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On Thu, Jul 03, 2008 at 05:03:25PM +0530, Aneesh Kumar K.V wrote:
> On Wed, Jul 02, 2008 at 10:19:54AM -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.
> >
> > > 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.
> > >
> >
>
> I think we need to protect i_disksize update with i_data_sem. Otherwise
> a parallel writepages and write_end can cause issues. I guess that is
> what Gary is finding. I also did some cleanup for the patch
>
better one moving ext4_truncate i_disksize update under i_data_sem.
ext4_ext_truncate is already doing this.
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index fcaafe4..05e9790 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1893,18 +1893,29 @@ static int ext4_da_write_begin(struct file
*file, struct address_space *mapping,
/*
* Check if we should update i_disksize
* when write to the end of file but not require block allocation
+ * We check only the buffer head mapping the offset.
+ * ex: File with blocksize 1K page size 4K
+ * block 1 and 2 are holes, block 3 is mapped and half filled
+ * seek to block 1 and write ( marked the buffer delay )
+ * seek to block 3 and extent the end of file with end of file still
+ * falling within block 3. Here the writepages won't update the i_disksize
+ * properly because it allocate only block 1. So we need to update
+ * i_disksize in write_end checking only the offset
+ *
*/
-static int ext4_da_should_update_i_disksize(struct page *page,
- unsigned long offset)
+static int ext4_da_should_update_i_disksize(struct address_space *mapping,
+ struct page *page, unsigned long offset)
{
- struct buffer_head *bh;
- unsigned int idx;
int i;
+ unsigned int idx;
+ struct buffer_head *bh;
+ struct inode *inode = mapping->host;
+ unsigned blocksize = inode->i_sb->s_blocksize;
bh = page_buffers(page);
- idx = offset/bh->b_size;
+ idx = (offset + blocksize - 1)/blocksize;
- for (i=0; i < idx; i++)
+ for (i = 1; i < idx; i++)
bh = bh->b_this_page;
if (!buffer_mapped(bh) || (buffer_delay(bh)))
@@ -1934,15 +1945,20 @@ static int ext4_da_write_end(struct file *file,
new_i_size = pos + copied;
if (new_i_size > EXT4_I(inode)->i_disksize)
- if (ext4_da_should_update_i_disksize(page, end)) {
+ if (ext4_da_should_update_i_disksize(mapping, page, end)) {
/*
* Updating i_disksize when extending file without
* need block allocation
*/
- if (ext4_should_order_data(inode))
- ret = ext4_jbd2_file_inode(handle, inode);
+ down_write(&EXT4_I(inode)->i_data_sem);
+ if (new_i_size > EXT4_I(inode)->i_disksize) {
+ if (ext4_should_order_data(inode))
+ ret = ext4_jbd2_file_inode(handle,
+ inode);
- EXT4_I(inode)->i_disksize = new_i_size;
+ EXT4_I(inode)->i_disksize = new_i_size;
+ }
+ up_write(&EXT4_I(inode)->i_data_sem);
}
ret2 = generic_write_end(file, mapping, pos, len, copied,
page, fsdata);
@@ -2987,6 +3003,11 @@ void ext4_truncate(struct inode *inode)
*/
if (ext4_orphan_add(handle, inode))
goto out_stop;
+ /*
+ * From here we block out all ext4_get_block() callers who want to
+ * modify the block allocation tree.
+ */
+ down_write(&ei->i_data_sem);
/*
* The orphan list entry will now protect us from any crash which
@@ -2997,12 +3018,6 @@ void ext4_truncate(struct inode *inode)
*/
ei->i_disksize = inode->i_size;
- /*
- * From here we block out all ext4_get_block() callers who want to
- * modify the block allocation tree.
- */
- down_write(&ei->i_data_sem);
-
if (n == 1) { /* direct blocks */
ext4_free_data(handle, inode, NULL, i_data+offsets[0],
i_data + EXT4_NDIR_BLOCKS);
-aneesh
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