ext4: fix deadlock in ext4_symlink() in ENOSPC conditions
ext4_symlink() cannot call __page_symlink() with transaction open. __page_symlink() calls ext4_write_begin() which can wait for transaction commit if we are running out of space thus causing a deadlock. Also error recovery in ext4_truncate_failed_write() does not count with the transaction being already started (although I'm not aware of any particular deadlock here). Fix the problem by stopping a transaction before calling __page_symlink() (we have to be careful and put inode to orphan list so that it gets deleted in case of crash) and starting another one after __page_symlink() returns for addition of symlink into a directory. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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7ad8e4e6ae
Коммит
df5e622340
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@ -2250,6 +2250,7 @@ static int ext4_symlink(struct inode *dir,
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handle_t *handle;
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struct inode *inode;
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int l, err, retries = 0;
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int credits;
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l = strlen(symname)+1;
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if (l > dir->i_sb->s_blocksize)
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@ -2257,10 +2258,26 @@ static int ext4_symlink(struct inode *dir,
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dquot_initialize(dir);
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if (l > EXT4_N_BLOCKS * 4) {
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/*
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* For non-fast symlinks, we just allocate inode and put it on
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* orphan list in the first transaction => we need bitmap,
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* group descriptor, sb, inode block, quota blocks.
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*/
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credits = 4 + EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);
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} else {
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/*
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* Fast symlink. We have to add entry to directory
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* (EXT4_DATA_TRANS_BLOCKS + EXT4_INDEX_EXTRA_TRANS_BLOCKS),
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* allocate new inode (bitmap, group descriptor, inode block,
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* quota blocks, sb is already counted in previous macros).
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*/
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credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
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EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
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EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);
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}
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retry:
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handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
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EXT4_INDEX_EXTRA_TRANS_BLOCKS + 5 +
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EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb));
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handle = ext4_journal_start(dir, credits);
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if (IS_ERR(handle))
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return PTR_ERR(handle);
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@ -2273,21 +2290,44 @@ retry:
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if (IS_ERR(inode))
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goto out_stop;
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if (l > sizeof(EXT4_I(inode)->i_data)) {
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if (l > EXT4_N_BLOCKS * 4) {
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inode->i_op = &ext4_symlink_inode_operations;
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ext4_set_aops(inode);
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/*
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* page_symlink() calls into ext4_prepare/commit_write.
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* We have a transaction open. All is sweetness. It also sets
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* i_size in generic_commit_write().
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* We cannot call page_symlink() with transaction started
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* because it calls into ext4_write_begin() which can wait
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* for transaction commit if we are running out of space
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* and thus we deadlock. So we have to stop transaction now
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* and restart it when symlink contents is written.
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*
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* To keep fs consistent in case of crash, we have to put inode
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* to orphan list in the mean time.
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*/
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drop_nlink(inode);
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err = ext4_orphan_add(handle, inode);
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ext4_journal_stop(handle);
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if (err)
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goto err_drop_inode;
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err = __page_symlink(inode, symname, l, 1);
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if (err)
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goto err_drop_inode;
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/*
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* Now inode is being linked into dir (EXT4_DATA_TRANS_BLOCKS
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* + EXT4_INDEX_EXTRA_TRANS_BLOCKS), inode is also modified
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*/
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handle = ext4_journal_start(dir,
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EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
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EXT4_INDEX_EXTRA_TRANS_BLOCKS + 1);
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if (IS_ERR(handle)) {
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err = PTR_ERR(handle);
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goto err_drop_inode;
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}
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inc_nlink(inode);
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err = ext4_orphan_del(handle, inode);
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if (err) {
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ext4_journal_stop(handle);
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clear_nlink(inode);
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unlock_new_inode(inode);
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ext4_mark_inode_dirty(handle, inode);
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iput(inode);
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goto out_stop;
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goto err_drop_inode;
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}
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} else {
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/* clear the extent format for fast symlink */
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@ -2303,6 +2343,10 @@ out_stop:
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if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
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goto retry;
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return err;
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err_drop_inode:
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unlock_new_inode(inode);
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iput(inode);
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return err;
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}
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static int ext4_link(struct dentry *old_dentry,
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