[RFC PATCH 3/7] ext4: support STATX_IOALIGN

Eric Biggers
2022-02-11T06:14:02Z

Add support for STATX_IOALIGN to ext4, so that I/O alignment information
is exposed to userspace in a consistent and easy-to-use way.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/ext4/ext4.h | 1 +
fs/ext4/file.c | 15 ++++-----------
fs/ext4/inode.c | 31 +++++++++++++++++++++++++++++++
3 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index bcd3b9bf8069b..fcab9713005fa 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3014,6 +3014,7 @@ extern struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
extern int ext4_write_inode(struct inode *, struct writeback_control *);
extern int ext4_setattr(struct user_namespace *, struct dentry *,
struct iattr *);
+extern u32 ext4_dio_alignment(struct inode *inode);
extern int ext4_getattr(struct user_namespace *, const struct path *,
struct kstat *, u32, unsigned int);
extern void ext4_evict_inode(struct inode *);
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index b68706f7db439..9c34f827a021f 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -39,19 +39,12 @@
static bool ext4_dio_supported(struct kiocb *iocb, struct iov_iter *iter)
{
struct inode *inode = file_inode(iocb->ki_filp);
+ u32 dio_align = ext4_dio_alignment(inode);

- if (IS_ENCRYPTED(inode)) {
- if (!fscrypt_dio_supported(inode))
- return false;
- if (!IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(iter),
- i_blocksize(inode)))
- return false;
- }
- if (fsverity_active(inode))
- return false;
- if (ext4_should_journal_data(inode))
+ if (!dio_align)
return false;
- if (ext4_has_inline_data(inode))
+ if (dio_align > bdev_logical_block_size(inode->i_sb->s_bdev) &&
+ !IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(iter), dio_align))
return false;
return true;
}
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4cf55ef54193a..8c9d124a6378c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5493,6 +5493,22 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
return error;
}

+u32 ext4_dio_alignment(struct inode *inode)
+{
+ if (fsverity_active(inode))
+ return 0;
+ if (ext4_should_journal_data(inode))
+ return 0;
+ if (ext4_has_inline_data(inode))
+ return 0;
+ if (IS_ENCRYPTED(inode)) {
+ if (!fscrypt_dio_supported(inode))
+ return 0;
+ return i_blocksize(inode);
+ }
+ return bdev_logical_block_size(inode->i_sb->s_bdev);
+}
+
int ext4_getattr(struct user_namespace *mnt_userns, const struct path *path,
struct kstat *stat, u32 request_mask, unsigned int query_flags)
{
@@ -5508,6 +5524,21 @@ int ext4_getattr(struct user_namespace *mnt_userns, const struct path *path,
stat->btime.tv_nsec = ei->i_crtime.tv_nsec;
}

+ /*
+ * Return the I/O alignment information if requested. We only return
+ * this information when requested, since on encrypted files it might
+ * take a fair bit of work to get if the file wasn't opened recently.
+ */
+ if ((request_mask & STATX_IOALIGN) && S_ISREG(inode->i_mode)) {
+ u32 dio_align = ext4_dio_alignment(inode);
+ unsigned int io_opt = bdev_io_opt(inode->i_sb->s_bdev);
+
+ stat->result_mask |= STATX_IOALIGN;
+ stat->mem_align_dio = dio_align;
+ stat->offset_align_dio = dio_align;
+ stat->offset_align_optimal = max(io_opt, i_blocksize(inode));
+ }
+
flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
if (flags & EXT4_APPEND_FL)
stat->attributes |= STATX_ATTR_APPEND;
--
2.35.1