From: "Theodore Y. Ts'o" <email@example.com> To: Eric Sandeen <firstname.lastname@example.org> Cc: Carlos Maiolino <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: Re: Ext4 fiemap implementation Date: Sat, 2 Jun 2018 23:28:53 -0400 [thread overview] Message-ID: <20180603032853.GA3585@thunk.org> (raw) In-Reply-To: <email@example.com> On Fri, Jun 01, 2018 at 10:01:54AM -0500, Eric Sandeen wrote: > > Ted, is there any restriction why ext4_fiemap isn't using iomap_fiemap()? Or any > > reason why ext4 fiemap always returns the offset from the beginning of the > > extent? Would you oppose to have it updated to return the offset initially > > requested? Or maybe, change ext4_fiemap() to use iomap_fiemap()? ext4_fiemap() predates iomap_fiemap(). In fact, it used to be that all of the file systems had their own fiemap() implementation. > > I read the fiemap documentation, but I didn't get a clear understanding if > > fiemap should be returning the beginning of the extent, the offset initially > > requested, or if it depends on FS implementation. > > I think the fiemap docs explicitly state that ext4's behavior is valid: > > > Extents returned mirror > > those on disk - that is, the logical offset of the 1st returned extent > > may start before fm_start, and the range covered by the last returned > > extent may end after fm_length. Actually, I read, "Extents returned mirror those on disk" as meaning that the ext4 behavior is *mandated* by the docs. It would be interesting to see what XFS did before the iomap_fiemap() conversion. Or it could have been that the docs were inconsistent with what XFS was doing and then when when ext4_fiemap() was implemented, we followed the docs. Some software archeology would be required to know for sure. - Ted
next prev parent reply other threads:[~2018-06-03 3:29 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-06-01 12:36 Carlos Maiolino 2018-06-01 15:01 ` Eric Sandeen 2018-06-03 3:28 ` Theodore Y. Ts'o [this message] 2018-06-04 16:43 ` Darrick J. Wong 2018-06-06 13:13 ` Carlos Maiolino 2018-06-06 14:40 ` Darrick J. Wong 2018-06-07 8:31 ` Carlos Maiolino 2018-06-07 16:25 ` Darrick J. Wong 2018-06-08 8:18 ` Carlos Maiolino 2018-06-08 22:41 ` Mark Fasheh 2018-06-11 7:28 ` Carlos Maiolino 2018-06-12 23:52 ` Mark Fasheh 2018-06-13 3:06 ` Theodore Y. Ts'o 2018-06-13 3:32 ` Dave Chinner 2018-06-13 5:04 ` Theodore Y. Ts'o 2018-06-13 7:41 ` Dave Chinner 2018-06-13 12:09 ` Christoph Hellwig 2018-06-14 8:14 ` Carlos Maiolino 2018-06-01 18:57 ` Andreas Dilger
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