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ocfs2: btree support for removal of arbirtrary extents
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Add code to the btree paths to support the removal of arbitrary regions
within an existing extent. With proper higher level support this can be used
to "punch holes" in a file. Truncate (a special case of hole punching) could
also be converted to use these methods.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
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Mark Fasheh committed Jul 11, 2007
1 parent 2ae99a6 commit d0c7d70
Showing 1 changed file with 367 additions and 0 deletions.
367 changes: 367 additions & 0 deletions fs/ocfs2/alloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4139,6 +4139,373 @@ int ocfs2_mark_extent_written(struct inode *inode, struct buffer_head *di_bh,
return ret;
}

static int ocfs2_split_tree(struct inode *inode, struct buffer_head *di_bh,
handle_t *handle, struct ocfs2_path *path,
int index, u32 new_range,
struct ocfs2_alloc_context *meta_ac)
{
int ret, depth, credits = handle->h_buffer_credits;
struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
struct buffer_head *last_eb_bh = NULL;
struct ocfs2_extent_block *eb;
struct ocfs2_extent_list *rightmost_el, *el;
struct ocfs2_extent_rec split_rec;
struct ocfs2_extent_rec *rec;
struct ocfs2_insert_type insert;

/*
* Setup the record to split before we grow the tree.
*/
el = path_leaf_el(path);
rec = &el->l_recs[index];
ocfs2_make_right_split_rec(inode->i_sb, &split_rec, new_range, rec);

depth = path->p_tree_depth;
if (depth > 0) {
ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
le64_to_cpu(di->i_last_eb_blk),
&last_eb_bh, OCFS2_BH_CACHED, inode);
if (ret < 0) {
mlog_errno(ret);
goto out;
}

eb = (struct ocfs2_extent_block *) last_eb_bh->b_data;
rightmost_el = &eb->h_list;
} else
rightmost_el = path_leaf_el(path);

credits += path->p_tree_depth + ocfs2_extend_meta_needed(di);
ret = ocfs2_extend_trans(handle, credits);
if (ret) {
mlog_errno(ret);
goto out;
}

if (le16_to_cpu(rightmost_el->l_next_free_rec) ==
le16_to_cpu(rightmost_el->l_count)) {
int old_depth = depth;

ret = ocfs2_grow_tree(inode, handle, di_bh, &depth, &last_eb_bh,
meta_ac);
if (ret) {
mlog_errno(ret);
goto out;
}

if (old_depth != depth) {
eb = (struct ocfs2_extent_block *)last_eb_bh->b_data;
rightmost_el = &eb->h_list;
}
}

memset(&insert, 0, sizeof(struct ocfs2_insert_type));
insert.ins_appending = APPEND_NONE;
insert.ins_contig = CONTIG_NONE;
insert.ins_split = SPLIT_RIGHT;
insert.ins_free_records = le16_to_cpu(rightmost_el->l_count)
- le16_to_cpu(rightmost_el->l_next_free_rec);
insert.ins_tree_depth = depth;

ret = ocfs2_do_insert_extent(inode, handle, di_bh, &split_rec, &insert);
if (ret)
mlog_errno(ret);

out:
brelse(last_eb_bh);
return ret;
}

static int ocfs2_truncate_rec(struct inode *inode, handle_t *handle,
struct ocfs2_path *path, int index,
struct ocfs2_cached_dealloc_ctxt *dealloc,
u32 cpos, u32 len)
{
int ret;
u32 left_cpos, rec_range, trunc_range;
int wants_rotate = 0, is_rightmost_tree_rec = 0;
struct super_block *sb = inode->i_sb;
struct ocfs2_path *left_path = NULL;
struct ocfs2_extent_list *el = path_leaf_el(path);
struct ocfs2_extent_rec *rec;
struct ocfs2_extent_block *eb;

if (ocfs2_is_empty_extent(&el->l_recs[0]) && index > 0) {
ret = ocfs2_rotate_tree_left(inode, handle, path, dealloc);
if (ret) {
mlog_errno(ret);
goto out;
}

