linux/fs/btrfs/root-tree.c
Filipe Manana 72bd2323ec Btrfs: do not abort transaction at btrfs_update_root() after failure to COW path
Currently when we fail to COW a path at btrfs_update_root() we end up
always aborting the transaction. However all the current callers of
btrfs_update_root() are able to deal with errors returned from it, many do
end up aborting the transaction themselves (directly or not, such as the
transaction commit path), other BUG_ON() or just gracefully cancel whatever
they were doing.

When syncing the fsync log, we call btrfs_update_root() through
tree-log.c:update_log_root(), and if it returns an -ENOSPC error, the log
sync code does not abort the transaction, instead it gracefully handles
the error and returns -EAGAIN to the fsync handler, so that it falls back
to a transaction commit. Any other error different from -ENOSPC, makes the
log sync code abort the transaction.

So remove the transaction abort from btrfs_update_log() when we fail to
COW a path to update the root item, so that if an -ENOSPC failure happens
we avoid aborting the current transaction and have a chance of the fsync
succeeding after falling back to a transaction commit.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203413
Fixes: 79787eaab4 ("btrfs: replace many BUG_ONs with proper error handling")
Cc: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2019-05-09 11:25:27 +02:00

500 lines
13 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2007 Oracle. All rights reserved.
*/
#include <linux/err.h>
#include <linux/uuid.h>
#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "print-tree.h"
/*
* Read a root item from the tree. In case we detect a root item smaller then
* sizeof(root_item), we know it's an old version of the root structure and
* initialize all new fields to zero. The same happens if we detect mismatching
* generation numbers as then we know the root was once mounted with an older
* kernel that was not aware of the root item structure change.
*/
static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
struct btrfs_root_item *item)
{
uuid_le uuid;
u32 len;
int need_reset = 0;
len = btrfs_item_size_nr(eb, slot);
read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
min_t(u32, len, sizeof(*item)));
if (len < sizeof(*item))
need_reset = 1;
if (!need_reset && btrfs_root_generation(item)
!= btrfs_root_generation_v2(item)) {
if (btrfs_root_generation_v2(item) != 0) {
btrfs_warn(eb->fs_info,
"mismatching generation and generation_v2 found in root item. This root was probably mounted with an older kernel. Resetting all new fields.");
}
need_reset = 1;
}
if (need_reset) {
memset(&item->generation_v2, 0,
sizeof(*item) - offsetof(struct btrfs_root_item,
generation_v2));
uuid_le_gen(&uuid);
memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE);
}
}
/*
* btrfs_find_root - lookup the root by the key.
* root: the root of the root tree
* search_key: the key to search
* path: the path we search
* root_item: the root item of the tree we look for
* root_key: the root key of the tree we look for
*
* If ->offset of 'search_key' is -1ULL, it means we are not sure the offset
* of the search key, just lookup the root with the highest offset for a
* given objectid.
*
* If we find something return 0, otherwise > 0, < 0 on error.
*/
int btrfs_find_root(struct btrfs_root *root, const struct btrfs_key *search_key,
struct btrfs_path *path, struct btrfs_root_item *root_item,
struct btrfs_key *root_key)
{
struct btrfs_key found_key;
struct extent_buffer *l;
int ret;
int slot;
ret = btrfs_search_slot(NULL, root, search_key, path, 0, 0);
if (ret < 0)
return ret;
if (search_key->offset != -1ULL) { /* the search key is exact */
if (ret > 0)
goto out;
} else {
BUG_ON(ret == 0); /* Logical error */
if (path->slots[0] == 0)
goto out;
path->slots[0]--;
ret = 0;
}
l = path->nodes[0];
slot = path->slots[0];
btrfs_item_key_to_cpu(l, &found_key, slot);
if (found_key.objectid != search_key->objectid ||
found_key.type != BTRFS_ROOT_ITEM_KEY) {
ret = 1;
goto out;
}
if (root_item)
btrfs_read_root_item(l, slot, root_item);
if (root_key)
memcpy(root_key, &found_key, sizeof(found_key));
out:
btrfs_release_path(path);
return ret;
}
void btrfs_set_root_node(struct btrfs_root_item *item,
struct extent_buffer *node)
{
btrfs_set_root_bytenr(item, node->start);
btrfs_set_root_level(item, btrfs_header_level(node));
btrfs_set_root_generation(item, btrfs_header_generation(node));
}
/*
* copy the data in 'item' into the btree
*/
int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root
*root, struct btrfs_key *key, struct btrfs_root_item
*item)
{
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_path *path;
struct extent_buffer *l;
int ret;
int slot;
unsigned long ptr;
u32 old_len;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
ret = btrfs_search_slot(trans, root, key, path, 0, 1);
if (ret < 0)
goto out;
if (ret > 0) {
btrfs_crit(fs_info,
"unable to find root key (%llu %u %llu) in tree %llu",
key->objectid, key->type, key->offset,
root->root_key.objectid);
ret = -EUCLEAN;
btrfs_abort_transaction(trans, ret);
goto out;
}
l = path->nodes[0];
slot = path->slots[0];
ptr = btrfs_item_ptr_offset(l, slot);
old_len = btrfs_item_size_nr(l, slot);
/*
* If this is the first time we update the root item which originated
* from an older kernel, we need to enlarge the item size to make room
* for the added fields.
