f2fs: support direct I/O with fscrypt using blk-crypto

Encrypted files traditionally haven't supported DIO, due to the need to
encrypt/decrypt the data.  However, when the encryption is implemented
using inline encryption (blk-crypto) instead of the traditional
filesystem-layer encryption, it is straightforward to support DIO.

Therefore, make f2fs support DIO on files that are using inline
encryption.  Since f2fs uses iomap for DIO, and fscrypt support was
already added to iomap DIO, this just requires two small changes:

- Let DIO proceed when supported, by checking fscrypt_dio_supported()
  instead of assuming that encrypted files never support DIO.

- In f2fs_iomap_begin(), use fscrypt_limit_io_blocks() to limit the
  length of the mapping in the rare case where a DUN discontiguity
  occurs in the middle of an extent.  The iomap DIO implementation
  requires this, since it assumes that it can submit a bio covering (up
  to) the whole mapping, without checking fscrypt constraints itself.

Co-developed-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>
Link: https://lore.kernel.org/r/20220128233940.79464-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8c417864c66ae3b5abdfbe0138cda383e71f9684..020d47f97969cde258009394e2c3fe6a7a737940 100644 (file)
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -4044,6 +4044,13 @@ static int f2fs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 
        iomap->offset = blks_to_bytes(inode, map.m_lblk);
 
+       /*
+        * When inline encryption is enabled, sometimes I/O to an encrypted file
+        * has to be broken up to guarantee DUN contiguity.  Handle this by
+        * limiting the length of the mapping returned.
+        */
+       map.m_len = fscrypt_limit_io_blocks(inode, map.m_lblk, map.m_len);
+
        if (map.m_flags & (F2FS_MAP_MAPPED | F2FS_MAP_UNWRITTEN)) {
                iomap->length = blks_to_bytes(inode, map.m_len);
                if (map.m_flags & F2FS_MAP_MAPPED) {

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 68b44015514f51834b2c63b13bb37fb98d228bd3..8130b092e5432a8b6c3d9db475238e701577d876 100644 (file)
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4371,7 +4371,11 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
        struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
        int rw = iov_iter_rw(iter);
 
-       if (f2fs_post_read_required(inode))
+       if (!fscrypt_dio_supported(iocb, iter))
+               return true;
+       if (fsverity_active(inode))
+               return true;
+       if (f2fs_compressed_file(inode))
                return true;
 
        /* disallow direct IO if any of devices has unaligned blksize */