index--;
}

if (index == (le16_to_cpu(el->l_next_free_rec) - 1) &&
path->p_tree_depth) {
/*
* Check whether this is the rightmost tree record. If
* we remove all of this record or part of its right
* edge then an update of the record lengths above it
* will be required.
*/
eb = (struct ocfs2_extent_block *)path_leaf_bh(path)->b_data;
if (eb->h_next_leaf_blk == 0)
is_rightmost_tree_rec = 1;
}

rec = &el->l_recs[index];
if (index == 0 && path->p_tree_depth &&
le32_to_cpu(rec->e_cpos) == cpos) {
/*
* Changing the leftmost offset (via partial or whole
* record truncate) of an interior (or rightmost) path
* means we have to update the subtree that is formed
* by this leaf and the one to it's left.
*
* There are two cases we can skip:
* 1) Path is the leftmost one in our inode tree.
* 2) The leaf is rightmost and will be empty after
* we remove the extent record - the rotate code
* knows how to update the newly formed edge.
*/

ret = ocfs2_find_cpos_for_left_leaf(inode->i_sb, path,
&left_cpos);
if (ret) {
mlog_errno(ret);
goto out;
}

if (left_cpos && le16_to_cpu(el->l_next_free_rec) > 1) {
left_path = ocfs2_new_path(path_root_bh(path),
path_root_el(path));
if (!left_path) {
ret = -ENOMEM;
mlog_errno(ret);
goto out;
}

ret = ocfs2_find_path(inode, left_path, left_cpos);
if (ret) {
mlog_errno(ret);
goto out;
}
}
}

ret = ocfs2_extend_rotate_transaction(handle, 0,
handle->h_buffer_credits,
path);
if (ret) {
mlog_errno(ret);
goto out;
}

ret = ocfs2_journal_access_path(inode, handle, path);
if (ret) {
mlog_errno(ret);
goto out;
}

ret = ocfs2_journal_access_path(inode, handle, left_path);
if (ret) {
mlog_errno(ret);
goto out;
}

rec_range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
trunc_range = cpos + len;

if (le32_to_cpu(rec->e_cpos) == cpos && rec_range == trunc_range) {
int next_free;

memset(rec, 0, sizeof(*rec));
ocfs2_cleanup_merge(el, index);
wants_rotate = 1;

next_free = le16_to_cpu(el->l_next_free_rec);
if (is_rightmost_tree_rec && next_free > 1) {
/*
* We skip the edge update if this path will
* be deleted by the rotate code.
*/
rec = &el->l_recs[next_free - 1];
ocfs2_adjust_rightmost_records(inode, handle, path,
rec);
}
} else if (le32_to_cpu(rec->e_cpos) == cpos) {
/* Remove leftmost portion of the record. */
le32_add_cpu(&rec->e_cpos, len);
le64_add_cpu(&rec->e_blkno, ocfs2_clusters_to_blocks(sb, len));
le16_add_cpu(&rec->e_leaf_clusters, -len);
} else if (rec_range == trunc_range) {
/* Remove rightmost portion of the record */
le16_add_cpu(&rec->e_leaf_clusters, -len);
if (is_rightmost_tree_rec)
ocfs2_adjust_rightmost_records(inode, handle, path, rec);
} else {
/* Caller should have trapped this. */
mlog(ML_ERROR, "Inode %llu: Invalid record truncate: (%u, %u) "
"(%u, %u)\n", (unsigned long long)OCFS2_I(inode)->ip_blkno,
le32_to_cpu(rec->e_cpos),
le16_to_cpu(rec->e_leaf_clusters), cpos, len);
BUG();
}

if (left_path) {
int subtree_index;

subtree_index = ocfs2_find_subtree_root(inode, left_path, path);
ocfs2_complete_edge_insert(inode, handle, left_path, path,
subtree_index);
}

ocfs2_journal_dirty(handle, path_leaf_bh(path));

ret = ocfs2_rotate_tree_left(inode, handle, path, dealloc);
if (ret) {
mlog_errno(ret);
goto out;
}