*/
if (old_len < sizeof(*item)) {
btrfs_release_path(path);
ret = btrfs_search_slot(trans, root, key, path,
-1, 1);
if (ret < 0) {
btrfs_abort_transaction(trans, ret);
goto out;
}
ret = btrfs_del_item(trans, root, path);
if (ret < 0) {
btrfs_abort_transaction(trans, ret);
goto out;
}
btrfs_release_path(path);
ret = btrfs_insert_empty_item(trans, root, path,
key, sizeof(*item));
if (ret < 0) {
btrfs_abort_transaction(trans, ret);
goto out;
}
l = path->nodes[0];
slot = path->slots[0];
ptr = btrfs_item_ptr_offset(l, slot);
}
/*
* Update generation_v2 so at the next mount we know the new root
* fields are valid.
*/
btrfs_set_root_generation_v2(item, btrfs_root_generation(item));
write_extent_buffer(l, item, ptr, sizeof(*item));
btrfs_mark_buffer_dirty(path->nodes[0]);
out:
btrfs_free_path(path);
return ret;
}
int btrfs_insert_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
const struct btrfs_key *key, struct btrfs_root_item *item)
{
/*
* Make sure generation v1 and v2 match. See update_root for details.
*/
btrfs_set_root_generation_v2(item, btrfs_root_generation(item));
return btrfs_insert_item(trans, root, key, item, sizeof(*item));
}
int btrfs_find_orphan_roots(struct btrfs_fs_info *fs_info)
{
struct btrfs_root *tree_root = fs_info->tree_root;
struct extent_buffer *leaf;
struct btrfs_path *path;
struct btrfs_key key;
struct btrfs_key root_key;
struct btrfs_root *root;
int err = 0;
int ret;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
key.objectid = BTRFS_ORPHAN_OBJECTID;
key.type = BTRFS_ORPHAN_ITEM_KEY;
key.offset = 0;
root_key.type = BTRFS_ROOT_ITEM_KEY;
root_key.offset = (u64)-1;
while (1) {
ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
if (ret < 0) {
err = ret;
break;
}
leaf = path->nodes[0];
if (path->slots[0] >= btrfs_header_nritems(leaf)) {
ret = btrfs_next_leaf(tree_root, path);
if (ret < 0)
err = ret;
if (ret != 0)
break;
leaf = path->nodes[0];
}
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
btrfs_release_path(path);
if (key.objectid != BTRFS_ORPHAN_OBJECTID ||
key.type != BTRFS_ORPHAN_ITEM_KEY)
break;
root_key.objectid = key.offset;
key.offset++;
/*
* The root might have been inserted already, as before we look
* for orphan roots, log replay might have happened, which
* triggers a transaction commit and qgroup accounting, which
* in turn reads and inserts fs roots while doing backref
* walking.
*/
root = btrfs_lookup_fs_root(fs_info, root_key.objectid);
if (root) {
WARN_ON(!test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED,
&root->state));
if (btrfs_root_refs(&root->root_item) == 0) {
set_bit(BTRFS_ROOT_DEAD_TREE, &root->state);
btrfs_add_dead_root(root);
}
continue;
}
root = btrfs_read_fs_root(tree_root, &root_key);
err = PTR_ERR_OR_ZERO(root);
if (err && err != -ENOENT) {
break;
} else if (err == -ENOENT) {
struct btrfs_trans_handle *trans;
btrfs_release_path(path);
trans = btrfs_join_transaction(tree_root);
if (IS_ERR(trans)) {
err = PTR_ERR(trans);
btrfs_handle_fs_error(fs_info, err,
"Failed to start trans to delete orphan item");
break;
}
err = btrfs_del_orphan_item(trans, tree_root,
root_key.objectid);
btrfs_end_transaction(trans);
if (err) {
btrfs_handle_fs_error(fs_info, err,
"Failed to delete root orphan item");
break;
}
continue;
}
err = btrfs_init_fs_root(root);
if (err) {
btrfs_free_fs_root(root);
break;
}
set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);
err = btrfs_insert_fs_root(fs_info, root);
if (err) {
BUG_ON(err == -EEXIST);
btrfs_free_fs_root(root);
break;
}
if (btrfs_root_refs(&root->root_item) == 0) {
set_bit(BTRFS_ROOT_DEAD_TREE, &root->state);
btrfs_add_dead_root(root);
}
}
btrfs_free_path(path);
return err;
}
/* drop the root item for 'key' from the tree root */
int btrfs_del_root(struct btrfs_trans_handle *trans,
const struct btrfs_key *key)
{
struct btrfs_root *root = trans->fs_info->tree_root;
struct btrfs_path *path;
int ret;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
ret = btrfs_search_slot(trans, root, key, path, -1, 1);
if (ret < 0)
goto out;
