f2fs: fix to preallocate block only aligned to 4K

In write_begin(), we skip checking dnode block for preallocating block
when whole block needs to be updated since we preallocated its block in
f2fs_preallocate_blocks, for partial updated block, we will still try
to lock its node and do preallocation in write_begin(), so in
f2fs_preallocate_blocks we should not preallocate its block.

But previously, the calculation of preallocating block number is
incorrect, fix it.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
[Jaegeuk Kim: fix a bug]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index ced6beb5debcaa90571161ea4a8958b0009ecd54..7c8e219f93dc338bca7f60e3b5166707b8d0422d 100644 (file)
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -626,7 +626,12 @@ ssize_t f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
        ssize_t ret = 0;
 
        map.m_lblk = F2FS_BLK_ALIGN(iocb->ki_pos);
-       map.m_len = F2FS_BYTES_TO_BLK(iov_iter_count(from));
+       map.m_len = F2FS_BYTES_TO_BLK(iocb->ki_pos + iov_iter_count(from));
+       if (map.m_len > map.m_lblk)
+               map.m_len -= map.m_lblk;
+       else
+               map.m_len = 0;
+
        map.m_next_pgofs = NULL;
 
        if (f2fs_encrypted_inode(inode))
@@ -672,6 +677,9 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
        bool allocated = false;
        block_t blkaddr;
 
+       if (!maxblocks)
+               return 0;
+
        map->m_len = 0;
        map->m_flags = 0;