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libnvdimm, btt: fix uninitialized err_lock 

When a sector mode namespace is initially created, the arena's err_lock
is not initialized.  If, on the other hand, the namespace already
exists, the mutex is initialized.  To fix the issue, I moved the mutex
initialization into the arena_alloc, which is called by both
discover_arenas and create_arenas.

This was discovered on an older kernel where mutex_trylock checks the
count to determine whether the lock is held.  Because the data structure
is kzalloc-d, that count was 0 (held), and I/O to the device would hang
forever waiting for the lock to be released (see btt_write_pg, for
example).  Current kernels have a different mutex implementation that
checks for a non-null owner, and so this doesn't show up as a problem.
If that lock were ever contended, it might cause issues, but you'd have
to be really unlucky, I think.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Jeff Moyer 2017-12-13 16:33:09 -05:00 committed by Dan Williams
parent ed07c4338d
commit d08cd5e0eb
1 changed files with 1 additions and 1 deletions
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2
drivers/nvdimm/btt.c
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@ -630,6 +630,7 @@ static struct arena_info *alloc_arena(struct btt *btt, size_t size,
return NULL;
arena->nd_btt = btt->nd_btt;
arena->sector_size = btt->sector_size;
mutex_init(&arena->err_lock);
if (!size)
return arena;
@ -758,7 +759,6 @@ static int discover_arenas(struct btt *btt)
arena->external_lba_start = cur_nlba;
parse_arena_meta(arena, super, cur_off);
mutex_init(&arena->err_lock);
ret = btt_freelist_init(arena);
if (ret)
goto out;