ext3: Fix lock inversion in ext3_symlink()
ext3_symlink() cannot call __page_symlink() with transaction open.
__page_symlink() calls ext3_write_begin() which gets page lock which ranks
above transaction start (thus lock ordering is violated) and and also
ext3_write_begin() waits for a transaction commit when we run out of space
which never happens if we hold transaction open.
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>
diff --git a/fs/ext3/namei.c b/fs/ext3/namei.c
index 32f3b86..f6ce3e7 100644
--- a/fs/ext3/namei.c
+++ b/fs/ext3/namei.c
@@ -2189,6 +2189,7 @@
handle_t *handle;
struct inode * inode;
int l, err, retries = 0;
+ int credits;
l = strlen(symname)+1;
if (l > dir->i_sb->s_blocksize)
@@ -2196,10 +2197,26 @@
dquot_initialize(dir);
+ if (l > EXT3_N_BLOCKS * 4) {
+ /*
+ * For non-fast symlinks, we just allocate inode and put it on
+ * orphan list in the first transaction => we need bitmap,
+ * group descriptor, sb, inode block, quota blocks.
+ */
+ credits = 4 + EXT3_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);
+ } else {
+ /*
+ * Fast symlink. We have to add entry to directory
+ * (EXT3_DATA_TRANS_BLOCKS + EXT3_INDEX_EXTRA_TRANS_BLOCKS),
+ * allocate new inode (bitmap, group descriptor, inode block,
+ * quota blocks, sb is already counted in previous macros).
+ */
+ credits = EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +
+ EXT3_INDEX_EXTRA_TRANS_BLOCKS + 3 +
+ EXT3_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);
+ }
retry:
- handle = ext3_journal_start(dir, EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +
- EXT3_INDEX_EXTRA_TRANS_BLOCKS + 5 +
- EXT3_MAXQUOTAS_INIT_BLOCKS(dir->i_sb));
+ handle = ext3_journal_start(dir, credits);
if (IS_ERR(handle))
return PTR_ERR(handle);
@@ -2211,21 +2228,45 @@
if (IS_ERR(inode))
goto out_stop;
- if (l > sizeof (EXT3_I(inode)->i_data)) {
+ if (l > EXT3_N_BLOCKS * 4) {
inode->i_op = &ext3_symlink_inode_operations;
ext3_set_aops(inode);
/*
- * page_symlink() calls into ext3_prepare/commit_write.
- * We have a transaction open. All is sweetness. It also sets
- * i_size in generic_commit_write().
+ * We cannot call page_symlink() with transaction started
+ * because it calls into ext3_write_begin() which acquires page
+ * lock which ranks below transaction start (and it can also
+ * wait for journal commit if we are running out of space). So
+ * we have to stop transaction now and restart it when symlink
+ * contents is written.
+ *
+ * To keep fs consistent in case of crash, we have to put inode
+ * to orphan list in the mean time.
*/
+ drop_nlink(inode);
+ err = ext3_orphan_add(handle, inode);
+ ext3_journal_stop(handle);
+ if (err)
+ goto err_drop_inode;
err = __page_symlink(inode, symname, l, 1);
+ if (err)
+ goto err_drop_inode;
+ /*
+ * Now inode is being linked into dir (EXT3_DATA_TRANS_BLOCKS
+ * + EXT3_INDEX_EXTRA_TRANS_BLOCKS), inode is also modified
+ */
+ handle = ext3_journal_start(dir,
+ EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +
+ EXT3_INDEX_EXTRA_TRANS_BLOCKS + 1);
+ if (IS_ERR(handle)) {
+ err = PTR_ERR(handle);
+ goto err_drop_inode;
+ }
+ inc_nlink(inode);
+ err = ext3_orphan_del(handle, inode);
if (err) {
+ ext3_journal_stop(handle);
drop_nlink(inode);
- unlock_new_inode(inode);
- ext3_mark_inode_dirty(handle, inode);
- iput (inode);
- goto out_stop;
+ goto err_drop_inode;
}
} else {
inode->i_op = &ext3_fast_symlink_inode_operations;
@@ -2239,6 +2280,10 @@
if (err == -ENOSPC && ext3_should_retry_alloc(dir->i_sb, &retries))
goto retry;
return err;
+err_drop_inode:
+ unlock_new_inode(inode);
+ iput (inode);
+ return err;
}
static int ext3_link (struct dentry * old_dentry,