Re: [f2fs-dev] [PATCH v6] f2fs: support dynamic reserve/release for device aliasing

[Daeho Jeong]

On Tue, Aug 4, 2026 at 6:20 PM Chao Yu <chao@xxxxxxxxxx> wrote:
>
> On 7/30/26 23:46, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@xxxxxxxxxx>
> >
> > This patch adds a dynamic management feature to the existing device
> > aliasing functionality. It allows users to dynamically reserve or
> > release specific devices from the filesystem's free pool at runtime
> > through new ioctls.
> >
> > To support this, three new ioctls are introduced:
> > - F2FS_IOC_RESERVE_DEV_ALIAS: This reclaims the space occupied by a
> >   device aliasing file. It first performs a capacity check, resets GC
> >   victim information for the target range, marks the segments as in-use
> >   to prevent new allocations, and then triggers GC to migrate existing
> >   valid data out of the range. Finally, it reserves these blocks in the
> >   SIT to effectively exclude the device from the usable capacity.
> >
> > - F2FS_IOC_RELEASE_DEV_ALIAS: This releases the reserved space of a
> >   previously reserved device aliasing file. It truncates the blocks
> >   associated with the file, which makes them available for general
> >   filesystem allocation again.
> >
> > - F2FS_IOC_GET_DEV_ALIAS_STATUS: This retrieves the current aliasing
> >   status of a device aliasing file, returning whether the file is
> >   released (inactive alias) or reserved (active alias, with blocks
> >   fully allocated on the device).
> >
> > Signed-off-by: Daeho Jeong <daehojeong@xxxxxxxxxx>
> Reviewed-by: Chao Yu <chao@xxxxxxxxxx>
>
> Thanks,

Oh, I overlooked that ei.blk includes the segment0_blkaddr offset (the
metadata area), so `ei.blk % BLKS_PER_SEC(sbi)` incorrectly checked
alignment from block 0 rather than the segment area start.

I am going to fix it using the `GET_SEGOFF_FROM_SEG0()` macro:
if ((GET_SEGOFF_FROM_SEG0(sbi, ei.blk) % BLKS_PER_SEC(sbi)) ||
(ei.len % BLKS_PER_SEC(sbi))) {
...
}

Thanks,