mutex_unlock(&inode->i_mutex);
/*
- * we want to make sure fsync finds this change
- * but we haven't joined a transaction running right now.
- *
- * Later on, someone is sure to update the inode and get the
- * real transid recorded.
- *
- * We set last_trans now to the fs_info generation + 1,
- * this will either be one more than the running transaction
- * or the generation used for the next transaction if there isn't
- * one running right now.
- *
* We also have to set last_sub_trans to the current log transid,
* otherwise subsequent syncs to a file that's been synced in this
* transaction will appear to have already occured.
*/
- BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;
BTRFS_I(inode)->last_sub_trans = root->log_transid;
if (num_written > 0) {
err = generic_write_sync(file, pos, num_written);
atomic_inc(&root->log_batch);
/*
- * check the transaction that last modified this inode
- * and see if its already been committed
- */
- if (!BTRFS_I(inode)->last_trans) {
- mutex_unlock(&inode->i_mutex);
- goto out;
- }
-
- /*
- * if the last transaction that changed this file was before
- * the current transaction, we can bail out now without any
- * syncing
+ * If the last transaction that changed this file was before the current
+ * transaction and we have the full sync flag set in our inode, we can
+ * bail out now without any syncing.
+ *
+ * Note that we can't bail out if the full sync flag isn't set. This is
+ * because when the full sync flag is set we start all ordered extents
+ * and wait for them to fully complete - when they complete they update
+ * the inode's last_trans field through:
+ *
+ * btrfs_finish_ordered_io() ->
+ * btrfs_update_inode_fallback() ->
+ * btrfs_update_inode() ->
+ * btrfs_set_inode_last_trans()
+ *
+ * So we are sure that last_trans is up to date and can do this check to
+ * bail out safely. For the fast path, when the full sync flag is not
+ * set in our inode, we can not do it because we start only our ordered
+ * extents and don't wait for them to complete (that is when
+ * btrfs_finish_ordered_io runs), so here at this point their last_trans
+ * value might be less than or equals to fs_info->last_trans_committed,
+ * and setting a speculative last_trans for an inode when a buffered
+ * write is made (such as fs_info->generation + 1 for example) would not
+ * be reliable since after setting the value and before fsync is called
+ * any number of transactions can start and commit (transaction kthread
+ * commits the current transaction periodically), and a transaction
+ * commit does not start nor waits for ordered extents to complete.
*/
smp_mb();
if (btrfs_inode_in_log(inode, root->fs_info->generation) ||
- BTRFS_I(inode)->last_trans <=
- root->fs_info->last_trans_committed) {
- BTRFS_I(inode)->last_trans = 0;
-
+ (full_sync && BTRFS_I(inode)->last_trans <=
+ root->fs_info->last_trans_committed)) {
/*
* We'v had everything committed since the last time we were
* modified so clear this flag in case it was set for whatever
bool same_page;
bool no_holes = btrfs_fs_incompat(root->fs_info, NO_HOLES);
u64 ino_size;
+ bool truncated_page = false;
+ bool updated_inode = false;
ret = btrfs_wait_ordered_range(inode, offset, len);
if (ret)
* entire page.
*/
if (same_page && len < PAGE_CACHE_SIZE) {
- if (offset < ino_size)
+ if (offset < ino_size) {
+ truncated_page = true;
ret = btrfs_truncate_page(inode, offset, len, 0);
+ } else {
+ ret = 0;
+ }
goto out_only_mutex;
}
/* zero back part of the first page */
if (offset < ino_size) {
+ truncated_page = true;
ret = btrfs_truncate_page(inode, offset, 0, 0);
if (ret) {
mutex_unlock(&inode->i_mutex);
if (!ret) {
/* zero the front end of the last page */
if (tail_start + tail_len < ino_size) {
+ truncated_page = true;
ret = btrfs_truncate_page(inode,
tail_start + tail_len, 0, 1);
if (ret)
}
if (lockend < lockstart) {
- mutex_unlock(&inode->i_mutex);
- return 0;
+ ret = 0;
+ goto out_only_mutex;
}
while (1) {
trans->block_rsv = &root->fs_info->trans_block_rsv;
ret = btrfs_update_inode(trans, root, inode);
+ updated_inode = true;
btrfs_end_transaction(trans, root);
btrfs_btree_balance_dirty(root);
out_free:
unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
&cached_state, GFP_NOFS);
out_only_mutex:
+ if (!updated_inode && truncated_page && !ret && !err) {
+ /*
+ * If we only end up zeroing part of a page, we still need to
+ * update the inode item, so that all the time fields are
+ * updated as well as the necessary btrfs inode in memory fields
+ * for detecting, at fsync time, if the inode isn't yet in the
+ * log tree or it's there but not up to date.
+ */
+ trans = btrfs_start_transaction(root, 1);
+ if (IS_ERR(trans)) {
+ err = PTR_ERR(trans);
+ } else {
+ err = btrfs_update_inode(trans, root, inode);
+ ret = btrfs_end_transaction(trans, root);
+ }
+ }
mutex_unlock(&inode->i_mutex);
if (ret && !err)
err = ret;
git.openpandora.org / pandora-kernel.git / blobdiff