BUG_ON(ret != 0);
ret = btrfs_del_item(trans, root, path);
out:
btrfs_free_path(path);
return ret;
}
int btrfs_del_root_ref(struct btrfs_trans_handle *trans, u64 root_id,
u64 ref_id, u64 dirid, u64 *sequence, const char *name,
int name_len)
{
struct btrfs_root *tree_root = trans->fs_info->tree_root;
struct btrfs_path *path;
struct btrfs_root_ref *ref;
struct extent_buffer *leaf;
struct btrfs_key key;
unsigned long ptr;
int err = 0;
int ret;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
key.objectid = root_id;
key.type = BTRFS_ROOT_BACKREF_KEY;
key.offset = ref_id;
again:
ret = btrfs_search_slot(trans, tree_root, &key, path, -1, 1);
BUG_ON(ret < 0);
if (ret == 0) {
leaf = path->nodes[0];
ref = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_root_ref);
WARN_ON(btrfs_root_ref_dirid(leaf, ref) != dirid);
WARN_ON(btrfs_root_ref_name_len(leaf, ref) != name_len);
ptr = (unsigned long)(ref + 1);
WARN_ON(memcmp_extent_buffer(leaf, name, ptr, name_len));
*sequence = btrfs_root_ref_sequence(leaf, ref);
ret = btrfs_del_item(trans, tree_root, path);
if (ret) {
err = ret;
goto out;
}
} else
err = -ENOENT;
if (key.type == BTRFS_ROOT_BACKREF_KEY) {
btrfs_release_path(path);
key.objectid = ref_id;
key.type = BTRFS_ROOT_REF_KEY;
key.offset = root_id;
goto again;
}
out:
btrfs_free_path(path);
return err;
}
/*
* add a btrfs_root_ref item. type is either BTRFS_ROOT_REF_KEY
* or BTRFS_ROOT_BACKREF_KEY.
*
* The dirid, sequence, name and name_len refer to the directory entry
* that is referencing the root.
*
* For a forward ref, the root_id is the id of the tree referencing
* the root and ref_id is the id of the subvol or snapshot.
*
* For a back ref the root_id is the id of the subvol or snapshot and
* ref_id is the id of the tree referencing it.
*
* Will return 0, -ENOMEM, or anything from the CoW path
*/
int btrfs_add_root_ref(struct btrfs_trans_handle *trans, u64 root_id,
u64 ref_id, u64 dirid, u64 sequence, const char *name,
int name_len)
{
struct btrfs_root *tree_root = trans->fs_info->tree_root;
struct btrfs_key key;
int ret;
struct btrfs_path *path;
struct btrfs_root_ref *ref;
struct extent_buffer *leaf;
unsigned long ptr;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
key.objectid = root_id;
key.type = BTRFS_ROOT_BACKREF_KEY;
key.offset = ref_id;
again:
ret = btrfs_insert_empty_item(trans, tree_root, path, &key,
sizeof(*ref) + name_len);
if (ret) {
btrfs_abort_transaction(trans, ret);
btrfs_free_path(path);
return ret;
}
leaf = path->nodes[0];
ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
btrfs_set_root_ref_dirid(leaf, ref, dirid);
btrfs_set_root_ref_sequence(leaf, ref, sequence);
btrfs_set_root_ref_name_len(leaf, ref, name_len);
ptr = (unsigned long)(ref + 1);
write_extent_buffer(leaf, name, ptr, name_len);
btrfs_mark_buffer_dirty(leaf);
if (key.type == BTRFS_ROOT_BACKREF_KEY) {
btrfs_release_path(path);
key.objectid = ref_id;
key.type = BTRFS_ROOT_REF_KEY;
key.offset = root_id;
goto again;
}
btrfs_free_path(path);
return 0;
}
/*
* Old btrfs forgets to init root_item->flags and root_item->byte_limit
* for subvolumes. To work around this problem, we steal a bit from
* root_item->inode_item->flags, and use it to indicate if those fields
* have been properly initialized.
*/
void btrfs_check_and_init_root_item(struct btrfs_root_item *root_item)
{
u64 inode_flags = btrfs_stack_inode_flags(&root_item->inode);
if (!(inode_flags & BTRFS_INODE_ROOT_ITEM_INIT)) {
inode_flags |= BTRFS_INODE_ROOT_ITEM_INIT;
btrfs_set_stack_inode_flags(&root_item->inode, inode_flags);
btrfs_set_root_flags(root_item, 0);
btrfs_set_root_limit(root_item, 0);
}
}
void btrfs_update_root_times(struct btrfs_trans_handle *trans,
struct btrfs_root *root)
{
struct btrfs_root_item *item = &root->root_item;
struct timespec64 ct;
ktime_get_real_ts64(&ct);
spin_lock(&root->root_item_lock);
btrfs_set_root_ctransid(item, trans->transid);
btrfs_set_stack_timespec_sec(&item->ctime, ct.tv_sec);
btrfs_set_stack_timespec_nsec(&item->ctime, ct.tv_nsec);
spin_unlock(&root->root_item_lock);
}