On 10/3/19 5:04 PM, Matthew Bobrowski wrote:
This patch introduces a new direct I/O read path that makes use of the
iomap infrastructure.
The new function ext4_dio_read_iter() is responsible for calling into
the iomap infrastructure via iomap_dio_rw(). If the read operation
being performed on the inode does not pass the preliminary checks
performed within ext4_dio_supported(), then we simply fallback to
buffered I/O in order to fulfil the request.
Existing direct I/O read buffer_head code has been removed as it's now
redundant.
Signed-off-by: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx>
---
fs/ext4/file.c | 58 +++++++++++++++++++++++++++++++++++++++++++++----
fs/ext4/inode.c | 32 +--------------------------
2 files changed, 55 insertions(+), 35 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index ab75aee3e687..69ac042fb74b 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -34,6 +34,53 @@
#include "xattr.h"
#include "acl.h"
+static bool ext4_dio_supported(struct inode *inode)
+{
+ if (IS_ENABLED(CONFIG_FS_ENCRYPTION) && IS_ENCRYPTED(inode))
+ return false;
+ if (fsverity_active(inode))
+ return false;
+ if (ext4_should_journal_data(inode))
+ return false;
+ if (ext4_has_inline_data(inode))
+ return false;
+ return true;
+}
+
+static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ ssize_t ret;
+ struct inode *inode = file_inode(iocb->ki_filp);
+
+ /*
+ * Get exclusion from truncate and other inode operations.
+ */
+ if (!inode_trylock_shared(inode)) {
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ return -EAGAIN;
+ inode_lock_shared(inode);
+ }
Same comments here.
Let's follow as per the discussion here
https://patchwork.kernel.org/patch/11141577/
+
+ if (!ext4_dio_supported(inode)) {
+ inode_unlock_shared(inode);
+ /*
+ * Fallback to buffered I/O if the operation being
+ * performed on the inode is not supported by direct
+ * I/O. The IOCB_DIRECT flag needs to be cleared here
+ * in order to ensure that the direct I/O path withiin
+ * generic_file_read_iter() is not taken.
+ */
+ iocb->ki_flags &= ~IOCB_DIRECT;
+ return generic_file_read_iter(iocb, to);
+ }
+
+ ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL);
+ inode_unlock_shared(inode);
+
+ file_accessed(iocb->ki_filp);
+ return ret;
+}
+
#ifdef CONFIG_FS_DAX
static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
@@ -64,16 +111,19 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
- if (unlikely(ext4_forced_shutdown(EXT4_SB(file_inode(iocb->ki_filp)->i_sb))))
+ struct inode *inode = file_inode(iocb->ki_filp);
+
+ if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
return -EIO;
if (!iov_iter_count(to))
return 0; /* skip atime */
-#ifdef CONFIG_FS_DAX
- if (IS_DAX(file_inode(iocb->ki_filp)))
+ if (IS_DAX(inode))
return ext4_dax_read_iter(iocb, to);
-#endif
+
+ if (iocb->ki_flags & IOCB_DIRECT)
+ return ext4_dio_read_iter(iocb, to);
return generic_file_read_iter(iocb, to);
}
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1dace576b8bd..159ffb92f82d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -863,9 +863,6 @@ int ext4_dio_get_block(struct inode *inode, sector_t iblock,
{
/* We don't expect handle for direct IO */
WARN_ON_ONCE(ext4_journal_current_handle());
-
- if (!create)
- return _ext4_get_block(inode, iblock, bh, 0);
return ext4_get_block_trans(inode, iblock, bh, EXT4_GET_BLOCKS_CREATE);
}
@@ -3855,30 +3852,6 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
return ret;
}
-static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter)
-{
- struct address_space *mapping = iocb->ki_filp->f_mapping;
- struct inode *inode = mapping->host;
- size_t count = iov_iter_count(iter);
- ssize_t ret;
-
- /*
- * Shared inode_lock is enough for us - it protects against concurrent
- * writes & truncates and since we take care of writing back page cache,
- * we are protected against page writeback as well.
- */
- inode_lock_shared(inode);
- ret = filemap_write_and_wait_range(mapping, iocb->ki_pos,
- iocb->ki_pos + count - 1);
- if (ret)
- goto out_unlock;
- ret = __blockdev_direct_IO(iocb, inode, inode->i_sb->s_bdev,
- iter, ext4_dio_get_block, NULL, NULL, 0);
-out_unlock:
- inode_unlock_shared(inode);
- return ret;
-}
-
static ssize_t ext4_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
@@ -3905,10 +3878,7 @@ static ssize_t ext4_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
return 0;
trace_ext4_direct_IO_enter(inode, offset, count, iov_iter_rw(iter));
- if (iov_iter_rw(iter) == READ)
- ret = ext4_direct_IO_read(iocb, iter);
- else
- ret = ext4_direct_IO_write(iocb, iter);
+ ret = ext4_direct_IO_write(iocb, iter);
trace_ext4_direct_IO_exit(inode, offset, count, iov_iter_rw(iter), ret);
return ret;
}
