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Date: Wed, 02 Jul 2008 13:33:57 -0700
From: Mingming Cao <cmm@...ibm.com>
To: Gary Hawco <ghawco@....net>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Theodore Tso <tytso@....edu>,
"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: Gentoo with ext4-patch-queue snapshots
On Wed, 2008-07-02 at 10:19 -0700, Mingming Cao wrote:
> 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.
Please use this patch instead, after discuss with Ted, I found an issue
with the patch I sent to the list. ext4 patch queue is also updated with
latest patch.
Ext4: fix delalloc i_disksize early update issue
From: Mingming Cao <cmm@...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 in the case blocksize < pagesize, and
if the page has, say, the first buffer marked
as buffer_delay, and the write is to EOF and on the third buffer, which
has block already allocated, we certainly need to extend the i_disksize.
Signed-off-by: Mingming Cao <cmm@...ibm.com>
---
fs/ext4/inode.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 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 13:22:52.000000000 -0700
@@ -1891,6 +1891,32 @@ 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 && offset < next_off)
+ if (!buffer_mapped(bh) || (buffer_delay(bh)))
+ return 0;
+ else
+ return 1;
+ 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 +1926,10 @@ 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 +1939,7 @@ 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
View attachment "delalloc_i_disksize_update-fix.patch" of type "text/x-patch" (2704 bytes)
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