3.16.83-rc1 review patch. If anyone has any objections, please let me know.
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From: Jan Kara jack@suse.com
commit 17048e8a083fec7ad841d88ef0812707fbc7e39f upstream.
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 jack@suse.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Ben Hutchings ben@decadent.org.uk --- fs/ext4/extents.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-)
--- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4707,10 +4707,6 @@ static int ext4_alloc_file_blocks(struct 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 */ @@ -4760,8 +4756,6 @@ retry: goto retry; }
- ext4_inode_resume_unlocked_dio(inode); - return ret > 0 ? ret2 : ret; }
@@ -4836,6 +4830,10 @@ static long ext4_zero_range(struct file 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, @@ -4844,7 +4842,7 @@ static long ext4_zero_range(struct file round_down(offset, 1 << blkbits)) >> blkbits, new_size, flags, mode); if (ret) - goto out_mutex; + goto out_dio;
}
@@ -4853,10 +4851,6 @@ static long ext4_zero_range(struct file 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. @@ -4985,8 +4979,13 @@ long ext4_fallocate(struct file *file, i 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;