ext4: add a new nolock flag in ext4_map_blocks
EXT4_GET_BLOCKS_NO_LOCK flag is added to indicate that we don't need
to acquire i_data_sem lock in ext4_map_blocks. Meanwhile, it changes
ext4_get_block() to not start a new journal because when we do a
overwrite dio, there is no any metadata that needs to be modified.
We define a new function called ext4_get_block_write_nolock, which is
used in dio overwrite nolock. In this function, it doesn't try to
acquire i_data_sem lock and doesn't start a new journal as it does a
lookup.
CC: Tao Ma <tm@tao.ma>
CC: Eric Sandeen <sandeen@redhat.com>
CC: Robin Dong <hao.bigrat@gmail.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 01434f2..4a49f82 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -571,6 +571,8 @@
#define EXT4_GET_BLOCKS_NO_NORMALIZE 0x0040
/* Request will not result in inode size update (user for fallocate) */
#define EXT4_GET_BLOCKS_KEEP_SIZE 0x0080
+ /* Do not take i_data_sem locking in ext4_map_blocks */
+#define EXT4_GET_BLOCKS_NO_LOCK 0x0100
/*
* Flags used by ext4_free_blocks
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 02bc8cb..76cb3b1 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -544,7 +544,8 @@
* Try to see if we can get the block without requesting a new
* file system block.
*/
- down_read((&EXT4_I(inode)->i_data_sem));
+ if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))
+ down_read((&EXT4_I(inode)->i_data_sem));
if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
retval = ext4_ext_map_blocks(handle, inode, map, flags &
EXT4_GET_BLOCKS_KEEP_SIZE);
@@ -552,7 +553,8 @@
retval = ext4_ind_map_blocks(handle, inode, map, flags &
EXT4_GET_BLOCKS_KEEP_SIZE);
}
- up_read((&EXT4_I(inode)->i_data_sem));
+ if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))
+ up_read((&EXT4_I(inode)->i_data_sem));
if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
int ret = check_block_validity(inode, map);
@@ -2818,6 +2820,32 @@
EXT4_GET_BLOCKS_IO_CREATE_EXT);
}
+static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock,
+ struct buffer_head *bh_result, int flags)
+{
+ handle_t *handle = ext4_journal_current_handle();
+ struct ext4_map_blocks map;
+ int ret = 0;
+
+ ext4_debug("ext4_get_block_write_nolock: inode %lu, flag %d\n",
+ inode->i_ino, flags);
+
+ flags = EXT4_GET_BLOCKS_NO_LOCK;
+
+ map.m_lblk = iblock;
+ map.m_len = bh_result->b_size >> inode->i_blkbits;
+
+ ret = ext4_map_blocks(handle, inode, &map, flags);
+ if (ret > 0) {
+ map_bh(bh_result, inode->i_sb, map.m_pblk);
+ bh_result->b_state = (bh_result->b_state & ~EXT4_MAP_FLAGS) |
+ map.m_flags;
+ bh_result->b_size = inode->i_sb->s_blocksize * map.m_len;
+ ret = 0;
+ }
+ return ret;
+}
+
static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
ssize_t size, void *private, int ret,
bool is_async)
@@ -2966,6 +2994,8 @@
loff_t final_size = offset + count;
if (rw == WRITE && final_size <= inode->i_size) {
+ int overwrite = 0;
+
/*
* We could direct write to holes and fallocate.
*
@@ -3005,13 +3035,22 @@
EXT4_I(inode)->cur_aio_dio = iocb->private;
}
- ret = __blockdev_direct_IO(rw, iocb, inode,
- inode->i_sb->s_bdev, iov,
- offset, nr_segs,
- ext4_get_block_write,
- ext4_end_io_dio,
- NULL,
- DIO_LOCKING);
+ if (overwrite)
+ ret = __blockdev_direct_IO(rw, iocb, inode,
+ inode->i_sb->s_bdev, iov,
+ offset, nr_segs,
+ ext4_get_block_write_nolock,
+ ext4_end_io_dio,
+ NULL,
+ 0);
+ else
+ ret = __blockdev_direct_IO(rw, iocb, inode,
+ inode->i_sb->s_bdev, iov,
+ offset, nr_segs,
+ ext4_get_block_write,
+ ext4_end_io_dio,
+ NULL,
+ DIO_LOCKING);
if (iocb->private)
EXT4_I(inode)->cur_aio_dio = NULL;
/*
@@ -3031,7 +3070,7 @@
if (ret != -EIOCBQUEUED && ret <= 0 && iocb->private) {
ext4_free_io_end(iocb->private);
iocb->private = NULL;
- } else if (ret > 0 && ext4_test_inode_state(inode,
+ } else if (ret > 0 && !overwrite && ext4_test_inode_state(inode,
EXT4_STATE_DIO_UNWRITTEN)) {
int err;
/*