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    ext4: journal credits calulation cleanup and fix for non-extent writepage · a02908f1
    Mingming Cao 提交于
    When considering how many journal credits are needed for modifying a
    chunk of data, we need to account for the super block, inode block,
    quota blocks and xattr block, indirect/index blocks, also, group bitmap
    and group descriptor blocks for new allocation (including data and
    indirect/index blocks). There are many places in ext4 do the calculation
    on their own and often missed one or two meta blocks, and often they
    assume single block allocation, and did not considering the multile
    chunk of allocation case.
    
    This patch is trying to cleanup current journal credit code, provides
    some common helper funtion to calculate the journal credits, to be used
    for writepage, writepages, DIO, fallocate, migration, defrag, and for
    both nonextent and extent files.
    
    This patch modified the writepage/write_begin credit caculation for
    nonextent files, to use the new helper function. It also fixed the
    problem that writepage on nonextent files did not consider the case
    blocksize <pagesize, thus could possibelly need multiple block
    allocation in a single transaction.
    Signed-off-by: NMingming Cao <cmm@us.ibm.com>
    Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
    a02908f1
ext4.h 43.5 KB