On Fri, Feb 23, 2024 at 9:15 AM David Howells <dhowells@xxxxxxxxxx> wrote: > > > If a directory has a block with only ".__afsXXXX" files in it (from > uncompleted silly-rename), these .__afsXXXX files are skipped but without > advancing the file position in the dir_context. This leads to > afs_dir_iterate() repeating the block again and again. > > Fix this by making the code that skips the .__afsXXXX file also manually > advance the file position. > > The symptoms are a soft lookup: > > watchdog: BUG: soft lockup - CPU#3 stuck for 52s! [check:5737] > ... > RIP: 0010:afs_dir_iterate_block+0x39/0x1fd > ... > ? watchdog_timer_fn+0x1a6/0x213 > ... > ? asm_sysvec_apic_timer_interrupt+0x16/0x20 > ? afs_dir_iterate_block+0x39/0x1fd > afs_dir_iterate+0x10a/0x148 > afs_readdir+0x30/0x4a > iterate_dir+0x93/0xd3 > __do_sys_getdents64+0x6b/0xd4 > > This is almost certainly the actual fix for: > > https://bugzilla.kernel.org/show_bug.cgi?id=218496 > > Fixes: 57e9d49c5452 ("afs: Hide silly-rename files from userspace") > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > cc: Marc Dionne <marc.dionne@xxxxxxxxxxxx> > cc: Markus Suvanto <markus.suvanto@xxxxxxxxx> > cc: linux-afs@xxxxxxxxxxxxxxxxxxx > --- > fs/afs/dir.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/afs/dir.c b/fs/afs/dir.c > index b5b8de521f99..8a67fc427e74 100644 > --- a/fs/afs/dir.c > +++ b/fs/afs/dir.c > @@ -479,8 +479,10 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode, > dire->u.name[0] == '.' && > ctx->actor != afs_lookup_filldir && > ctx->actor != afs_lookup_one_filldir && > - memcmp(dire->u.name, ".__afs", 6) == 0) > + memcmp(dire->u.name, ".__afs", 6) == 0) { > + ctx->pos = blkoff + next * sizeof(union afs_xdr_dirent); > continue; > + } > > /* found the next entry */ > if (!dir_emit(ctx, dire->u.name, nlen, Reviewed-by: Marc Dionne <marc.dionne@xxxxxxxxxxxx> Marc
