ext3: Properly count journal credits for long symlinks

ext3: Properly count journal credits for long symlinks

Commit ae54870a1dc9 ("ext3: Fix lock inversion in ext3_symlink()")
recalculated the number of credits needed for a long symlink, in the
process of splitting it into two transactions.  However, the first
credit calculation under-counted because if selinux is enabled, credits
are needed to create the selinux xattr as well.

Overrunning the reservation will result in an OOPS in
journal_dirty_metadata() due to this assert:

  J_ASSERT_JH(jh, handle->h_buffer_credits > 0);

Fix this by increasing the reservation size.

Signed-off-by: Eric Sandeen <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Acked-by: "Theodore Ts'o" <[email protected]>
Cc: [email protected]
Signed-off-by: Linus Torvalds <[email protected]>