jffs2: avoid Wempty-body warnings

Building with W=1 shows a few warnings for empty macros:

fs/jffs2/scan.c: In function 'jffs2_scan_xattr_node':
fs/jffs2/scan.c:378:66: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
378 | jffs2_sum_add_xattr_mem(s, rx, ofs - jeb->offset);
| ^
fs/jffs2/scan.c: In function 'jffs2_scan_xref_node':
fs/jffs2/scan.c:434:65: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
434 | jffs2_sum_add_xref_mem(s, rr, ofs - jeb->offset);
| ^
fs/jffs2/scan.c: In function 'jffs2_scan_eraseblock':
fs/jffs2/scan.c:893:88: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
893 | jffs2_sum_add_padding_mem(s, je32_to_cpu(node->totlen));
| ^

Change all these macros to 'do { } while (0)' statements to avoid the
warnings and make the code a little more robust.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

jffs2: Replace zero-length array with flexible-array

There is a regular need in the kernel to provide a way to declare having a
dynamically sized set of trailing elements in a structure. Kernel code should
always use “flexible array members”[1] for these cases. The older style of
one-element or zero-length arrays should no longer be used[2].

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://github.com/KSPP/linux/issues/21

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

[JFFS2] Fix allocation of summary buffer

We can't use vmalloc for the buffer we use for writing summaries,
because some drivers may want to DMA from it. So limit the size to 64KiB
and use kmalloc for it instead.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

[JFFS2] Whitespace cleanups.

Convert many spaces to tabs; one or two other minor cosmetic fixes.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

[JFFS2] Tidy up licensing/copyright boilerplate.

In particular, remove the bit in the LICENCE file about contacting
Red Hat for alternative arrangements. Their errant IS department broke
that arrangement a long time ago -- the policy of collecting copyright
assignments from contributors came to an end when the plug was pulled on
the servers hosting the project, without notice or reason.

We do still dual-license it for use with eCos, with the GPL+exception
licence approved by the FSF as being GPL-compatible. It's just that nobody
has the right to license it differently.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

[JFFS2] Fix dummy jffs2_sum_scan_sumnode() macro for !SUMMARY case.

I added an argument to the real function...

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

[JFFS2] Introduce jffs2_scan_dirty_space() function.

To eliminate the __totlen field from struct jffs2_raw_node_ref, we need
to allocate nodes for dirty space instead of just tweaking the accounting
data. Introduce jffs2_scan_dirty_space() in preparation for that.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

[JFFS2] Optimise reading of eraseblock summary nodes

This improves the time to mount 512MiB of NAND flash on my OLPC prototype
by about 4%. We used to read the last page of the eraseblock twice -- once
to find the offset of the summary node, and again to actually _read_ the
summary node. Now we read the last page only once, and read more only if
we need to.

We also don't allocate a new buffer just for the summary code -- we use
the buffer which was already allocated for the scan. Better still, if the
'buffer' for the scan is actually just a pointer directly into NOR flash,
we use that too, avoiding the memcpy() which we used to do.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

[JFFS2][XATTR] XATTR support on JFFS2 (version. 5)

This attached patches provide xattr support including POSIX-ACL and
SELinux support on JFFS2 (version.5).

There are some significant differences from previous version posted
at last December.
The biggest change is addition of EBS(Erase Block Summary) support.
Currently, both kernel and usermode utility (sumtool) can recognize
xattr nodes which have JFFS2_NODETYPE_XATTR/_XREF nodetype.

In addition, some bugs are fixed.
- A potential race condition was fixed.
- Unexpected fail when updating a xattr by same name/value pair was fixed.
- A bug when removing xattr name/value pair was fixed.

The fundamental structures (such as using two new nodetypes and exclusion
mechanism by rwsem) are unchanged. But most of implementation were reviewed
and updated if necessary.
Espacially, we had to change several internal implementations related to
load_xattr_datum() to avoid a potential race condition.

[1/2] xattr_on_jffs2.kernel.version-5.patch
[2/2] xattr_on_jffs2.utils.version-5.patch

Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

[JFFS2] Rename jffs2_summary_node to jffs2_raw_summary

Signed-off-by: Ferenc Havasi <havasi@inf.u-szeged.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

[JFFS2] Add erase block summary support (mount time improvement)

The goal of summary is to speed up the mount time. Erase block summary (EBS)
stores summary information at the end of every (closed) erase block. It is
no longer necessary to scan all nodes separetly (and read all pages of them)
just read this "small" summary, where every information is stored which is
needed at mount time.

This summary information is stored in a JFFS2_FEATURE_RWCOMPAT_DELETE. During
the mount process if there is no summary info the orignal scan process will
be executed. EBS works with NAND and NOR flashes, too.

There is a user space tool called sumtool to generate this summary
information for a JFFS2 image.

Signed-off-by: Ferenc Havasi <havasi@inf.u-szeged.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>