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Date: Tue, 1 Nov 2016 22:06:16 +0100
From: Jan Kara <jack@...e.cz>
To: linux-ext4@...r.kernel.org
Cc: Ted Tso <tytso@....edu>, linux-fsdevel@...r.kernel.org,
linux-nvdimm@...ts.01.org, Dave Chinner <david@...morbit.com>,
Jan Kara <jack@...e.cz>
Subject: [PATCH 06/11] ext4: DAX iomap write support
Implement DAX writes using the new iomap infrastructure instead of
overloading the direct IO path.
Signed-off-by: Jan Kara <jack@...e.cz>
---
fs/ext4/file.c | 39 ++++++++++++++++++++++--
fs/ext4/inode.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 125 insertions(+), 8 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 28ebc2418dc2..d7ab0e90d1b8 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -172,6 +172,39 @@ static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
}
static ssize_t
+ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ ssize_t ret;
+ bool overwrite = false;
+
+ inode_lock(inode);
+ ret = ext4_write_checks(iocb, from);
+ if (ret <= 0)
+ goto out;
+ ret = file_remove_privs(iocb->ki_filp);
+ if (ret)
+ goto out;
+ ret = file_update_time(iocb->ki_filp);
+ if (ret)
+ goto out;
+
+ if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {
+ overwrite = true;
+ downgrade_write(&inode->i_rwsem);
+ }
+ ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
+out:
+ if (!overwrite)
+ inode_unlock(inode);
+ else
+ inode_unlock_shared(inode);
+ if (ret > 0)
+ ret = generic_write_sync(iocb, ret);
+ return ret;
+}
+
+static ssize_t
ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
@@ -180,6 +213,9 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
int overwrite = 0;
ssize_t ret;
+ if (IS_DAX(inode))
+ return ext4_dax_write_iter(iocb, from);
+
inode_lock(inode);
ret = ext4_write_checks(iocb, from);
if (ret <= 0)
@@ -199,8 +235,7 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
iocb->private = &overwrite;
/* Check whether we do a DIO overwrite or not */
- if (((o_direct && !unaligned_aio) || IS_DAX(inode)) &&
- ext4_should_dioread_nolock(inode) &&
+ if ((o_direct && !unaligned_aio) && ext4_should_dioread_nolock(inode) &&
ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from)))
overwrite = 1;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ac26a390f14c..d07d003ebce2 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3316,18 +3316,62 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
struct ext4_map_blocks map;
int ret;
- if (flags & IOMAP_WRITE)
- return -EIO;
-
if (WARN_ON_ONCE(ext4_has_inline_data(inode)))
return -ERANGE;
map.m_lblk = first_block;
map.m_len = last_block - first_block + 1;
- ret = ext4_map_blocks(NULL, inode, &map, 0);
- if (ret < 0)
- return ret;
+ if (!(flags & IOMAP_WRITE)) {
+ ret = ext4_map_blocks(NULL, inode, &map, 0);
+ } else {
+ int dio_credits;
+ handle_t *handle;
+ int retries = 0;
+
+ /* Trim mapping request to maximum we can map at once for DIO */
+ if (map.m_len > DIO_MAX_BLOCKS)
+ map.m_len = DIO_MAX_BLOCKS;
+ dio_credits = ext4_chunk_trans_blocks(inode, map.m_len);
+retry:
+ /*
+ * Either we allocate blocks and then we don't get unwritten
+ * extent so we have reserved enough credits, or the blocks
+ * are already allocated and unwritten and in that case
+ * extent conversion fits in the credits as well.
+ */
+ handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS,
+ dio_credits);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+
+ ret = ext4_map_blocks(handle, inode, &map,
+ EXT4_GET_BLOCKS_PRE_IO |
+ EXT4_GET_BLOCKS_CREATE_ZERO);
+ if (ret < 0) {
+ ext4_journal_stop(handle);
+ if (ret == -ENOSPC &&
+ ext4_should_retry_alloc(inode->i_sb, &retries))
+ goto retry;
+ return ret;
+ }
+ /* For DAX writes we need to zero out unwritten extents */
+ if (map.m_flags & EXT4_MAP_UNWRITTEN) {
+ /*
+ * We are protected by i_mmap_sem or i_rwsem so we know
+ * block cannot go away from under us even though we
+ * dropped i_data_sem. Convert extent to written and
+ * write zeros there.
+ */
+ ret = ext4_map_blocks(handle, inode, &map,
+ EXT4_GET_BLOCKS_CONVERT |
+ EXT4_GET_BLOCKS_CREATE_ZERO);
+ if (ret < 0) {
+ ext4_journal_stop(handle);
+ return ret;
+ }
+ }
+ }
iomap->flags = 0;
iomap->bdev = inode->i_sb->s_bdev;
@@ -3355,8 +3399,46 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
return 0;
}
+static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
+ ssize_t written, unsigned flags, struct iomap *iomap)
+{
+ if (flags & IOMAP_WRITE) {
+ handle_t *handle = ext4_journal_current_handle();
+ ext4_lblk_t written_blk, end_blk;
+ int blkbits = inode->i_blkbits;
+ bool truncate = false;
+
+ if (ext4_update_inode_size(inode, offset + written))
+ ext4_mark_inode_dirty(handle, inode);
+ written_blk = (offset + written) >> blkbits;
+ end_blk = (offset + length) >> blkbits;
+ /*
+ * We may need to truncate allocated but not written blocks
+ * beyond EOF.
+ */
+ if (written_blk < end_blk && offset + length > inode->i_size &&
+ ext4_can_truncate(inode)) {
+ ext4_orphan_add(handle, inode);
+ truncate = true;
+ }
+ ext4_journal_stop(handle);
+ if (truncate) {
+ ext4_truncate_failed_write(inode);
+ /*
+ * If truncate failed early the inode might still be
+ * on the orphan list; we need to make sure the inode
+ * is removed from the orphan list in that case.
+ */
+ if (inode->i_nlink)
+ ext4_orphan_del(NULL, inode);
+ }
+ }
+ return 0;
+}
+
struct iomap_ops ext4_iomap_ops = {
.iomap_begin = ext4_iomap_begin,
+ .iomap_end = ext4_iomap_end,
};
#else
--
2.6.6
--
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