ocfs2: move nonsparse hole-filling into ocfs2_write_begin()

By doing this, we can remove any higher level logic which has to have
knowledge of btree functionality - any callers of ocfs2_write_begin() can
now expect it to do anything necessary to prepare the inode for new data.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Reviewed-by: Joel Becker <joel.becker@oracle.com>

3 files changed, 115 insertions, 144 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index f37f25c931..fae07672eb 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -301,12 +301,8 @@ int ocfs2_prepare_write_nolock(struct inode *inode, struct page *page,
 {
         int ret;
 
-        down_read(&OCFS2_I(inode)->ip_alloc_sem);
-
         ret = block_prepare_write(page, from, to, ocfs2_get_block);
 
-        up_read(&OCFS2_I(inode)->ip_alloc_sem);
-
         return ret;
 }
 
@@ -1360,6 +1356,36 @@ out:
         return ret;
 }
 
+/*
+ * This function only does anything for file systems which can't
+ * handle sparse files.
+ *
+ * What we want to do here is fill in any hole between the current end
+ * of allocation and the end of our write. That way the rest of the
+ * write path can treat it as an non-allocating write, which has no
+ * special case code for sparse/nonsparse files.
+ */
+static int ocfs2_expand_nonsparse_inode(struct inode *inode, loff_t pos,
+                                        unsigned len,
+                                        struct ocfs2_write_ctxt *wc)
+{
+        int ret;
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        loff_t newsize = pos + len;
+
+        if (ocfs2_sparse_alloc(osb))
+                return 0;
+
+        if (newsize <= i_size_read(inode))
+                return 0;
+
+        ret = ocfs2_extend_no_holes(inode, newsize, newsize - len);
+        if (ret)
+                mlog_errno(ret);
+
+        return ret;
+}
+
 int ocfs2_write_begin_nolock(struct address_space *mapping,
                              loff_t pos, unsigned len, unsigned flags,
                              struct page **pagep, void **fsdata,
@@ -1381,6 +1407,12 @@ int ocfs2_write_begin_nolock(struct address_space *mapping,
                 return ret;
         }
 
+        ret = ocfs2_expand_nonsparse_inode(inode, pos, len, wc);
+        if (ret) {
+                mlog_errno(ret);
+                goto out;
+        }
+
         ret = ocfs2_populate_write_desc(inode, wc, &clusters_to_alloc,
                                         &extents_to_split);
         if (ret) {
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index f3bc3658e7..781ba6c4ef 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -779,25 +779,6 @@ leave:
         return status;
 }
 
-static int ocfs2_extend_allocation(struct inode *inode, u32 logical_start,
-                                   u32 clusters_to_add, int mark_unwritten)
-{
-        int ret;
-
-        /*
-         * The alloc sem blocks peope in read/write from reading our
-         * allocation until we're done changing it. We depend on
-         * i_mutex to block other extend/truncate calls while we're
-         * here.
-         */
-        down_write(&OCFS2_I(inode)->ip_alloc_sem);
-        ret = __ocfs2_extend_allocation(inode, logical_start, clusters_to_add,
-                                        mark_unwritten);
-        up_write(&OCFS2_I(inode)->ip_alloc_sem);
-
-        return ret;
-}
-
 /* Some parts of this taken from generic_cont_expand, which turned out
  * to be too fragile to do exactly what we need without us having to
  * worry about recursive locking in ->prepare_write() and
@@ -889,25 +870,47 @@ out:
         return ret;
 }
 
