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ext4: introduce direct I/O read using iomap infrastructure

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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: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/f98a6f73fadddbfbad0fc5ed04f712ca0b799f37.1572949325.git.mbobrowski@mbobrowski.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Matthew Bobrowski
2019-11-05 23:01:37 +11:00
committed by Theodore Ts'o
parent 09edf4d381
commit b1b4705d54
2 changed files with 54 additions and 39 deletions
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55
fs/ext4/file.c
View File

@@ -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);
}