ocfs2: Allow smaller allocations during large writes

The ocfs2 write code loops through a page much like the block code, except
that ocfs2 allocation units can be any size, including larger than page
size. Typically it's equal to or larger than page size - most kernels run 4k
pages, the minimum ocfs2 allocation (cluster) size.

Some changes introduced during 2.6.23 changed the way writes to pages are
handled, and inadvertantly broke support for > 4k page size. Instead of just
writing one cluster at a time, we now handle the whole page in one pass.

This means that multiple (small) seperate allocations might happen in the
same pass. The allocation code howver typically optimizes by getting the
maximum which was reserved. This triggered a BUG_ON in the extend code where
it'd ask for a single bit (for one part of a > 4k page) and get back more
than it asked for.

Fix this by providing a variant of the high level allocation function which
allows the caller to specify a maximum. The traditional function remains and
just calls the new one with a maximum determined from the initial
reservation.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/fs/ocfs2/localalloc.c b/fs/ocfs2/localalloc.c
index 545f7892cdf3..de984d272576 100644
--- a/fs/ocfs2/localalloc.c
+++ b/fs/ocfs2/localalloc.c
@@ -524,13 +524,12 @@ bail:
 int ocfs2_claim_local_alloc_bits(struct ocfs2_super *osb,
                                  handle_t *handle,
                                  struct ocfs2_alloc_context *ac,
-                                 u32 min_bits,
+                                 u32 bits_wanted,
                                  u32 *bit_off,
                                  u32 *num_bits)
 {
         int status, start;
         struct inode *local_alloc_inode;
-        u32 bits_wanted;
         void *bitmap;
         struct ocfs2_dinode *alloc;
         struct ocfs2_local_alloc *la;
@@ -538,7 +537,6 @@ int ocfs2_claim_local_alloc_bits(struct ocfs2_super *osb,
         mlog_entry_void();
         BUG_ON(ac->ac_which != OCFS2_AC_USE_LOCAL);
 
-        bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;
         local_alloc_inode = ac->ac_inode;
         alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
         la = OCFS2_LOCAL_ALLOC(alloc);