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SubjectRe: [f2fs-dev] [PATCH v2] f2fs: add F2FS_IOC_SEC_TRIM_FILE ioctl
2020년 6월 12일 (금) 오전 1:27, Eric Biggers <ebiggers@kernel.org>님이 작성:
>
> On Thu, Jun 11, 2020 at 12:16:52PM +0900, Daeho Jeong wrote:
> > + for (index = pg_start; index < pg_end;) {
> > + struct dnode_of_data dn;
> > + unsigned int end_offset;
> > +
> > + set_new_dnode(&dn, inode, NULL, NULL, 0);
> > + ret = f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE);
> > + if (ret)
> > + goto out;
> > +
> > + end_offset = ADDRS_PER_PAGE(dn.node_page, inode);
> > + if (pg_end < end_offset + index)
> > + end_offset = pg_end - index;
> > +
> > + for (; dn.ofs_in_node < end_offset;
> > + dn.ofs_in_node++, index++) {
> > + struct block_device *cur_bdev;
> > + block_t blkaddr = f2fs_data_blkaddr(&dn);
> > +
> > + if (__is_valid_data_blkaddr(blkaddr)) {
> > + if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode),
> > + blkaddr, DATA_GENERIC_ENHANCE)) {
> > + ret = -EFSCORRUPTED;
> > + goto out;
> > + }
> > + } else
> > + continue;
> > +
> > + cur_bdev = f2fs_target_device(sbi, blkaddr, NULL);
> > + if (f2fs_is_multi_device(sbi)) {
> > + int i = f2fs_target_device_index(sbi, blkaddr);
> > +
> > + blkaddr -= FDEV(i).start_blk;
> > + }
> > +
> > + if (len) {
> > + if (prev_bdev == cur_bdev &&
> > + blkaddr == prev_block + len) {
> > + len++;
> > + } else {
> > + ret = f2fs_secure_erase(prev_bdev,
> > + prev_block, len, flags);
> > + if (ret)
> > + goto out;
> > +
> > + len = 0;
> > + }
> > + }
> > +
> > + if (!len) {
> > + prev_bdev = cur_bdev;
> > + prev_block = blkaddr;
> > + len = 1;
> > + }
> > + }
> > +
> > + f2fs_put_dnode(&dn);
> > + }
>
> This loop processes the entire file, which may be very large. So it could take
> a very long time to execute.
>
> It should at least use the following to make the task killable and preemptible:
>
> if (fatal_signal_pending(current)) {
> err = -EINTR;
> goto out;
> }
> cond_resched();
>

Good point!

> Also, perhaps this ioctl should be made incremental, i.e. take in an
> (offset, length) like pwrite()?
>
> - Eric

Discard and Zeroing will be treated in a unit of block, which is 4KB
in F2FS case.
Do you really need the (offset, length) option here even if the unit
is a 4KB block? I guess this option might make the user even
inconvenienced to use this ioctl, because they have to bear 4KB
alignment in mind.

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