cannot build as a module

[PypeBros]

using sources for kernel 3.4.35,
I've got an error about blk_flush_plug_list symbol not being available. It turns out that blk_flush_plug() function used in blkdev.c to implement read-ahead is kernel-internal.

sdfat-flush-plug.patch.txt

[airend]

• Would #ifdef CONFIG_SDFAT_FS_MODULE be better?
• What if we replace blk_start_plug with:

                if (!current->plug)
                        current->plug = &plug;

• That should basically equal blk_flush_plug(current) across all kernels, w/o the extra blk_start_plug overhead.

Still, I wonder why they need to flush just after blk_start_plug; the other drivers don't seem to need it, but maybe it happens in different ways. Also, feel free to comment on #6.

[GrayJack]

Sorry for my ignorance, new into that stuff
What would be the difference using #ifdef CONFIG_SDFAT_FS_MODULE or #ifdef MODULE?

[airend]

What would be the difference using #ifdef CONFIG_SDFAT_FS_MODULE or #ifdef MODULE?

It shouldn't make any difference in this case; just thought the full symbol is more explicit. Either way, maybe we can just use the blk_finish_plug() plus current->plug re-assignment for both cases.