Re: Gentoo with ext4-patch-queue snapshots

[Mingming Cao <cmm@us.ibm.com>]

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On Tue, 2008-07-01 at 17:50 +0000, Gary Hawco wrote:
> Mingming,
> 
> Can you post that patch somewhere for download? I access my email using
> Windows Vista, not in linux, so it would be very laborious to hand copy
> this patch and recreate it in linux.
> 
Patch attached. 

> Updated the 2.6.26-rc8 kernel with the latest snapshot from today at
> 1833hrs GMT. All hell broke loose in Gentoo, The new kernel wouldn't allow
> the system to remount read/write on boot.  But it worked fine in Slackware.
> Gentoo with the experimental openrc-0.2.5 and baselayout2 apparently does
> not like ext4.
> 

The only commit made yesterday was add the 
Add ext4-fix-online-resize-with-mballoc.patch

It does not seem to impact the boot.

Was the filesystem corrupted before you reboot with new kernel? If so
the next reboot will probably refuse to remount it as it need fsck.


> And for clarification, the patch you sent me is not yet in the queue?
> 
Just pushed into the queue today. Please check.

> So to summarize my recent (as of the last seven days of snapshots) saga
> with ext4-queue-patch in Gentoo
> 
> Through 062508/0019hrs no problems (although I do not believe delalloc was
> enabled)
> From 062608/0042 - 062708/2353hrs had segfaulting when copying and tarring
> small files. No other detectable issues.
> From 063008/1704 - 063008/2219hrs --no segfaulting but data corruption in
> one initiation file causing network interfaces to have to be manually
> activated. No data corruption if delalloc disabled
> latest snapshot 070108/1833hrs --system unable to be remounted read/write
> after fsck check.  Manually booted to livecd with e2fsprogs-1.41WIP
> (17-June-2008). Efsck shows no filesystem problems.
> Rolling back to 063008/2219 snapshot fixes boot problems. No segfaulting.
> No data corruption IF delalloc disabled.
> 
> Thanks,
> Gary
> 

[-- Attachment #2: delalloc_i_disksize_update-fix.patch --]
[-- Type: text/x-patch, Size: 2658 bytes --]

Ext4: fix delalloc i_disksize early update issue

From: Mingming Cao <cmm@us.ibm.com>

Ext4_da_write_end() uses ext4_bh_unmapped_or_delay() function to check
if it extend the file size without need for allocation. But at that time
the buffer has not being dirtied yet (done in code later in
block_commit_write()), so it always return true and update i_disksize
(before block allocation). we could fix that ext4_da_write_end() to not
use this helper function.

This also fixed another issue:
The i_disksize is updated at ext4_da_write_end() time if
writes to the end of file, and the buffers are all have
blocks allocated. But if the page had one buffer marked
as buffer_delay, and the write is at EOF and on a buffer has block
already allocated, we certainly need to extend the i_disksize.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
---
 fs/ext4/inode.c |   32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

Index: linux-2.6.26-rc8/fs/ext4/inode.c
===================================================================
--- linux-2.6.26-rc8.orig/fs/ext4/inode.c	2008-07-02 09:53:42.000000000 -0700
+++ linux-2.6.26-rc8/fs/ext4/inode.c	2008-07-02 10:01:09.000000000 -0700
@@ -1891,6 +1891,30 @@ out:
 	return ret;
 }
 
+/*
+ * Check if we should update i_disksize
+ * when write to the end of file but not require block allocation
+ */
+static int ext4_da_should_update_i_disksize(struct page *page,
+					 unsigned long offset)
+{
+	struct buffer_head *head, *bh;
+	unsigned int curr_off = 0;
+
+	head = page_buffers(page);
+	bh = head;
+	do {
+		unsigned int next_off = curr_off + bh->b_size;
+
+		if (curr_off >= offset &&
+		   (!buffer_mapped(bh) || (buffer_delay(bh))))
+			return 0;
+		curr_off = next_off;
+	} while ((bh = bh->b_this_page) != head);
+
+	return 1;
+}
+
 static int ext4_da_write_end(struct file *file,
 				struct address_space *mapping,
 				loff_t pos, unsigned len, unsigned copied,
@@ -1900,6 +1924,10 @@ static int ext4_da_write_end(struct file
 	int ret = 0, ret2;
 	handle_t *handle = ext4_journal_current_handle();
 	loff_t new_i_size;
+	unsigned long start, end;
+
+	start = pos & (PAGE_CACHE_SIZE - 1);
+	end = start + copied;
 
 	/*
 	 * generic_write_end() will run mark_inode_dirty() if i_size
@@ -1909,8 +1937,7 @@ static int ext4_da_write_end(struct file
 
 	new_i_size = pos + copied;
 	if (new_i_size > EXT4_I(inode)->i_disksize)
-		if (!walk_page_buffers(NULL, page_buffers(page),
-				       0, len, NULL, ext4_bh_unmapped_or_delay)){
+		if (ext4_da_should_update_i_disksize(page, end)) {
 			/*
 			 * Updating i_disksize when extending file without
 			 * need block allocation