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authorJan Kara <jack@suse.cz>2011-05-03 11:12:58 -0400
committerTheodore Ts'o <tytso@mit.edu>2011-05-03 11:12:58 -0400
commitdf5e6223407e3e645065c4bd968fee007f0e0287 (patch)
treed5027dc9645dea4a5536819ac98f4299757fff22 /fs/ext4/namei.c
parent7ad8e4e6ae2a7c95445ee1715b1714106fb95037 (diff)
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>
Diffstat (limited to 'fs/ext4/namei.c')
-rw-r--r--fs/ext4/namei.c66
1 files changed, 55 insertions, 11 deletions
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index cadf04b924aa..3c7a06e58469 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2250,6 +2250,7 @@ static int ext4_symlink(struct inode *dir,
handle_t *handle;
struct inode *inode;
int l, err, retries = 0;
+ int credits;
l = strlen(symname)+1;
if (l > dir->i_sb->s_blocksize)
@@ -2257,10 +2258,26 @@ static int ext4_symlink(struct inode *dir,
dquot_initialize(dir);
+ if (l > EXT4_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 + EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);
+ } else {
+ /*
+ * Fast symlink. We have to add entry to directory
+ * (EXT4_DATA_TRANS_BLOCKS + EXT4_INDEX_EXTRA_TRANS_BLOCKS),
+ * allocate new inode (bitmap, group descriptor, inode block,
+ * quota blocks, sb is already counted in previous macros).
+ */
+ credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
+ EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
+ EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);
+ }
retry:
- handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
- EXT4_INDEX_EXTRA_TRANS_BLOCKS + 5 +
- EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb));
+ handle = ext4_journal_start(dir, credits);
if (IS_ERR(handle))
return PTR_ERR(handle);
@@ -2273,21 +2290,44 @@ retry:
if (IS_ERR(inode))
goto out_stop;
- if (l > sizeof(EXT4_I(inode)->i_data)) {
+ if (l > EXT4_N_BLOCKS * 4) {
inode->i_op = &ext4_symlink_inode_operations;
ext4_set_aops(inode);
/*
- * page_symlink() calls into ext4_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 ext4_write_begin() which can wait
+ * for transaction commit if we are running out of space
+ * and thus we deadlock. 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 = ext4_orphan_add(handle, inode);
+ ext4_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 (EXT4_DATA_TRANS_BLOCKS
+ * + EXT4_INDEX_EXTRA_TRANS_BLOCKS), inode is also modified
+ */
+ handle = ext4_journal_start(dir,
+ EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
+ EXT4_INDEX_EXTRA_TRANS_BLOCKS + 1);
+ if (IS_ERR(handle)) {
+ err = PTR_ERR(handle);
+ goto err_drop_inode;
+ }
+ inc_nlink(inode);
+ err = ext4_orphan_del(handle, inode);
if (err) {
+ ext4_journal_stop(handle);
clear_nlink(inode);
- unlock_new_inode(inode);
- ext4_mark_inode_dirty(handle, inode);
- iput(inode);
- goto out_stop;
+ goto err_drop_inode;
}
} else {
/* clear the extent format for fast symlink */
@@ -2303,6 +2343,10 @@ out_stop:
if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
goto retry;
return err;
+err_drop_inode:
+ unlock_new_inode(inode);
+ iput(inode);
+ return err;
}
static int ext4_link(struct dentry *old_dentry,