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    ext4: fix deadlock when writing in ENOSPC conditions · 34cf865d
    Jan Kara 提交于
    Akira-san has been reporting rare deadlocks of his machine when running
    xfstests test 269 on ext4 filesystem. The problem turned out to be in
    ext4_da_reserve_metadata() and ext4_da_reserve_space() which called
    ext4_should_retry_alloc() while holding i_data_sem. Since
    ext4_should_retry_alloc() can force a transaction commit, this is a
    lock ordering violation and leads to deadlocks.
    
    Fix the problem by just removing the retry loops. These functions should
    just report ENOSPC to the caller (e.g. ext4_da_write_begin()) and that
    function must take care of retrying after dropping all necessary locks.
    Reported-and-tested-by: NAkira Fujita <a-fujita@rs.jp.nec.com>
    Reviewed-by: NZheng Liu <wenqing.lz@taobao.com>
    Signed-off-by: NJan Kara <jack@suse.cz>
    Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
    Cc: stable@vger.kernel.org
    34cf865d
inode.c 150.1 KB