Dave Wysochanski df1c357f25 netfs: Only call folio_start_fscache() one time for each folio ... 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>		2023-09-18 12:03:46 -07:00
..
buffered_read.c	netfs: Only call folio_start_fscache() one time for each folio	2023-09-18 12:03:46 -07:00
internal.h
io.c
iterator.c
Kconfig
main.c
Makefile
objects.c
stats.c