__dax_dbg() currently assumes that bh->b_bdev is non-NULL, passing it into bdevname() where is is dereferenced. This assumption isn't always true - when called for reads of holes, ext4_dax_mmap_get_block() returns a buffer head where bh->b_bdev is never set. I hit this BUG while testing the DAX PMD fault path.
Instead, verify that we have a valid bh->b_bdev, else just say "unknown" for the block device. Signed-off-by: Ross Zwisler <[email protected]> Cc: Dan Williams <[email protected]> --- fs/dax.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/dax.c b/fs/dax.c index 7af8797..03cc4a3 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -563,7 +563,12 @@ static void __dax_dbg(struct buffer_head *bh, unsigned long address, { if (bh) { char bname[BDEVNAME_SIZE]; - bdevname(bh->b_bdev, bname); + + if (bh->b_bdev) + bdevname(bh->b_bdev, bname); + else + snprintf(bname, BDEVNAME_SIZE, "unknown"); + pr_debug("%s: %s addr: %lx dev %s state %lx start %lld " "length %zd fallback: %s\n", fn, current->comm, address, bname, bh->b_state, (u64)bh->b_blocknr, -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
