• Mingming Cao's avatar
    ext2: fix ext2 block reservation early ENOSPC issue · d707d31c
    Mingming Cao authored
    We could run into ENOSPC error on ext2, even when there is free blocks on
    the filesystem.
    
    The problem is triggered in the case the goal block group has 0 free
    blocks , and the rest block groups are skipped due to the check of
    "free_blocks < windowsz/2".  Current code could fall back to non
    reservation allocation to prevent early ENOSPC after examing all the block
    groups with reservation on , but this code was bypassed if the reservation
    window is turned off already, which is true in this case.
    
    This patch fixed two issues:
    1) We don't need to turn off block reservation if the goal block group has
    0 free blocks left and continue search for the rest of block groups.
    
    Current code the intention is to turn off the block reservation if the
    goal allocation group has a few (some) free blocks left (not enough for
    make the desired reservation window),to try to allocation in the goal
    block group, to get better locality.  But if the goal blocks have 0 free
    blocks, it should leave the block reservation on, and continues search for
    the next block groups,rather than turn off block reservation completely.
    
    2) we don't need to check the window size if the block reservation is off.
    
    The problem was originally found and fixed in ext4.
    Signed-off-by: default avatarMingming Cao <cmm@us.ibm.com>
    Cc: Theodore Ts'o <tytso@mit.edu>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    d707d31c
balloc.c 44.6 KB