-/* 
- * A tail_to_skip value > 0 indicates that we're being called from
- * ocfs2_file_aio_write(). This has the following implications:
- *
- * - we don't want to update i_size
- * - di_bh will be NULL, which is fine because it's only used in the
- *   case where we want to update i_size.
- * - ocfs2_zero_extend() will then only be filling the hole created
- *   between i_size and the start of the write.
- */
+int ocfs2_extend_no_holes(struct inode *inode, u64 new_i_size, u64 zero_to)
+{
+        int ret;
+        u32 clusters_to_add;
+        struct ocfs2_inode_info *oi = OCFS2_I(inode);
+
+        clusters_to_add = ocfs2_clusters_for_bytes(inode->i_sb, new_i_size);
+        if (clusters_to_add < oi->ip_clusters)
+                clusters_to_add = 0;
+        else
+                clusters_to_add -= oi->ip_clusters;
+
+        if (clusters_to_add) {
+                ret = __ocfs2_extend_allocation(inode, oi->ip_clusters,
+                                                clusters_to_add, 0);
+                if (ret) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+        }
+
+        /*
+         * Call this even if we don't add any clusters to the tree. We
+         * still need to zero the area between the old i_size and the
+         * new i_size.
+         */
+        ret = ocfs2_zero_extend(inode, zero_to);
+        if (ret < 0)
+                mlog_errno(ret);
+
+out:
+        return ret;
+}
+
 static int ocfs2_extend_file(struct inode *inode,
                              struct buffer_head *di_bh,
-                             u64 new_i_size,
-                             size_t tail_to_skip)
+                             u64 new_i_size)
 {
         int ret = 0;
-        u32 clusters_to_add = 0;
 
-        BUG_ON(!tail_to_skip && !di_bh);
+        BUG_ON(!di_bh);
 
         /* setattr sometimes calls us like this. */
         if (new_i_size == 0)
@@ -917,13 +920,8 @@ static int ocfs2_extend_file(struct inode *inode,
                 goto out;
         BUG_ON(new_i_size < i_size_read(inode));
 
-        if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
-                BUG_ON(tail_to_skip != 0);
+        if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
                 goto out_update_size;
-        }
-
-        clusters_to_add = ocfs2_clusters_for_bytes(inode->i_sb, new_i_size) - 
-                OCFS2_I(inode)->ip_clusters;
 
         /* 
          * protect the pages that ocfs2_zero_extend is going to be
@@ -938,35 +936,25 @@ static int ocfs2_extend_file(struct inode *inode,
                 goto out;
         }
 
-        if (clusters_to_add) {
-                ret = ocfs2_extend_allocation(inode,
-                                              OCFS2_I(inode)->ip_clusters,
-                                              clusters_to_add, 0);
-                if (ret < 0) {
-                        mlog_errno(ret);
-                        goto out_unlock;
-                }
-        }
-
         /*
-         * Call this even if we don't add any clusters to the tree. We
-         * still need to zero the area between the old i_size and the
-         * new i_size.
+         * The alloc sem blocks people in read/write from reading our
+         * allocation until we're done changing it. We depend on
+         * i_mutex to block other extend/truncate calls while we're
+         * here.
          */
-        ret = ocfs2_zero_extend(inode, (u64)new_i_size - tail_to_skip);
+        down_write(&OCFS2_I(inode)->ip_alloc_sem);
+        ret = ocfs2_extend_no_holes(inode, new_i_size, new_i_size);
+        up_write(&OCFS2_I(inode)->ip_alloc_sem);
+
         if (ret < 0) {
                 mlog_errno(ret);
                 goto out_unlock;
         }
 
 out_update_size:
-        if (!tail_to_skip) {
-                /* We're being called from ocfs2_setattr() which wants
-                 * us to update i_size */
-                ret = ocfs2_simple_size_update(inode, di_bh, new_i_size);
-                if (ret < 0)
-                        mlog_errno(ret);
-        }
+        ret = ocfs2_simple_size_update(inode, di_bh, new_i_size);
+        if (ret < 0)
+                mlog_errno(ret);
 
 out_unlock:
         if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
@@ -1035,7 +1023,7 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
                 if (i_size_read(inode) > attr->ia_size)
                         status = ocfs2_truncate_file(inode, bh, attr->ia_size);
                 else
-                        status = ocfs2_extend_file(inode, bh, attr->ia_size, 0);
+                        status = ocfs2_extend_file(inode, bh, attr->ia_size);
                 if (status < 0) {
                         if (status != -ENOSPC)
                                 mlog_errno(status);
@@ -1713,15 +1701,13 @@ static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
                                          int appending,
                                          int *direct_io)
 {
-        int ret = 0, meta_level = appending;
+        int ret = 0, meta_level = 0;
         struct inode *inode = dentry->d_inode;
-        u32 clusters;
-        loff_t newsize, saved_pos;
+        loff_t saved_pos, end;
 