out:
ocfs2_free_path(left_path);
return ret;
}

static int ocfs2_remove_extent(struct inode *inode, struct buffer_head *di_bh,
u32 cpos, u32 len, handle_t *handle,
struct ocfs2_alloc_context *meta_ac,
struct ocfs2_cached_dealloc_ctxt *dealloc)
{
int ret, index;
u32 rec_range, trunc_range;
struct ocfs2_extent_rec *rec;
struct ocfs2_extent_list *el;
struct ocfs2_path *path;

ocfs2_extent_map_trunc(inode, 0);

path = ocfs2_new_inode_path(di_bh);
if (!path) {
ret = -ENOMEM;
mlog_errno(ret);
goto out;
}

ret = ocfs2_find_path(inode, path, cpos);
if (ret) {
mlog_errno(ret);
goto out;
}

el = path_leaf_el(path);
index = ocfs2_search_extent_list(el, cpos);
if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
ocfs2_error(inode->i_sb,
"Inode %llu has an extent at cpos %u which can no "
"longer be found.\n",
(unsigned long long)OCFS2_I(inode)->ip_blkno, cpos);
ret = -EROFS;
goto out;
}

/*
* We have 3 cases of extent removal:
* 1) Range covers the entire extent rec
* 2) Range begins or ends on one edge of the extent rec
* 3) Range is in the middle of the extent rec (no shared edges)
*
* For case 1 we remove the extent rec and left rotate to
* fill the hole.
*
* For case 2 we just shrink the existing extent rec, with a
* tree update if the shrinking edge is also the edge of an
* extent block.
*
* For case 3 we do a right split to turn the extent rec into
* something case 2 can handle.
*/
rec = &el->l_recs[index];
rec_range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
trunc_range = cpos + len;

BUG_ON(cpos < le32_to_cpu(rec->e_cpos) || trunc_range > rec_range);

mlog(0, "Inode %llu, remove (cpos %u, len %u). Existing index %d "
"(cpos %u, len %u)\n",
(unsigned long long)OCFS2_I(inode)->ip_blkno, cpos, len, index,
le32_to_cpu(rec->e_cpos), ocfs2_rec_clusters(el, rec));

if (le32_to_cpu(rec->e_cpos) == cpos || rec_range == trunc_range) {
ret = ocfs2_truncate_rec(inode, handle, path, index, dealloc,
cpos, len);
if (ret) {
mlog_errno(ret);
goto out;
}
} else {
ret = ocfs2_split_tree(inode, di_bh, handle, path, index,
trunc_range, meta_ac);
if (ret) {
mlog_errno(ret);
goto out;
}

/*
* The split could have manipulated the tree enough to
* move the record location, so we have to look for it again.
*/
ocfs2_reinit_path(path, 1);

ret = ocfs2_find_path(inode, path, cpos);
if (ret) {
mlog_errno(ret);
goto out;
}

el = path_leaf_el(path);
index = ocfs2_search_extent_list(el, cpos);
if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
ocfs2_error(inode->i_sb,
"Inode %llu: split at cpos %u lost record.",
(unsigned long long)OCFS2_I(inode)->ip_blkno,
cpos);
ret = -EROFS;
goto out;
}

/*
* Double check our values here. If anything is fishy,
* it's easier to catch it at the top level.
*/
rec = &el->l_recs[index];
rec_range = le32_to_cpu(rec->e_cpos) +
ocfs2_rec_clusters(el, rec);
if (rec_range != trunc_range) {
ocfs2_error(inode->i_sb,
"Inode %llu: error after split at cpos %u"
"trunc len %u, existing record is (%u,%u)",
(unsigned long long)OCFS2_I(inode)->ip_blkno,
cpos, len, le32_to_cpu(rec->e_cpos),
ocfs2_rec_clusters(el, rec));
ret = -EROFS;
goto out;
}

ret = ocfs2_truncate_rec(inode, handle, path, index, dealloc,
cpos, len);
if (ret) {
mlog_errno(ret);
goto out;
}
}

out:
ocfs2_free_path(path);
return ret;
}

static inline int ocfs2_truncate_log_needs_flush(struct ocfs2_super *osb)
{
struct buffer_head *tl_bh = osb->osb_tl_bh;
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