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Btrfs: fix double range unlock of hole region when reading page

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If when reading a page we find a hole and our caller had already locked
the range (bio flags has the bit EXTENT_BIO_PARENT_LOCKED set), we end
up unlocking the hole's range and then later our caller unlocks it
again, which might have already been locked by some other task once
the first unlock happened.

Currently this can only happen during a call to the extent_same ioctl,
as it's the only caller of __do_readpage() that sets the bit
EXTENT_BIO_PARENT_LOCKED for bio flags.

Fix this by leaving the unlock exclusively to the caller.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
This commit is contained in:
Filipe Manana 2015-10-13 16:36:09 +01:00
parent 8039d87d9e
commit 5e6ecb362b
1 changed files with 6 additions and 2 deletions
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8
fs/btrfs/extent_io.c
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@ -3070,8 +3070,12 @@ static int __do_readpage(struct extent_io_tree *tree,
set_extent_uptodate(tree, cur, cur + iosize - 1,
&cached, GFP_NOFS);
unlock_extent_cached(tree, cur, cur + iosize - 1,
&cached, GFP_NOFS);
if (parent_locked)
free_extent_state(cached);
else
unlock_extent_cached(tree, cur,
cur + iosize - 1,
&cached, GFP_NOFS);
cur = cur + iosize;
pg_offset += iosize;
continue;