[Ocfs2-devel] [PATCH] ocfs2: try to reuse extent block in dealloc without meta_alloc
Changwei Ge
ge.changwei at h3c.com
Mon Dec 25 22:22:48 PST 2017
A crash issue was reported by John.
The call trace follows:
ocfs2_split_extent+0x1ad3/0x1b40 [ocfs2]
ocfs2_change_extent_flag+0x33a/0x470 [ocfs2]
ocfs2_mark_extent_written+0x172/0x220 [ocfs2]
ocfs2_dio_end_io+0x62d/0x910 [ocfs2]
dio_complete+0x19a/0x1a0
do_blockdev_direct_IO+0x19dd/0x1eb0
__blockdev_direct_IO+0x43/0x50
ocfs2_direct_IO+0x8f/0xa0 [ocfs2]
generic_file_direct_write+0xb2/0x170
__generic_file_write_iter+0xc3/0x1b0
ocfs2_file_write_iter+0x4bb/0xca0 [ocfs2]
__vfs_write+0xae/0xf0
vfs_write+0xb8/0x1b0
SyS_write+0x4f/0xb0
system_call_fastpath+0x16/0x75
The BUG code told that extent tree wants to grow but no metadata
was reserved ahead of time.
From my investigation into this issue, the root cause it that although
enough metadata is not reserved, there should be enough for following use.
Rightmost extent is merged into its left one due to a certain times of
marking extent written. Because during marking extent written, we got many
physically continuous extents. At last, an empty extent showed up and the
rightmost path is removed from extent tree.
Add a new mechanism to reuse extent block cached in dealloc which were
just unlinked from extent tree to solve this crash issue.
Criteria is that during marking extents *written*, if extent rotation
and merging results in unlinking extent with growing extent tree later
without any metadata reserved ahead of time, try to reuse those extents
in dealloc in which deleted extents are cached.
Also, this patch addresses the issue John reported that ::dw_zero_count is
not calculated properly.
After applying this patch, the issue John reported was gone.
Thanks for the reproducer provided by John.
And this patch has passed ocfs2-test(29 cases) suite running by New H3C Group.
Reported-by: John Lightsey <john at nixnuts.net>
Signed-off-by: Changwei Ge <ge.changwei at h3c.com>
---
fs/ocfs2/alloc.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
fs/ocfs2/alloc.h | 1 +
fs/ocfs2/aops.c | 14 ++++--
3 files changed, 135 insertions(+), 8 deletions(-)
diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index ab5105f..eb41074 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -165,6 +165,13 @@ static int ocfs2_dinode_insert_check(struct ocfs2_extent_tree *et,
struct ocfs2_extent_rec *rec);
static int ocfs2_dinode_sanity_check(struct ocfs2_extent_tree *et);
static void ocfs2_dinode_fill_root_el(struct ocfs2_extent_tree *et);
+
+static int ocfs2_reuse_blk_from_dealloc(handle_t *handle,
+ struct ocfs2_extent_tree *et,
+ struct buffer_head **new_eb_bh,
+ int blk_cnt);
+static int ocfs2_is_dealloc_empty(struct ocfs2_extent_tree *et);
+
static const struct ocfs2_extent_tree_operations ocfs2_dinode_et_ops = {
.eo_set_last_eb_blk = ocfs2_dinode_set_last_eb_blk,
.eo_get_last_eb_blk = ocfs2_dinode_get_last_eb_blk,
@@ -448,6 +455,7 @@ static void __ocfs2_init_extent_tree(struct ocfs2_extent_tree *et,
if (!obj)
obj = (void *)bh->b_data;
et->et_object = obj;
+ et->et_dealloc = NULL;
et->et_ops->eo_fill_root_el(et);
if (!et->et_ops->eo_fill_max_leaf_clusters)
@@ -1213,8 +1221,15 @@ static int ocfs2_add_branch(handle_t *handle,
goto bail;
}
- status = ocfs2_create_new_meta_bhs(handle, et, new_blocks,
