9a878d1d77
* What This provides an interface for issuing an FITRIM which uses the secure discard instead of just a discard. Only the eMMC command is "secure", and not how the FS uses it: due to the fact that the FS might reassign a region somewhere else, the original deleted data will not be affected by the "trim" which only handles un-used regions. So we'll just call it "deep discard", and note that this is a "best effort" cleanup. * Why Once in a while, We want to be able to cleanup most of the unused blocks after erasing a bunch of files. We don't want to constantly secure-discard via a mount option. From an eMMC spec perspective, it tells the device to really get rid of all the data for the specified blocks and not just put them back into the pool of free ones (unlike the normal TRIM). The eMMC spec says the secure trim handling must make sure the data (and metadata) is not available anymore. A simple TRIM doesn't clear the data, it just puts blocks in the free pool. JEDEC Standard No. 84-A441 7.6.9 Secure Erase 7.6.10 Secure Trim From an FS perspective, it is acceptable to leave some data behind. - directory entries related to deleted files - databases entries related to deleted files - small-file data stored in inode extents - blocks held by the FS waiting to be re-used (mitigated by sync). - blocks reassigned by the FS prior to FIDTRIM. Change-Id: I676a1404a80130d93930c84898360f2e6fb2f81e Signed-off-by: Geremy Condra <gcondra@google.com> Signed-off-by: JP Abgrall <jpa@google.com> |
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| linux | ||
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| Kbuild | ||