| Message ID | 20200905052023.3719585-4-krisman@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Unaligned DIO read error path fix and clean ups | expand |
On Sat 05-09-20 01:20:23, Gabriel Krisman Bertazi wrote: > Prior to commit 9fe55eea7e4b ("Fix race when checking i_size on direct > i/o read"), an unaligned direct read past end of file would trigger EOF, > since generic_file_aio_read detected this read-at-EOF condition and > skipped the direct IO read entirely, returning 0. After that change, the > read now reaches dio_generic, which detects the misalignment and returns > EINVAL. > > This consolidates the generic direct-io to follow the same behavior of > filesystems. Apparently, this fix will only affect ocfs2 since other > filesystems do this verification before calling do_blockdev_direct_IO, > with the exception of f2fs, which has the same bug, but is fixed in the > next patch. > > it can be verified by a read loop on a file that does a partial read > before EOF (On file that doesn't end at an aligned address). The > following code fails on an unaligned file on filesystems without > prior validation without this patch, but not on btrfs, ext4, and xfs. > > while (done < total) { > ssize_t delta = pread(fd, buf + done, total - done, off + done); > if (!delta) > break; > ... > } > > Fix this regression by moving the misalignment check to after the EOF > check added by commit 74cedf9b6c60 ("direct-io: Fix negative return from > dio read beyond eof"). > > Based on a patch by Jamie Liu. > > Reported-by: Jamie Liu <jamieliu@google.com> > Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> The patch looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > fs/direct-io.c | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/fs/direct-io.c b/fs/direct-io.c > index c17efe58f1c9..82838cca934b 100644 > --- a/fs/direct-io.c > +++ b/fs/direct-io.c > @@ -1165,14 +1165,6 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, > * the early prefetch in the caller enough time. > */ > > - if (align & blocksize_mask) { > - if (bdev) > - blkbits = blksize_bits(bdev_logical_block_size(bdev)); > - blocksize_mask = (1 << blkbits) - 1; > - if (align & blocksize_mask) > - return -EINVAL; > - } > - > /* watch out for a 0 len io from a tricksy fs */ > if (iov_iter_rw(iter) == READ && !count) > return 0; > @@ -1200,6 +1192,14 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, > goto fail_dio; > } > > + if (align & blocksize_mask) { > + if (bdev) > + blkbits = blksize_bits(bdev_logical_block_size(bdev)); > + blocksize_mask = (1 << blkbits) - 1; > + if (align & blocksize_mask) > + goto fail_dio; > + } > + > if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { > struct address_space *mapping = iocb->ki_filp->f_mapping; > > -- > 2.28.0 >
diff --git a/fs/direct-io.c b/fs/direct-io.c index c17efe58f1c9..82838cca934b 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -1165,14 +1165,6 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, * the early prefetch in the caller enough time. */ - if (align & blocksize_mask) { - if (bdev) - blkbits = blksize_bits(bdev_logical_block_size(bdev)); - blocksize_mask = (1 << blkbits) - 1; - if (align & blocksize_mask) - return -EINVAL; - } - /* watch out for a 0 len io from a tricksy fs */ if (iov_iter_rw(iter) == READ && !count) return 0; @@ -1200,6 +1192,14 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, goto fail_dio; } + if (align & blocksize_mask) { + if (bdev) + blkbits = blksize_bits(bdev_logical_block_size(bdev)); + blocksize_mask = (1 << blkbits) - 1; + if (align & blocksize_mask) + goto fail_dio; + } + if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { struct address_space *mapping = iocb->ki_filp->f_mapping;
Prior to commit 9fe55eea7e4b ("Fix race when checking i_size on direct i/o read"), an unaligned direct read past end of file would trigger EOF, since generic_file_aio_read detected this read-at-EOF condition and skipped the direct IO read entirely, returning 0. After that change, the read now reaches dio_generic, which detects the misalignment and returns EINVAL. This consolidates the generic direct-io to follow the same behavior of filesystems. Apparently, this fix will only affect ocfs2 since other filesystems do this verification before calling do_blockdev_direct_IO, with the exception of f2fs, which has the same bug, but is fixed in the next patch. it can be verified by a read loop on a file that does a partial read before EOF (On file that doesn't end at an aligned address). The following code fails on an unaligned file on filesystems without prior validation without this patch, but not on btrfs, ext4, and xfs. while (done < total) { ssize_t delta = pread(fd, buf + done, total - done, off + done); if (!delta) break; ... } Fix this regression by moving the misalignment check to after the EOF check added by commit 74cedf9b6c60 ("direct-io: Fix negative return from dio read beyond eof"). Based on a patch by Jamie Liu. Reported-by: Jamie Liu <jamieliu@google.com> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> --- fs/direct-io.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)