From 46d716025a228de835a8fd51c8420e3ce3c88795 Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Thu, 8 Oct 2020 02:26:18 -0400 Subject: [PATCH 1/3] direct-io: clean up error paths of do_blockdev_direct_IO In preparation to resort DIO checks, reduce code duplication of error handling in do_blockdev_direct_IO. Link: https://lore.kernel.org/r/20201008062620.2928326-2-krisman@collabora.com Reviewed-by: Jan Kara Reviewed-by: Jens Axboe Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Jan Kara --- fs/direct-io.c | 35 ++++++++++++++--------------------- 1 file changed, 14 insertions(+), 21 deletions(-) diff --git a/fs/direct-io.c b/fs/direct-io.c index 183299892465..6c11db1cec27 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -1170,7 +1170,7 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, blkbits = blksize_bits(bdev_logical_block_size(bdev)); blocksize_mask = (1 << blkbits) - 1; if (align & blocksize_mask) - goto out; + return -EINVAL; } /* watch out for a 0 len io from a tricksy fs */ @@ -1178,9 +1178,8 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, return 0; dio = kmem_cache_alloc(dio_cache, GFP_KERNEL); - retval = -ENOMEM; if (!dio) - goto out; + return -ENOMEM; /* * Believe it or not, zeroing out the page array caused a .5% * performance regression in a database benchmark. So, we take @@ -1199,22 +1198,16 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, retval = filemap_write_and_wait_range(mapping, offset, end - 1); - if (retval) { - inode_unlock(inode); - kmem_cache_free(dio_cache, dio); - goto out; - } + if (retval) + goto fail_dio; } } /* Once we sampled i_size check for reads beyond EOF */ dio->i_size = i_size_read(inode); if (iov_iter_rw(iter) == READ && offset >= dio->i_size) { - if (dio->flags & DIO_LOCKING) - inode_unlock(inode); - kmem_cache_free(dio_cache, dio); retval = 0; - goto out; + goto fail_dio; } /* @@ -1258,14 +1251,8 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, */ retval = sb_init_dio_done_wq(dio->inode->i_sb); } - if (retval) { - /* - * We grab i_mutex only for reads so we don't have - * to release it here - */ - kmem_cache_free(dio_cache, dio); - goto out; - } + if (retval) + goto fail_dio; } /* @@ -1368,7 +1355,13 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, } else BUG_ON(retval != -EIOCBQUEUED); -out: + return retval; + +fail_dio: + if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) + inode_unlock(inode); + + kmem_cache_free(dio_cache, dio); return retval; } From 0a9164cb7ff32d6936f14657aebc3c4c2a0d5f9d Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Thu, 8 Oct 2020 02:26:19 -0400 Subject: [PATCH 2/3] direct-io: don't force writeback for reads beyond EOF If a DIO read starts past EOF, the kernel won't attempt it, so we don't need to flush dirty pages before failing the syscall. Link: https://lore.kernel.org/r/20201008062620.2928326-3-krisman@collabora.com Suggested-by: Jan Kara Reviewed-by: Jan Kara Reviewed-by: Jens Axboe Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Jan Kara --- fs/direct-io.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) diff --git a/fs/direct-io.c b/fs/direct-io.c index 6c11db1cec27..c17efe58f1c9 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -1188,19 +1188,9 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, memset(dio, 0, offsetof(struct dio, pages)); dio->flags = flags; - if (dio->flags & DIO_LOCKING) { - if (iov_iter_rw(iter) == READ) { - struct address_space *mapping = - iocb->ki_filp->f_mapping; - - /* will be released by direct_io_worker */ - inode_lock(inode); - - retval = filemap_write_and_wait_range(mapping, offset, - end - 1); - if (retval) - goto fail_dio; - } + if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { + /* will be released by direct_io_worker */ + inode_lock(inode); } /* Once we sampled i_size check for reads beyond EOF */ @@ -1210,6 +1200,14 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, goto fail_dio; } + if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { + struct address_space *mapping = iocb->ki_filp->f_mapping; + + retval = filemap_write_and_wait_range(mapping, offset, end - 1); + if (retval) + goto fail_dio; + } + /* * For file extending writes updating i_size before data writeouts * complete can expose uninitialized blocks in dumb filesystems. From 41b21af388f94baf7433d4e7845703c7275251de Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Thu, 8 Oct 2020 02:26:20 -0400 Subject: [PATCH 3/3] direct-io: defer alignment check until after the EOF check 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. Link: https://lore.kernel.org/r/20201008062620.2928326-4-krisman@collabora.com Reported-by: Jamie Liu Reviewed-by: Jan Kara Reviewed-by: Jens Axboe Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Jan Kara --- 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;