Dave Wysochanski df9950d37d netfs: Only call folio_start_fscache() one time for each folio ... [ Upstream commit df1c357f25 ] If a network filesystem using netfs implements a clamp_length() function, it can set subrequest lengths smaller than a page size. When we loop through the folios in netfs_rreq_unlock_folios() to set any folios to be written back, we need to make sure we only call folio_start_fscache() once for each folio. Otherwise, this simple testcase: mount -o fsc,rsize=1024,wsize=1024 127.0.0.1:/export /mnt/nfs dd if=/dev/zero of=/mnt/nfs/file.bin bs=4096 count=1 1+0 records in 1+0 records out 4096 bytes (4.1 kB, 4.0 KiB) copied, 0.0126359 s, 324 kB/s echo 3 > /proc/sys/vm/drop_caches cat /mnt/nfs/file.bin > /dev/null will trigger an oops similar to the following: page dumped because: VM_BUG_ON_FOLIO(folio_test_private_2(folio)) ------------[ cut here ]------------ kernel BUG at include/linux/netfs.h:44! ... CPU: 5 PID: 134 Comm: kworker/u16:5 Kdump: loaded Not tainted 6.4.0-rc5 ... RIP: 0010:netfs_rreq_unlock_folios+0x68e/0x730 [netfs] ... Call Trace: netfs_rreq_assess+0x497/0x660 [netfs] netfs_subreq_terminated+0x32b/0x610 [netfs] nfs_netfs_read_completion+0x14e/0x1a0 [nfs] nfs_read_completion+0x2f9/0x330 [nfs] rpc_free_task+0x72/0xa0 [sunrpc] rpc_async_release+0x46/0x70 [sunrpc] process_one_work+0x3bd/0x710 worker_thread+0x89/0x610 kthread+0x181/0x1c0 ret_from_fork+0x29/0x50 Fixes: 3d3c950467 ("netfs: Provide readahead and readpage netfs helpers" Link: https://bugzilla.redhat.com/show_bug.cgi?id=2210612 Signed-off-by: Dave Wysochanski <dwysocha@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/20230608214137.856006-1-dwysocha@redhat.com/ # v1 Link: https://lore.kernel.org/r/20230915185704.1082982-1-dwysocha@redhat.com/ # v2 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2023-10-06 14:56:32 +02:00
..
Kconfig	netfs: Make CONFIG_NETFS_SUPPORT auto-selected rather than manual	2021-05-25 13:48:04 +01:00
Makefile	netfs: Split some core bits out into their own file	2022-03-18 09:29:05 +00:00
buffered_read.c	netfs: Only call folio_start_fscache() one time for each folio	2023-10-06 14:56:32 +02:00
internal.h	netfs: Fix gcc-12 warning by embedding vfs inode in netfs_i_context	2022-06-09 13:55:00 -07:00
io.c	use less confusing names for iov_iter direction initializers	2023-02-09 11:28:04 +01:00
main.c	netfs: Split some core bits out into their own file	2022-03-18 09:29:05 +00:00
objects.c	netfs: Rename the netfs_io_request cleanup op and give it an op pointer	2022-06-10 20:55:21 +01:00
stats.c	netfs: Add a netfs inode context	2022-03-18 09:29:05 +00:00