ocfs2: support for removing file regions

Provide an internal interface for the removal of arbitrary file regions.

ocfs2_remove_inode_range() takes a byte range within a file and will remove
existing extents within that range. Partial clusters will be zeroed so that
any read from within the region will return zeros.

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

1 files changed, 240 insertions, 2 deletions

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index f0a6b1330a6e..11f7cf9f2511 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -541,12 +541,15 @@ int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
                           struct ocfs2_alloc_context **data_ac,
                           struct ocfs2_alloc_context **meta_ac)
 {
-        int ret, num_free_extents;
+        int ret = 0, num_free_extents;
         unsigned int max_recs_needed = clusters_to_add + 2 * extents_to_split;
         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
         *meta_ac = NULL;
-        *data_ac = NULL;
+        if (data_ac)
+                *data_ac = NULL;
+
+        BUG_ON(clusters_to_add != 0 && data_ac == NULL);
 
         mlog(0, "extend inode %llu, i_size = %lld, di->i_clusters = %u, "
              "clusters_to_add = %u, extents_to_split = %u\n",
@@ -583,6 +586,9 @@ int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
                 }
         }
 
+        if (clusters_to_add == 0)
+                goto out;
+
         ret = ocfs2_reserve_clusters(osb, clusters_to_add, data_ac);
         if (ret < 0) {
                 if (ret != -ENOSPC)
@@ -1252,6 +1258,238 @@ out:
         return ret;
 }
 
