• Tyler Hicks's avatar
    eCryptfs: Revert to a writethrough cache model · 821f7494
    Tyler Hicks authored
    A change was made about a year ago to get eCryptfs to better utilize its
    page cache during writes. The idea was to do the page encryption
    operations during page writeback, rather than doing them when initially
    writing into the page cache, to reduce the number of page encryption
    operations during sequential writes. This meant that the encrypted page
    would only be written to the lower filesystem during page writeback,
    which was a change from how eCryptfs had previously wrote to the lower
    filesystem in ecryptfs_write_end().
    
    The change caused a few eCryptfs-internal bugs that were shook out.
    Unfortunately, more grave side effects have been identified that will
    force changes outside of eCryptfs. Because the lower filesystem isn't
    consulted until page writeback, eCryptfs has no way to pass lower write
    errors (ENOSPC, mainly) back to userspace. Additionaly, it was reported
    that quotas could be bypassed because of the way eCryptfs may sometimes
    open the lower filesystem using a privileged kthread.
    
    It would be nice to resolve the latest issues, but it is best if the
    eCryptfs commits be reverted to the old behavior in the meantime.
    
    This reverts:
    32001d6f "eCryptfs: Flush file in vma close"
    5be79de2 "eCryptfs: Flush dirty pages in setattr"
    57db4e8d "ecryptfs: modify write path to encrypt page in writepage"
    Signed-off-by: default avatarTyler Hicks <tyhicks@canonical.com>
    Tested-by: default avatarColin King <colin.king@canonical.com>
    Cc: Colin King <colin.king@canonical.com>
    Cc: Thieu Le <thieule@google.com>
    821f7494
mmap.c 15.8 KB