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

netfs: Fix undifferentiation of DIO reads from unbuffered reads

2025-06-19T13:40:21Z

[ Upstream commit db26d62d79e4068934ad0dccdb92715df36352b9 ] On cifs, "DIO reads" (specified by O_DIRECT) need to be differentiated from "unbuffered reads" (specified by cache=none in the mount parameters). The difference is flagged in the protocol and the server may behave differently: Windows Server will, for example, mandate that DIO reads are block aligned. Fix this by adding a NETFS_UNBUFFERED_READ to differentiate this from NETFS_DIO_READ, parallelling the write differentiation that already exists. cifs will then do the right thing. Fixes: 016dc8516aec ("netfs: Implement unbuffered/DIO read support") Signed-off-by: David Howells Link: https://lore.kernel.org/3444961.1747987072@warthog.procyon.org.uk Reviewed-by: "Paulo Alcantara (Red Hat)" Reviewed-by: Viacheslav Dubeyko cc: Steve French cc: netfs@lists.linux.dev cc: v9fs@lists.linux.dev cc: linux-afs@lists.infradead.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: linux-nfs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

netfs: Only create /proc/fs/netfs with CONFIG_PROC_FS

2025-04-11T13:58:18Z

When testing a special config: CONFIG_NETFS_SUPPORTS=y CONFIG_PROC_FS=n The system crashes with something like: [ 3.766197] ------------[ cut here ]------------ [ 3.766484] kernel BUG at mm/mempool.c:560! [ 3.766789] Oops: invalid opcode: 0000 [#1] SMP NOPTI [ 3.767123] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W [ 3.767777] Tainted: [W]=WARN [ 3.767968] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), [ 3.768523] RIP: 0010:mempool_alloc_slab.cold+0x17/0x19 [ 3.768847] Code: 50 fe ff 58 5b 5d 41 5c 41 5d 41 5e 41 5f e9 93 95 13 00 [ 3.769977] RSP: 0018:ffffc90000013998 EFLAGS: 00010286 [ 3.770315] RAX: 000000000000002f RBX: ffff888100ba8640 RCX: 0000000000000000 [ 3.770749] RDX: 0000000000000000 RSI: 0000000000000003 RDI: 00000000ffffffff [ 3.771217] RBP: 0000000000092880 R08: 0000000000000000 R09: ffffc90000013828 [ 3.771664] R10: 0000000000000001 R11: 00000000ffffffea R12: 0000000000092cc0 [ 3.772117] R13: 0000000000000400 R14: ffff8881004b1620 R15: ffffea0004ef7e40 [ 3.772554] FS: 0000000000000000(0000) GS:ffff8881b5f3c000(0000) knlGS:0000000000000000 [ 3.773061] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3.773443] CR2: ffffffff830901b4 CR3: 0000000004296001 CR4: 0000000000770ef0 [ 3.773884] PKRU: 55555554 [ 3.774058] Call Trace: [ 3.774232] [ 3.774371] mempool_alloc_noprof+0x6a/0x190 [ 3.774649] ? _printk+0x57/0x80 [ 3.774862] netfs_alloc_request+0x85/0x2ce [ 3.775147] netfs_readahead+0x28/0x170 [ 3.775395] read_pages+0x6c/0x350 [ 3.775623] ? srso_alias_return_thunk+0x5/0xfbef5 [ 3.775928] page_cache_ra_unbounded+0x1bd/0x2a0 [ 3.776247] filemap_get_pages+0x139/0x970 [ 3.776510] ? srso_alias_return_thunk+0x5/0xfbef5 [ 3.776820] filemap_read+0xf9/0x580 [ 3.777054] ? srso_alias_return_thunk+0x5/0xfbef5 [ 3.777368] ? srso_alias_return_thunk+0x5/0xfbef5 [ 3.777674] ? find_held_lock+0x32/0x90 [ 3.777929] ? netfs_start_io_read+0x19/0x70 [ 3.778221] ? netfs_start_io_read+0x19/0x70 [ 3.778489] ? srso_alias_return_thunk+0x5/0xfbef5 [ 3.778800] ? lock_acquired+0x1e6/0x450 [ 3.779054] ? srso_alias_return_thunk+0x5/0xfbef5 [ 3.779379] netfs_buffered_read_iter+0x57/0x80 [ 3.779670] __kernel_read+0x158/0x2c0 [ 3.779927] bprm_execve+0x300/0x7a0 [ 3.780185] kernel_execve+0x10c/0x140 [ 3.780423] ? __pfx_kernel_init+0x10/0x10 [ 3.780690] kernel_init+0xd5/0x150 [ 3.780910] ret_from_fork+0x2d/0x50 [ 3.781156] ? __pfx_kernel_init+0x10/0x10 [ 3.781414] ret_from_fork_asm+0x1a/0x30 [ 3.781677] [ 3.781823] Modules linked in: [ 3.782065] ---[ end trace 0000000000000000 ]--- This is caused by the following error path in netfs_init(): if (!proc_mkdir("fs/netfs", NULL)) goto error_proc; Fix this by adding ifdef in netfs_main(), so that /proc/fs/netfs is only created with CONFIG_PROC_FS. Signed-off-by: Song Liu Link: https://lore.kernel.org/20250409170015.2651829-1-song@kernel.org Acked-by: David Howells 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

afs: Eliminate afs_read

2024-12-20T21:34:07Z

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: 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

Merge tag 'vfs-6.12.netfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-09-16T10:13:31Z

