Commit b1b4705d authored by Matthew Bobrowski's avatar Matthew Bobrowski Committed by Theodore Ts'o

ext4: introduce direct I/O read using iomap infrastructure

This patch introduces a new direct I/O read path which makes use of
the iomap infrastructure.

The new function ext4_do_read_iter() is responsible for calling into
the iomap infrastructure via iomap_dio_rw(). If the read operation
performed on the inode is not supported, which is checked via
ext4_dio_supported(), then we simply fallback and complete the I/O
using buffered I/O.

Existing direct I/O read code path has been removed, as it is now
redundant.
Signed-off-by: default avatarMatthew Bobrowski <mbobrowski@mbobrowski.org>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarRitesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/f98a6f73fadddbfbad0fc5ed04f712ca0b799f37.1572949325.git.mbobrowski@mbobrowski.orgSigned-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 09edf4d3
......@@ -34,6 +34,52 @@
#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);
if (iocb->ki_flags & IOCB_NOWAIT) {
if (!inode_trylock_shared(inode))
return -EAGAIN;
} else {
inode_lock_shared(inode);
}
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 within 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,
is_sync_kiocb(iocb));
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 +110,21 @@ 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);
}
......
......@@ -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);
}
......@@ -3916,36 +3913,6 @@ 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.
*/
if (iocb->ki_flags & IOCB_NOWAIT) {
if (!inode_trylock_shared(inode))
return -EAGAIN;
} else {
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;
......@@ -3972,10 +3939,7 @@ 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;
}
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment