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authorMatthew Bobrowski <mbobrowski@mbobrowski.org>2019-11-05 23:01:37 +1100
committerTheodore Ts'o <tytso@mit.edu>2019-11-05 11:31:40 -0500
commitb1b4705d54abedfd69dcdf42779c521aa1e0fbd3 (patch)
treed9790309bb21a76ac01da60b907a0631b4e80704 /fs/ext4/file.c
parent09edf4d381957b144440bac18a4769c53063b943 (diff)
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: 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>
Diffstat (limited to 'fs/ext4/file.c')
-rw-r--r--fs/ext4/file.c55
1 files changed, 53 insertions, 2 deletions
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index ab75aee3e687..440f4c6ba4ee 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -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);
}