• Dave Chinner's avatar
    xfs: avoid nesting transactions in xfs_qm_scall_setqlim() · 08fb3905
    Dave Chinner authored
    Lockdep reports:
    
    =============================================
    [ INFO: possible recursive locking detected ]
    3.9.0+ #3 Not tainted
    ---------------------------------------------
    setquota/28368 is trying to acquire lock:
     (sb_internal){++++.?}, at: [<c11e8846>] xfs_trans_alloc+0x26/0x50
    
    but task is already holding lock:
     (sb_internal){++++.?}, at: [<c11e8846>] xfs_trans_alloc+0x26/0x50
    
    from xfs_qm_scall_setqlim()->xfs_dqread() when a dquot needs to be
    allocated.
    
    xfs_qm_scall_setqlim() is starting a transaction and then not
    passing it into xfs_qm_dqet() and so it starts it's own transaction
    when allocating the dquot.  Splat!
    
    Fix this by not allocating the dquot in xfs_qm_scall_setqlim()
    inside the setqlim transaction. This requires getting the dquot
    first (and allocating it if necessary) then dropping and relocking
    the dquot before joining it to the setqlim transaction.
    Reported-by: default avatarMichael L. Semon <mlsemon35@gmail.com>
    Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
    Reviewed-by: default avatarBen Myers <bpm@sgi.com>
    Signed-off-by: default avatarBen Myers <bpm@sgi.com>
    (cherry picked from commit f648167f)
    08fb3905
xfs_qm_syscalls.c 24.2 KB