffer is a series of folios held in a list of folio_queues. New folios and folio_queue structs may be inserted at the head simultaneously with spent ones being removed from the tail without the need for locking. The rolling buffer includes an iov_iter and it has to be careful managing this as the list of folio_queues is extended such that an oops doesn't incurred because the iterator was pointing to the end of a folio_queue segment that got appended to and then removed. We need to use the mechanism twice, once for read and once for write, and, in future patches, we will use a second rolling buffer to handle bounce buffering for content encryption. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-6-dhowells@redhat.com cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner