From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH v2 18/23] efi_loader: implement a pseudo "file delete"
Date: Thu, 6 Sep 2018 11:43:46 +0900 [thread overview]
Message-ID: <20180906024345.GH18483@linaro.org> (raw)
In-Reply-To: <8176d631-072a-67c9-5792-0aa3d0e0152c@suse.de>
On Wed, Sep 05, 2018 at 10:22:07AM +0200, Alexander Graf wrote:
>
>
> On 05.09.18 04:51, AKASHI Takahiro wrote:
> > On Tue, Sep 04, 2018 at 11:16:38AM +0200, Alexander Graf wrote:
> >>
> >>
> >> On 04.09.18 09:49, AKASHI Takahiro wrote:
> >>> This patch is necessary to run SCT.efi (UEFI Self-Certification Test).
> >>> Returning EFI_SUCCESS can cheat SCT execution.
> >>>
> >>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> >>
> >> How hard would it be to implement a real delete instead?
> >
> > Good question.
> > The hardest part of implementation, I believe, is about handling
> > nasty long file names in a directory, in particular, when
> > directory entries which comprise a single LFN extend across two clusters.
> > In this case, all the entries must be deleted first, and then go back
> > to the first one and modify it. Due to a current simple buffering of
> > cluster (only one cluster buffer a time), some tweak is necessary.
> > In addition, if there is an already-deleted entry ahead of the given file,
> > we need further rewind directory entries and update the "new" last valid
> > one to mark it as so.
> > Those kind of things would make the implementation a bit complicated
> > rather than simple as expected.
> >
> > So unless 'real' delete is a must for anything, I'm lukewarm to
> > work on it.
> >
> > # I admit that we don't have to have this patch just if *delete* returns
> > successfully without doing anything.
>
> I think both truncate-to-zero (this patch) and
> report-success-when-failure (suggested patch) are hacks that shouldn't
> really go upstream that way unfortunately.
>
> The way I read the long file name definitions, I think it should be
> perfectly ok to only remove the short file name directory entry.
Do you accept such an ugly implementation although it yet complies
with fat specification?
> Sure,
> we're leaking a few directory entries for the LFN, but I don't think
> that's too bad. Any fsck should be able to find those later on...
As I said in my cover-letter, fsck would complain any way.
> As for how to delete the entry without rewinding directory entries, you
> can just set name[0]=DELETED_FLAG; to indicate that the SFN is deleted, no?
Yes if DELETED_FLAG=0x5e and if we ignore the specific case where
name[0] be 0x00, which means the entry is the *first* invalid one.
(again, the latter would not be mandatory in term of compatibility.)
Since I have already had the code, "real" delete will be put in my next
version if nobody has concerns on this simple implementation.
Thanks,
-Takahiro AKASHI
>
> Alex
next prev parent reply other threads:[~2018-09-06 2:43 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-04 7:49 [U-Boot] [PATCH v2 00/23] subject: fs: fat: extend FAT write operations AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 01/23] fs: fat: guard the content of include/fat.h AKASHI Takahiro
2018-09-04 8:52 ` Alexander Graf
2018-09-04 10:46 ` Heinrich Schuchardt
2018-09-05 1:54 ` AKASHI Takahiro
2018-09-05 5:53 ` Heinrich Schuchardt
2018-09-05 1:14 ` AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 02/23] fs: fat: extend get_fs_info() for write use AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 03/23] fs: fat: handle "." and ".." of root dir correctly with fat_itr_resolve() AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 04/23] fs: fat: make directory iterator global for write use AKASHI Takahiro
2018-09-04 9:01 ` Alexander Graf
2018-09-04 10:50 ` Heinrich Schuchardt
2018-09-04 10:57 ` Alexander Graf
2018-09-05 2:14 ` AKASHI Takahiro
2018-09-05 8:16 ` Alexander Graf
2018-09-06 2:29 ` AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 05/23] fs: fat: assure iterator's ->dent belongs to ->clust AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 06/23] Revert "fs: fat: cannot write to subdirectories" AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 07/23] fs: fat: check and normailze file name AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 08/23] fs: fat: write returns error code instead of -1 AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 09/23] fs: fat: support write with sub-directory path AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 10/23] fs: fat: refactor write interface for a file offset AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 11/23] fs: fat: support write with non-zero offset AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 12/23] cmd: fat: add offset parameter to fatwrite AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 13/23] fs: add mkdir interface AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 14/23] fs: fat: remember the starting cluster number of directory AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 15/23] fs: fat: support mkdir AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 16/23] cmd: fat: add fatmkdir command AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 17/23] efi_loader: file: support creating a directory AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 18/23] efi_loader: implement a pseudo "file delete" AKASHI Takahiro
2018-09-04 9:16 ` Alexander Graf
2018-09-05 2:51 ` AKASHI Takahiro
2018-09-05 8:22 ` Alexander Graf
2018-09-06 2:43 ` AKASHI Takahiro [this message]
2018-09-06 6:09 ` Alexander Graf
2018-09-04 7:49 ` [U-Boot] [PATCH v2 19/23] fs-test: fix false positive error at Test Case 12 AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 20/23] fs-test: update the test result as of v2018.09 AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 21/23] test/py: convert fs-test.sh to pytest AKASHI Takahiro
2018-09-14 10:54 ` Simon Glass
2018-09-25 4:47 ` AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 22/23] test/py: fs: add extended write operation test AKASHI Takahiro
2018-09-04 7:49 ` [U-Boot] [PATCH v2 23/23] test/py: fs: add fstest/mkdir test AKASHI Takahiro
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