         /* 
-         * We sample i_size under a read level meta lock to see if our write
-         * is extending the file, if it is we back off and get a write level
-         * meta lock.
+         * We start with a read level meta lock and only jump to an ex
+         * if we need to make modifications here.
          */
         for(;;) {
                 ret = ocfs2_meta_lock(inode, NULL, meta_level);
@@ -1763,87 +1749,38 @@ static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
                         saved_pos = *ppos;
                 }
 
-                if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
-                        loff_t end = saved_pos + count;
-
-                        /*
-                         * Skip the O_DIRECT checks if we don't need
-                         * them.
-                         */
-                        if (!direct_io || !(*direct_io))
-                                break;
-
-                        /*
-                         * Allowing concurrent direct writes means
-                         * i_size changes wouldn't be synchronized, so
-                         * one node could wind up truncating another
-                         * nodes writes.
-                         */
-                        if (end > i_size_read(inode)) {
-                                *direct_io = 0;
-                                break;
-                        }
+                end = saved_pos + count;
 
-                        /*
-                         * We don't fill holes during direct io, so
-                         * check for them here. If any are found, the
-                         * caller will have to retake some cluster
-                         * locks and initiate the io as buffered.
-                         */
-                        ret = ocfs2_check_range_for_holes(inode, saved_pos,
-                                                          count);
-                        if (ret == 1) {
-                                *direct_io = 0;
-                                ret = 0;
-                        } else if (ret < 0)
-                                mlog_errno(ret);
+                /*
+                 * Skip the O_DIRECT checks if we don't need
+                 * them.
+                 */
+                if (!direct_io || !(*direct_io))
                         break;
-                }
 
                 /*
-                 * The rest of this loop is concerned with legacy file
-                 * systems which don't support sparse files.
+                 * Allowing concurrent direct writes means
+                 * i_size changes wouldn't be synchronized, so
+                 * one node could wind up truncating another
+                 * nodes writes.
                  */
-
-                newsize = count + saved_pos;
-
-                mlog(0, "pos=%lld newsize=%lld cursize=%lld\n",
-                     (long long) saved_pos, (long long) newsize,
-                     (long long) i_size_read(inode));
-
-                /* No need for a higher level metadata lock if we're
-                 * never going past i_size. */
-                if (newsize <= i_size_read(inode))
+                if (end > i_size_read(inode)) {
+                        *direct_io = 0;
                         break;
-
-                if (meta_level == 0) {
-                        ocfs2_meta_unlock(inode, meta_level);
-                        meta_level = 1;
-                        continue;
                 }
 
-                spin_lock(&OCFS2_I(inode)->ip_lock);
-                clusters = ocfs2_clusters_for_bytes(inode->i_sb, newsize) -
-                        OCFS2_I(inode)->ip_clusters;
-                spin_unlock(&OCFS2_I(inode)->ip_lock);
-
-                mlog(0, "Writing at EOF, may need more allocation: "
-                     "i_size = %lld, newsize = %lld, need %u clusters\n",
-                     (long long) i_size_read(inode), (long long) newsize,
-                     clusters);
-
-                /* We only want to continue the rest of this loop if
-                 * our extend will actually require more
-                 * allocation. */
-                if (!clusters)
-                        break;
-
-                ret = ocfs2_extend_file(inode, NULL, newsize, count);
-                if (ret < 0) {
-                        if (ret != -ENOSPC)
-                                mlog_errno(ret);
-                        goto out_unlock;
-                }
+                /*
+                 * We don't fill holes during direct io, so
+                 * check for them here. If any are found, the
+                 * caller will have to retake some cluster
+                 * locks and initiate the io as buffered.
+                 */
+                ret = ocfs2_check_range_for_holes(inode, saved_pos, count);
+                if (ret == 1) {
+                        *direct_io = 0;
+                        ret = 0;
+                } else if (ret < 0)
+                        mlog_errno(ret);
                 break;
         }
 
diff --git a/fs/ocfs2/file.h b/fs/ocfs2/file.h
index 36fe27f268..066f14add3 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -47,6 +47,8 @@ int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
                                struct ocfs2_alloc_context *data_ac,
                                struct ocfs2_alloc_context *meta_ac,
                                enum ocfs2_alloc_restarted *reason_ret);
+int ocfs2_extend_no_holes(struct inode *inode, u64 new_i_size,
+                          u64 zero_to);
 int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
                           u32 clusters_to_add, u32 extents_to_split,
                           struct ocfs2_alloc_context **data_ac,