Pull netfs updates from Christian Brauner: "This contains the work to improve read/write performance for the new netfs library. The main performance enhancing changes are: - Define a structure, struct folio_queue, and a new iterator type, ITER_FOLIOQ, to hold a buffer as a replacement for ITER_XARRAY. See that patch for questions about naming and form. ITER_FOLIOQ is provided as a replacement for ITER_XARRAY. The problem with an xarray is that accessing it requires the use of a lock (typically the RCU read lock) - and this means that we can't supply iterate_and_advance() with a step function that might sleep (crypto for example) without having to drop the lock between pages. ITER_FOLIOQ is the iterator for a chain of folio_queue structs, where each folio_queue holds a small list of folios. A folio_queue struct is a simpler structure than xarray and is not subject to concurrent manipulation by the VM. folio_queue is used rather than a bvec[] as it can form lists of indefinite size, adding to one end and removing from the other on the fly. - Provide a copy_folio_from_iter() wrapper. - Make cifs RDMA support ITER_FOLIOQ. - Use folio queues in the write-side helpers instead of xarrays. - Add a function to reset the iterator in a subrequest. - Simplify the write-side helpers to use sheaves to skip gaps rather than trying to work out where gaps are. - In afs, make the read subrequests asynchronous, putting them into work items to allow the next patch to do progressive unlocking/reading. - Overhaul the read-side helpers to improve performance. - Fix the caching of a partial block at the end of a file. - Allow a store to be cancelled. Then some changes for cifs to make it use folio queues instead of xarrays for crypto bufferage: - Use raw iteration functions rather than manually coding iteration when hashing data. - Switch to using folio_queue for crypto buffers. - Remove the xarray bits. Make some adjustments to the /proc/fs/netfs/stats file such that: - All the netfs stats lines begin 'Netfs:' but change this to something a bit more useful. - Add a couple of stats counters to track the numbers of skips and waits on the per-inode writeback serialisation lock to make it easier to check for this as a source of performance loss. Miscellaneous work: - Ensure that the sb_writers lock is taken around vfs_{set,remove}xattr() in the cachefiles code. - Reduce the number of conditional branches in netfs_perform_write(). - Move the CIFS_INO_MODIFIED_ATTR flag to the netfs_inode struct and remove cifs_post_modify(). - Move the max_len/max_nr_segs members from netfs_io_subrequest to netfs_io_request as they're only needed for one subreq at a time. - Add an 'unknown' source value for tracing purposes. - Remove NETFS_COPY_TO_CACHE as it's no longer used. - Set the request work function up front at allocation time. - Use bh-disabling spinlocks for rreq->lock as cachefiles completion may be run from block-filesystem DIO completion in softirq context. - Remove fs/netfs/io.c" * tag 'vfs-6.12.netfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (25 commits) docs: filesystems: corrected grammar of netfs page cifs: Don't support ITER_XARRAY cifs: Switch crypto buffer to use a folio_queue rather than an xarray cifs: Use iterate_and_advance*() routines directly for hashing netfs: Cancel dirty folios that have no storage destination cachefiles, netfs: Fix write to partial block at EOF netfs: Remove fs/netfs/io.c netfs: Speed up buffered reading afs: Make read subreqs async netfs: Simplify the writeback code netfs: Provide an iterator-reset function netfs: Use new folio_queue data type and iterator instead of xarray iter cifs: Provide the capability to extract from ITER_FOLIOQ to RDMA SGEs iov_iter: Provide copy_folio_from_iter() mm: Define struct folio_queue and ITER_FOLIOQ to handle a sequence of folios netfs: Use bh-disabling spinlocks for rreq->lock netfs: Set the request work function upon allocation netfs: Remove NETFS_COPY_TO_CACHE netfs: Reserve netfs_sreq_source 0 as unset/unknown netfs: Move max_len/max_nr_segs from netfs_io_subrequest to netfs_io_stream ...

netfs: Speed up buffered reading

2024-09-12T10:20:41Z

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

netfs: Remove NETFS_COPY_TO_CACHE

2024-09-05T09:00:42Z

Remove NETFS_COPY_TO_CACHE as it isn't used anymore. 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/20240814203850.2240469-10-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Delete subtree of 'fs/netfs' when netfs module exits

2024-08-30T06:22:41Z

In netfs_init() or fscache_proc_init(), we create dentry under 'fs/netfs', but in netfs_exit(), we only delete the proc entry of 'fs/netfs' without deleting its subtree. This triggers the following WARNING: ================================================================== remove_proc_entry: removing non-empty directory 'fs/netfs', leaking at least 'requests' WARNING: CPU: 4 PID: 566 at fs/proc/generic.c:717 remove_proc_entry+0x160/0x1c0 Modules linked in: netfs(-) CPU: 4 UID: 0 PID: 566 Comm: rmmod Not tainted 6.11.0-rc3 #860 RIP: 0010:remove_proc_entry+0x160/0x1c0 Call Trace: netfs_exit+0x12/0x620 [netfs] __do_sys_delete_module.isra.0+0x14c/0x2e0 do_syscall_64+0x4b/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e ================================================================== Therefore use remove_proc_subtree() instead of remove_proc_entry() to fix the above problem. Fixes: 7eb5b3e3a0a5 ("netfs, fscache: Move /proc/fs/fscache to /proc/fs/netfs and put in a symlink") Cc: stable@kernel.org Signed-off-by: Baokun Li Link: https://lore.kernel.org/r/20240826113404.3214786-1-libaokun@huaweicloud.com Acked-by: David Howells Signed-off-by: Christian Brauner

netfs: Revert "netfs: Switch debug logging to pr_debug()"

2024-07-24T08:15:37Z

Revert commit 163eae0fb0d4c610c59a8de38040f8e12f89fd43 to get back the original operation of the debugging macros. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20240608151352.22860-2-ukleinek@kernel.org Link: https://lore.kernel.org/r/1410685.1721333252@warthog.procyon.org.uk cc: Uwe Kleine-König cc: Christian Brauner cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner