From 17048e8a083fec7ad841d88ef0812707fbc7e39f Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 7 Dec 2015 14:29:17 -0500 Subject: [PATCH 2/4] ext4: move unlocked dio protection from ext4_alloc_file_blocks() Currently ext4_alloc_file_blocks() was handling protection against unlocked DIO. However we now need to sometimes call it under i_mmap_sem and sometimes not and DIO protection ranks above it (although strictly speaking this cannot currently create any deadlocks). Also ext4_zero_range() was actually getting & releasing unlocked DIO protection twice in some cases. Luckily it didn't introduce any real bug but it was a land mine waiting to be stepped on. So move DIO protection out from ext4_alloc_file_blocks() into the two callsites. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o --- fs/ext4/extents.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 5be9ca5a8a7a..65b5ada2833f 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4685,10 +4685,6 @@ static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset, if (len <= EXT_UNWRITTEN_MAX_LEN) flags |= EXT4_GET_BLOCKS_NO_NORMALIZE; - /* Wait all existing dio workers, newcomers will block on i_mutex */ - ext4_inode_block_unlocked_dio(inode); - inode_dio_wait(inode); - /* * credits to insert 1 extent into extent tree */ @@ -4752,8 +4748,6 @@ retry: goto retry; } - ext4_inode_resume_unlocked_dio(inode); - return ret > 0 ? ret2 : ret; } @@ -4827,6 +4821,10 @@ static long ext4_zero_range(struct file *file, loff_t offset, if (mode & FALLOC_FL_KEEP_SIZE) flags |= EXT4_GET_BLOCKS_KEEP_SIZE; + /* Wait all existing dio workers, newcomers will block on i_mutex */ + ext4_inode_block_unlocked_dio(inode); + inode_dio_wait(inode); + /* Preallocate the range including the unaligned edges */ if (partial_begin || partial_end) { ret = ext4_alloc_file_blocks(file, @@ -4835,7 +4833,7 @@ static long ext4_zero_range(struct file *file, loff_t offset, round_down(offset, 1 << blkbits)) >> blkbits, new_size, flags, mode); if (ret) - goto out_mutex; + goto out_dio; } @@ -4844,10 +4842,6 @@ static long ext4_zero_range(struct file *file, loff_t offset, flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | EXT4_EX_NOCACHE); - /* Wait all existing dio workers, newcomers will block on i_mutex */ - ext4_inode_block_unlocked_dio(inode); - inode_dio_wait(inode); - /* * Prevent page faults from reinstantiating pages we have * released from page cache. @@ -4992,8 +4986,13 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len) goto out; } + /* Wait all existing dio workers, newcomers will block on i_mutex */ + ext4_inode_block_unlocked_dio(inode); + inode_dio_wait(inode); + ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size, flags, mode); + ext4_inode_resume_unlocked_dio(inode); if (ret) goto out; -- 2.5.5