• Kalpak Shah's avatar
    ext4: Expand extra_inodes space per the s_{want,min}_extra_isize fields · 6dd4ee7c
    Kalpak Shah authored
    We need to make sure that existing ext3 filesystems can also avail the
    new fields that have been added to the ext4 inode. We use
    s_want_extra_isize and s_min_extra_isize to decide by how much we should
    expand the inode. If EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE feature is set
    then we expand the inode by max(s_want_extra_isize, s_min_extra_isize ,
    sizeof(ext4_inode) - EXT4_GOOD_OLD_INODE_SIZE) bytes. Actually it is
    still an open question about whether users should be able to set
    s_*_extra_isize smaller than the known fields or not.
    
    This patch also adds the functionality to expand inodes to include the
    newly added fields. We start by trying to expand by s_want_extra_isize
    bytes and if its fails we try to expand by s_min_extra_isize bytes. This
    is done by changing the i_extra_isize if enough space is available in
    the inode and no EAs are present. If EAs are present and there is enough
    space in the inode then the EAs in the inode are shifted to make space.
    If enough space is not available in the inode due to the EAs then 1 or
    more EAs are shifted to the external EA block. In the worst case when
    even the external EA block does not have enough space we inform the user
    that some EA would need to be deleted or s_min_extra_isize would have to
    be reduced.
    Signed-off-by: default avatarAndreas Dilger <adilger@clusterfs.com>
    Signed-off-by: default avatarKalpak Shah <kalpak@clusterfs.com>
    Signed-off-by: default avatarMingming Cao <cmm@us.ibm.com>
    Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
    6dd4ee7c
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