- meta_ac, new_eb_bhs);
+ if (meta_ac) {
+ status = ocfs2_create_new_meta_bhs(handle, et, new_blocks,
+ meta_ac, new_eb_bhs);
+ } else if (!ocfs2_is_dealloc_empty(et)) {
+ status = ocfs2_reuse_blk_from_dealloc(handle, et,
+ new_eb_bhs, new_blocks);
+ } else {
+ BUG();
+ }
if (status < 0) {
mlog_errno(status);
goto bail;
@@ -1347,8 +1362,15 @@ static int ocfs2_shift_tree_depth(handle_t *handle,
struct ocfs2_extent_list *root_el;
struct ocfs2_extent_list *eb_el;
- status = ocfs2_create_new_meta_bhs(handle, et, 1, meta_ac,
- &new_eb_bh);
+ if (meta_ac) {
+ status = ocfs2_create_new_meta_bhs(handle, et, 1, meta_ac,
+ &new_eb_bh);
+ } else if (!ocfs2_is_dealloc_empty(et)) {
+ status = ocfs2_reuse_blk_from_dealloc(handle, et,
+ &new_eb_bh, 1);
+ } else {
+ BUG();
+ }
if (status < 0) {
mlog_errno(status);
goto bail;
@@ -1511,7 +1533,7 @@ static int ocfs2_grow_tree(handle_t *handle, struct ocfs2_extent_tree *et,
int depth = le16_to_cpu(el->l_tree_depth);
struct buffer_head *bh = NULL;
- BUG_ON(meta_ac == NULL);
+ BUG_ON(meta_ac == NULL && ocfs2_is_dealloc_empty(et));
shift = ocfs2_find_branch_target(et, &bh);
if (shift < 0) {
@@ -6585,6 +6607,102 @@ ocfs2_find_per_slot_free_list(int type,
return fl;
}
+/* Return Value 1 indicates empty */
+static int ocfs2_is_dealloc_empty(struct ocfs2_extent_tree *et)
+{
+ struct ocfs2_per_slot_free_list *fl;
+ struct ocfs2_super *osb =
+ OCFS2_SB(ocfs2_metadata_cache_get_super(et->et_ci));
+
+ if (!et->et_dealloc)
+ return 1;
+
+ fl = ocfs2_find_per_slot_free_list(EXTENT_ALLOC_SYSTEM_INODE,
+ osb->slot_num, et->et_dealloc);
+
+ return fl ? 0 : 1;
+}
+
+/* If extent was deleted from tree due to extent rotation and merging, and
+ * no metadata is reserved ahead of time. Try to reuse some extents
+ * just deleted. This is only used to reuse extent blocks.
+ * It is supposed to find enough extent blocks in dealloc if our estimation
+ * on metadata is accurate.
+ */
+static int ocfs2_reuse_blk_from_dealloc(handle_t *handle,
+ struct ocfs2_extent_tree *et,
+ struct buffer_head **new_eb_bh,
+ int blk_cnt)
+{
+ int i, status = -ENOSPC;
+ struct ocfs2_cached_dealloc_ctxt *dealloc;
+ struct ocfs2_per_slot_free_list *fl;
+ struct ocfs2_cached_block_free *bf;
+ struct ocfs2_extent_block *eb;
+ struct ocfs2_super *osb =
+ OCFS2_SB(ocfs2_metadata_cache_get_super(et->et_ci));
+
+ dealloc = et->et_dealloc;
+ if (!dealloc)
+ goto bail;
+
+ for (i = 0; i < blk_cnt; i++) {
+ fl = ocfs2_find_per_slot_free_list(EXTENT_ALLOC_SYSTEM_INODE,
+ osb->slot_num, dealloc);
+ /* The caller should guarantee that dealloc has cached some
+ * extent blocks.
+ */
+ BUG_ON(!fl);
+
+ dealloc->c_first_suballocator = fl->f_next_suballocator;
+ bf = fl->f_first;
+ new_eb_bh[i] = sb_getblk(osb->sb, bf->free_blk);
+ if (new_eb_bh[i] == NULL) {
+ status = -ENOMEM;
+ mlog_errno(status);
+ goto bail;
+ }
+
+ mlog(0, "Reusing block(%llu) from dealloc\n", bf->free_blk);
+
+ ocfs2_set_new_buffer_uptodate(et->et_ci, new_eb_bh[i]);
+
+ status = ocfs2_journal_access_eb(handle, et->et_ci,
+ new_eb_bh[i],
+ OCFS2_JOURNAL_ACCESS_CREATE);
+ if (status < 0) {
+ mlog_errno(status);
+ goto bail;
+ }
+
+ memset(new_eb_bh[i]->b_data, 0, osb->sb->s_blocksize);
+ eb = (struct ocfs2_extent_block *) new_eb_bh[i]->b_data;
+
+ /* We can't guarantee that buffer head is still cached, so
+ * polutlate the extent block again.
