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authorMiao Xie <miaox@cn.fujitsu.com>2013-02-07 05:12:07 -0500
committerJosef Bacik <jbacik@fusionio.com>2013-02-20 12:59:45 -0500
commit0934856d4697e63c14056375e26e3bd6e8ebd34b (patch)
tree5b47949ee3edf90519e901c657b862fa24c1adcc /fs/reiserfs/README
parent4a7d0f6854c4a4ad1dba00a3b128a32d39b9a742 (diff)
Btrfs: fix deadlock due to unsubmitted
The deadlock problem happened when running fsstress(a test program in LTP). Steps to reproduce: # mkfs.btrfs -b 100M <partition> # mount <partition> <mnt> # <Path>/fsstress -p 3 -n 10000000 -d <mnt> The reason is: btrfs_direct_IO() |->do_direct_IO() |->get_page() |->get_blocks() | |->btrfs_delalloc_resereve_space() | |->btrfs_add_ordered_extent() ------- Add a new ordered extent |->dio_send_cur_page(page0) -------------- We didn't submit bio here |->get_page() |->get_blocks() |->btrfs_delalloc_resereve_space() |->flush_space() |->btrfs_start_ordered_extent() |->wait_event() ---------- Wait the completion of the ordered extent that is mentioned above But because we didn't submit the bio that is mentioned above, the ordered extent can not complete, we would wait for its completion forever. There are two methods which can fix this deadlock problem: 1. submit the bio before we invoke get_blocks() 2. reserve the space before we do dio Though the 1st is the simplest way, we need modify the code of VFS, and it is likely to break contiguous requests, and introduce performance regression for the other filesystems. So we have to choose the 2nd way. Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Cc: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
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