| Message ID | 20110907065621.GL32018@logfs.org |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Sep 7, 2011 at 12:26 PM, Jörn Engel <joern@logfs.org> wrote: > >> Can you suggest what changes have to be done to have >4K writepage size. > > I think the only change strictly necessary is the patch below, > removing an assertion. Plus the second patch below for mklogfs. > Thanks for the patches. I was able to do basic mount-copy-unmount once. Let me test more with multiple mount unmount cycles and see if there are problems. I think we have to give mklogfs /dev/mtdblock0 instead of /dev/mtd0 I updated wikipedia with steps to use logfs http://en.wikipedia.org/wiki/LogFS thanks, mugunthan
On Wed, 7 September 2011 23:00:30 +0530, srimugunthan dhandapani wrote: > > I was able to do basic mount-copy-unmount once. > Let me test more with multiple mount unmount cycles and see if there > are problems. I'm always happy when I can fix bugs. Though not always happy to discover that the d*ckhead who created them was me. > I think we have to give mklogfs /dev/mtdblock0 instead of /dev/mtd0 You can use mtd0 instead of /dev/mtd0, similar to jffs2. Any /dev/foo gets interpreted by some common code in the kernel. As it's not a block device, mount fails. mtd0 doesn't start with /dev/, so it must be special somehow and gets passed to the filesystem. Jffs2 and logfs are can then do something with this string. And yes, this sounds really stupid. Having /dev/mtd0 do the right thing would certainly be less confusing than the current state. > I updated wikipedia with steps to use logfs > http://en.wikipedia.org/wiki/LogFS Cool! Thanks! Jörn
On Thu, Sep 8, 2011 at 12:47 AM, Jörn Engel <joern@logfs.org> wrote:
> You can use mtd0 instead of /dev/mtd0, similar to jffs2.
With logfs, I am a bit confused about when ultimately the data is
written to the flash and in what units it is written as.
The mtd_write() function in dev_mtd.c does writes in units of 4096 bytes.
With Nand flash writepagesize >4K, using "mklogfs mtd0 & mount mtd0" ,
won't logfs pass non-flashpage aligned writes to the nand flash
driver?.
thanks,
mugunthan
difference somewhere between 100x and 1000x. Pretty much whenever you encounter a crap FTL on your random USB stick, SDcard, etc. that is the case. So if you want to avoid caching for your purposes, you'd have to do it in a way that doesn't cause a huge performance regression to these devices. In other words, caching needs to stay in the code, but be made contingent on some condition that I couldn't specify in half an hour. As the result - having both caching and non-caching code, plus some decision heuristic - will be a non-trivial maintenance burden, there should also be a non-trivial performance benefit attached. But then again, I suppose the two patches below mean you won't even attempt going non-caching anyway. :) Jörn -- Unless something dramatically changes, by 2015 we'll be largely wondering what all the fuss surrounding Linux was really about. -- Rob Enderle [PATCH] logfs: remove useless BUG_ON It prevents write sizes >4k. Signed-off-by: Joern Engel <joern@logfs.org> --- fs/logfs/journal.c | 1 - 1 files changed, 0 insertions(+), 1 deletions(-) diff --git a/fs/logfs/journal.c b/fs/logfs/journal.c index 9da2970..1e1c369 100644 --- a/fs/logfs/journal.c +++ b/fs/logfs/journal.c @@ -612,7 +612,6 @@ static size_t __logfs_write_je(struct super_block *sb, void *buf, u16 type, if (len == 0) return logfs_write_header(super, header, 0, type); - BUG_ON(len > sb->s_blocksize); compr_len = logfs_compress(buf, data, len, sb->s_blocksize); if (compr_len < 0 || type == JE_ANCHOR) { memcpy(data, buf, len); -- 1.7.2.3 [PATCH] Allow larger write shift Current flashes with 8k write size already exist. Why pick 16? No good reason, it's a bit bigger and will do for a while. Maybe 32 or 64 would be sane choices - beyond 64 is definitely insane - but until someone can properly argue where exactly the boundary should be, this is good enough for a while. Signed-off-by: Joern Engel <joern@logfs.org> --- mkfs.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/mkfs.c b/mkfs.c index fd54b75..138067a 100644 --- a/mkfs.c +++ b/mkfs.c @@ -514,8 +514,8 @@ static void mkfs(struct super_block *sb) fail("segment shift must be larger than block shift"); if (blockshift != 12) fail("blockshift must be 12"); - if (writeshift > 12) - fail("writeshift too large (max 12)"); + if (writeshift > 16) + fail("writeshift too large (max 16)"); sb->segsize = 1 << segshift; sb->blocksize = 1 << blockshift; sb->blocksize_bits = blockshift;