ext4: use transaction reservation for extent conversion in ext4_end_io
Later we would like to clear PageWriteback bit only after extent
conversion from unwritten to written extents is performed. However it
is not possible to start a transaction after PageWriteback is set
because that violates lock ordering (and is easy to deadlock). So we
have to reserve a transaction before locking pages and sending them
for IO and later we use the transaction for extent conversion from
ext4_end_io().
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 94283d0..208f664 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4566,10 +4566,9 @@
* function, to convert the fallocated extents after IO is completed.
* Returns 0 on success.
*/
-int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
- ssize_t len)
+int ext4_convert_unwritten_extents(handle_t *handle, struct inode *inode,
+ loff_t offset, ssize_t len)
{
- handle_t *handle;
unsigned int max_blocks;
int ret = 0;
int ret2 = 0;
@@ -4584,16 +4583,32 @@
max_blocks = ((EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits) -
map.m_lblk);
/*
- * credits to insert 1 extent into extent tree
+ * This is somewhat ugly but the idea is clear: When transaction is
+ * reserved, everything goes into it. Otherwise we rather start several
+ * smaller transactions for conversion of each extent separately.
*/
- credits = ext4_chunk_trans_blocks(inode, max_blocks);
+ if (handle) {
+ handle = ext4_journal_start_reserved(handle,
+ EXT4_HT_EXT_CONVERT);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+ credits = 0;
+ } else {
+ /*
+ * credits to insert 1 extent into extent tree
+ */
+ credits = ext4_chunk_trans_blocks(inode, max_blocks);
+ }
while (ret >= 0 && ret < max_blocks) {
map.m_lblk += ret;
map.m_len = (max_blocks -= ret);
- handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS, credits);
- if (IS_ERR(handle)) {
- ret = PTR_ERR(handle);
- break;
+ if (credits) {
+ handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS,
+ credits);
+ if (IS_ERR(handle)) {
+ ret = PTR_ERR(handle);
+ break;
+ }
}
ret = ext4_map_blocks(handle, inode, &map,
EXT4_GET_BLOCKS_IO_CONVERT_EXT);
@@ -4604,10 +4619,13 @@
inode->i_ino, map.m_lblk,
map.m_len, ret);
ext4_mark_inode_dirty(handle, inode);
- ret2 = ext4_journal_stop(handle);
- if (ret <= 0 || ret2 )
+ if (credits)
+ ret2 = ext4_journal_stop(handle);
+ if (ret <= 0 || ret2)
break;
}
+ if (!credits)
+ ret2 = ext4_journal_stop(handle);
return ret > 0 ? ret2 : ret;
}