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btrfs: Use ihold instead of igrab in cow_file_range_async 

ihold is supposed to be used when the caller already has a reference to
the inode. In the case of cow_file_range_async this invariants holds,
since the 3 call chains leading to this function all take a reference:

btrfs_writepage  <--- does igrab
 extent_write_full_page
  __extent_writepage
   writepage_delalloc
     btrfs_run_delalloc_range
      cow_file_range_async

extent_write_cache_pages <--- does igrab
 __extent_writepage (same callchain as above)

and

submit_compressed_extents <-- already called from async CoW submit path,
			      which would have done ihold.
 extent_write_locked_range
  __extent_writepage

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Nikolay Borisov 2019-01-03 10:50:01 +02:00 committed by David Sterba
parent 62b3762271
commit bd4691a0e8
1 changed files with 6 additions and 1 deletions
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7
fs/btrfs/inode.c
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@ -1193,7 +1193,12 @@ static int cow_file_range_async(struct inode *inode, struct page *locked_page,
while (start < end) {
async_cow = kmalloc(sizeof(*async_cow), GFP_NOFS);
BUG_ON(!async_cow); /* -ENOMEM */
async_cow->inode = igrab(inode);
/*
* igrab is called higher up in the call chain, take only the
* lightweight reference for the callback lifetime
*/
ihold(inode);
async_cow->inode = inode;
async_cow->fs_info = fs_info;
async_cow->locked_page = locked_page;
async_cow->start = start;