Commit 5e6ecb36 authored Oct 13, 2015 by Filipe Manana

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



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>

parent 8039d87d

fs/btrfs/extent_io.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -3070,7 +3070,11 @@ 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,
		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;

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