+ */
+ strcpy(eb->h_signature, OCFS2_EXTENT_BLOCK_SIGNATURE);
+ eb->h_blkno = cpu_to_le64(bf->free_blk);
+ eb->h_fs_generation = cpu_to_le32(osb->fs_generation);
+ eb->h_suballoc_slot = cpu_to_le16(osb->slot_num);
+ eb->h_suballoc_loc = cpu_to_le64(bf->free_bg);
+ eb->h_suballoc_bit = cpu_to_le16(bf->free_bit);
+ eb->h_list.l_count =
+ cpu_to_le16(ocfs2_extent_recs_per_eb(osb->sb));
+
+ /* We'll also be dirtied by the caller, so
+ * this isn't absolutely necessary.
+ */
+ ocfs2_journal_dirty(handle, new_eb_bh[i]);
+
+ kfree(fl);
+ kfree(bf);
+ }
+
+bail:
+ return status;
+}
+
int ocfs2_cache_block_dealloc(struct ocfs2_cached_dealloc_ctxt *ctxt,
int type, int slot, u64 suballoc,
u64 blkno, unsigned int bit)
diff --git a/fs/ocfs2/alloc.h b/fs/ocfs2/alloc.h
index 27b75cf..250bcac 100644
--- a/fs/ocfs2/alloc.h
+++ b/fs/ocfs2/alloc.h
@@ -61,6 +61,7 @@ struct ocfs2_extent_tree {
ocfs2_journal_access_func et_root_journal_access;
void *et_object;
unsigned int et_max_leaf_clusters;
+ struct ocfs2_cached_dealloc_ctxt *et_dealloc;
};
/*
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index d151632..1bbd5c8 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -797,6 +797,7 @@ struct ocfs2_write_ctxt {
struct ocfs2_cached_dealloc_ctxt w_dealloc;
struct list_head w_unwritten_list;
+ unsigned int w_unwritten_count;
};
void ocfs2_unlock_and_free_pages(struct page **pages, int num_pages)
@@ -1386,6 +1387,7 @@ static int ocfs2_unwritten_check(struct inode *inode,
desc->c_clear_unwritten = 0;
list_add_tail(&new->ue_ip_node, &oi->ip_unwritten_list);
list_add_tail(&new->ue_node, &wc->w_unwritten_list);
+ wc->w_unwritten_count++;
new = NULL;
unlock:
spin_unlock(&oi->ip_lock);
@@ -1762,8 +1764,8 @@ int ocfs2_write_begin_nolock(struct address_space *mapping,
*/
ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode),
wc->w_di_bh);
- ret = ocfs2_lock_allocators(inode, &et,
- clusters_to_alloc, extents_to_split,
+ ret = ocfs2_lock_allocators(inode, &et, clusters_to_alloc,
+ 2*extents_to_split,
&data_ac, &meta_ac);
if (ret) {
mlog_errno(ret);
@@ -2256,7 +2258,7 @@ static int ocfs2_dio_wr_get_block(struct inode *inode, sector_t iblock,
ue->ue_phys = desc->c_phys;
list_splice_tail_init(&wc->w_unwritten_list, &dwc->dw_zero_list);
- dwc->dw_zero_count++;
+ dwc->dw_zero_count += wc->w_unwritten_count;
}
ret = ocfs2_write_end_nolock(inode->i_mapping, pos, len, len, wc);
@@ -2330,6 +2332,12 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);
+ /* Attach dealloc with extent tree in case that we may reuse extents
+ * which are already unlinked from current extent tree due to extent
+ * rotation and merging.
+ */
+ et.et_dealloc = &dealloc;
+
ret = ocfs2_lock_allocators(inode, &et, 0, dwc->dw_zero_count*2,
&data_ac, &meta_ac);
if (ret) {
--
2.7.4
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