+static int __ocfs2_remove_inode_range(struct inode *inode,
+                                      struct buffer_head *di_bh,
+                                      u32 cpos, u32 phys_cpos, u32 len,
+                                      struct ocfs2_cached_dealloc_ctxt *dealloc)
+{
+        int ret;
+        u64 phys_blkno = ocfs2_clusters_to_blocks(inode->i_sb, phys_cpos);
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        struct inode *tl_inode = osb->osb_tl_inode;
+        handle_t *handle;
+        struct ocfs2_alloc_context *meta_ac = NULL;
+        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
+
+        ret = ocfs2_lock_allocators(inode, di, 0, 1, NULL, &meta_ac);
+        if (ret) {
+                mlog_errno(ret);
+                return ret;
+        }
+
+        mutex_lock(&tl_inode->i_mutex);
+
+        if (ocfs2_truncate_log_needs_flush(osb)) {
+                ret = __ocfs2_flush_truncate_log(osb);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+        }
+
+        handle = ocfs2_start_trans(osb, OCFS2_REMOVE_EXTENT_CREDITS);
+        if (handle == NULL) {
+                ret = -ENOMEM;
+                mlog_errno(ret);
+                goto out;
+        }
+
+        ret = ocfs2_journal_access(handle, inode, di_bh,
+                                   OCFS2_JOURNAL_ACCESS_WRITE);
+        if (ret) {
+                mlog_errno(ret);
+                goto out;
+        }
+
+        ret = ocfs2_remove_extent(inode, di_bh, cpos, len, handle, meta_ac,
+                                  dealloc);
+        if (ret) {
+                mlog_errno(ret);
+                goto out_commit;
+        }
+
+        OCFS2_I(inode)->ip_clusters -= len;
+        di->i_clusters = cpu_to_le32(OCFS2_I(inode)->ip_clusters);
+
+        ret = ocfs2_journal_dirty(handle, di_bh);
+        if (ret) {
+                mlog_errno(ret);
+                goto out_commit;
+        }
+
+        ret = ocfs2_truncate_log_append(osb, handle, phys_blkno, len);
+        if (ret)
+                mlog_errno(ret);
+
+out_commit:
+        ocfs2_commit_trans(osb, handle);
+out:
+        mutex_unlock(&tl_inode->i_mutex);
+
+        if (meta_ac)
+                ocfs2_free_alloc_context(meta_ac);
+
+        return ret;
+}
+
+/*
+ * Truncate a byte range, avoiding pages within partial clusters. This
+ * preserves those pages for the zeroing code to write to.
+ */
+static void ocfs2_truncate_cluster_pages(struct inode *inode, u64 byte_start,
+                                         u64 byte_len)
+{
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        loff_t start, end;
+        struct address_space *mapping = inode->i_mapping;
+
+        start = (loff_t)ocfs2_align_bytes_to_clusters(inode->i_sb, byte_start);
+        end = byte_start + byte_len;
+        end = end & ~(osb->s_clustersize - 1);
+
+        if (start < end) {
+                unmap_mapping_range(mapping, start, end - start, 0);
+                truncate_inode_pages_range(mapping, start, end - 1);
+        }
+}
+
+static int ocfs2_zero_partial_clusters(struct inode *inode,
+                                       u64 start, u64 len)
+{
+        int ret = 0;
+        u64 tmpend, end = start + len;
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        unsigned int csize = osb->s_clustersize;
+        handle_t *handle;
+
+        /*
+         * The "start" and "end" values are NOT necessarily part of
+         * the range whose allocation is being deleted. Rather, this
+         * is what the user passed in with the request. We must zero
+         * partial clusters here. There's no need to worry about
+         * physical allocation - the zeroing code knows to skip holes.
+         */
+        mlog(0, "byte start: %llu, end: %llu\n",
+             (unsigned long long)start, (unsigned long long)end);
+
+        /*
+         * If both edges are on a cluster boundary then there's no
+         * zeroing required as the region is part of the allocation to
+         * be truncated.
+         */
+        if ((start & (csize - 1)) == 0 && (end & (csize - 1)) == 0)
+                goto out;
+
+        handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
+        if (handle == NULL) {
+                ret = -ENOMEM;
+                mlog_errno(ret);
+                goto out;
+        }
+
+        /*
+         * We want to get the byte offset of the end of the 1st cluster.
+         */
+        tmpend = (u64)osb->s_clustersize + (start & ~(osb->s_clustersize - 1));
+        if (tmpend > end)
+                tmpend = end;
+
+        mlog(0, "1st range: start: %llu, tmpend: %llu\n",
+             (unsigned long long)start, (unsigned long long)tmpend);
+
+        ret = ocfs2_zero_range_for_truncate(inode, handle, start, tmpend);
+        if (ret)
+                mlog_errno(ret);
+
+        if (tmpend < end) {
+                /*
+                 * This may make start and end equal, but the zeroing
+                 * code will skip any work in that case so there's no
+                 * need to catch it up here.
+                 */
+                start = end & ~(osb->s_clustersize - 1);
+
+                mlog(0, "2nd range: start: %llu, end: %llu\n",
+                     (unsigned long long)start, (unsigned long long)end);
+
+                ret = ocfs2_zero_range_for_truncate(inode, handle, start, end);
+                if (ret)
+                        mlog_errno(ret);
+        }
+
+        ocfs2_commit_trans(osb, handle);
+out:
+        return ret;
+}
+
+static int ocfs2_remove_inode_range(struct inode *inode,
+                                    struct buffer_head *di_bh, u64 byte_start,
+                                    u64 byte_len)
+{
+        int ret = 0;
+        u32 trunc_start, trunc_len, cpos, phys_cpos, alloc_size;
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        struct ocfs2_cached_dealloc_ctxt dealloc;
+
+        ocfs2_init_dealloc_ctxt(&dealloc);
+
+        if (byte_len == 0)
+                return 0;
+
+        trunc_start = ocfs2_clusters_for_bytes(osb->sb, byte_start);
+        trunc_len = (byte_start + byte_len) >> osb->s_clustersize_bits;
+        if (trunc_len >= trunc_start)
+                trunc_len -= trunc_start;
+        else
+                trunc_len = 0;
+
+        mlog(0, "Inode: %llu, start: %llu, len: %llu, cstart: %u, clen: %u\n",
+             (unsigned long long)OCFS2_I(inode)->ip_blkno,
+             (unsigned long long)byte_start,
+             (unsigned long long)byte_len, trunc_start, trunc_len);
+
+        ret = ocfs2_zero_partial_clusters(inode, byte_start, byte_len);
+        if (ret) {
+                mlog_errno(ret);
+                goto out;
+        }
+
+        cpos = trunc_start;
+        while (trunc_len) {
+                ret = ocfs2_get_clusters(inode, cpos, &phys_cpos,
+                                         &alloc_size, NULL);
+                if (ret) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+
+                if (alloc_size > trunc_len)
+                        alloc_size = trunc_len;
+
+                /* Only do work for non-holes */
+                if (phys_cpos != 0) {
+                        ret = __ocfs2_remove_inode_range(inode, di_bh, cpos,
+                                                         phys_cpos, alloc_size,
+                                                         &dealloc);
+                        if (ret) {
+                                mlog_errno(ret);
+                                goto out;
+                        }
+                }
+
+                cpos += alloc_size;
+                trunc_len -= alloc_size;
+        }
+
+        ocfs2_truncate_cluster_pages(inode, byte_start, byte_len);
+
+out:
+        ocfs2_schedule_truncate_log_flush(osb, 1);
+        ocfs2_run_deallocs(osb, &dealloc);
+
+        return ret;
+}
+
 static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
                                          loff_t *ppos,
                                          size_t count,