From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
Aligned and overwrite direct I/O can be parallelized. In ext4_file_dio_write,
we first check whether these conditions are satisfied or not. If so, we
take i_data_sem and release i_mutex lock directly. Meanwhile iocb->private is
set to indicate that this is a dio overwrite, and it will be handled in
ext4_ext_direct_IO.
CC: Tao Ma <tm@xxxxxx>
CC: Eric Sandeen <sandeen@xxxxxxxxxx>
Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
---
fs/ext4/file.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++--
fs/ext4/inode.c | 27 +++++++++++++++++++++++++++
2 files changed, 78 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index a10dc77..812358f 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -93,9 +93,13 @@ static ssize_t
ext4_file_dio_write(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
- struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file->f_mapping->host;
+ struct blk_plug plug;
int unaligned_aio = 0;
ssize_t ret;
+ int overwrite = 0;
+ size_t length = iov_length(iov, nr_segs);
if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
!is_sync_kiocb(iocb))
@@ -115,7 +119,52 @@ ext4_file_dio_write(struct kiocb *iocb, const struct iovec *iov,
ext4_aiodio_wait(inode);
}
- ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
+ BUG_ON(iocb->ki_pos != pos);
+
+ mutex_lock(&inode->i_mutex);
+ blk_start_plug(&plug);
+
+ iocb->private = &overwrite;
+
+ /* check whether we do a DIO overwrite or not */
+ if (ext4_should_dioread_nolock(inode) && !unaligned_aio &&
+ !file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {
+ struct ext4_map_blocks map;
+ unsigned int blkbits = inode->i_blkbits;
+ int err, len;
+
+ map.m_lblk = pos >> blkbits;
+ map.m_len = (EXT4_BLOCK_ALIGN(pos + length, blkbits) >> blkbits)
+ - map.m_lblk;
+ map.m_flags &= ~EXT4_MAP_FLAGS;
+ len = map.m_len;
+
+ err = ext4_map_blocks(NULL, inode, &map, 0);
+ /*
+ * 'err==len' means that all of blocks has been preallocated no
+ * matter they are initialized or not. For excluding
+ * uninitialized extents, we need to check m_flags. There are
+ * two conditions that indicate for initialized extents.
+ * 1) If we hit extent cache, EXT4_MAP_MAPPED flag is returned;
+ * 2) If we do a real lookup, non-flags are returned.
+ * So we should check these two conditions.
+ */
+ if (err == len && (!map.m_flags ||
+ map.m_flags & EXT4_MAP_MAPPED))
+ overwrite = 1;
+ }
+
+ ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
+ mutex_unlock(&inode->i_mutex);
+
+ if (ret > 0 || ret == -EIOCBQUEUED) {
+ ssize_t err;
+
+ err = generic_write_sync(file, pos, ret);
+ if (err < 0 && ret > 0)
+ ret = err;
+ }
+ blk_finish_plug(&plug);
if (unaligned_aio)
mutex_unlock(ext4_aio_mutex(inode));
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9a714ff..98e9096 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2996,6 +2996,26 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
if (rw == WRITE && final_size <= inode->i_size) {
int overwrite = 0;
+ BUG_ON(iocb->private == NULL);
+
+ /* If we do a overwrite dio, i_mutex locking can be released */
+ overwrite = *((int *)iocb->private);
+
+ if (overwrite) {
+ down_read(&EXT4_I(inode)->i_data_sem);
+ mutex_unlock(&inode->i_mutex);
+ }
+
+ /*
+ * If there are still some buffered I/O, we should fall back
+ * to take i_mutex locking.
+ */
+ if (overwrite && file->f_mapping->nrpages) {
+ overwrite = 0;
+ up_read(&EXT4_I(inode)->i_data_sem);
+ mutex_lock(&inode->i_mutex);
+ }
+
/*
* We could direct write to holes and fallocate.
*
@@ -3083,6 +3103,13 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
ret = err;
ext4_clear_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
}
+
+ /* take i_mutex locking again if we do a ovewrite dio */
+ if (overwrite) {
+ up_read(&EXT4_I(inode)->i_data_sem);
+ mutex_lock(&inode->i_mutex);
+ }
+
return ret;
}
--
1.7.4.1
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