On Tue, 21 Jun 2011, Lukas Czerner wrote:
> On Mon, 20 Jun 2011, Christoph Hellwig wrote:
>
> > Add a new rw_semaphore to protect page_mkwrite against truncate. Previous
> > i_alloc_sem was abused for this, but it's going away in this series.
> >
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> >
> > Index: linux-2.6/fs/ext4/inode.c
> > ===================================================================
> > --- linux-2.6.orig/fs/ext4/inode.c 2011-06-20 14:25:33.779248128 +0200
> > +++ linux-2.6/fs/ext4/inode.c 2011-06-20 14:27:53.025907745 +0200
> > @@ -5357,6 +5357,7 @@ int ext4_setattr(struct dentry *dentry,
> > if (attr->ia_size > sbi->s_bitmap_maxbytes)
> > return -EFBIG;
> > }
> > + down_write(&(EXT4_I(inode)->truncate_lock));
> > }
> >
> > if (S_ISREG(inode->i_mode) &&
> > @@ -5405,6 +5406,9 @@ int ext4_setattr(struct dentry *dentry,
> > ext4_truncate(inode);
> > }
> >
> > + if (attr->ia_valid & ATTR_SIZE)
> > + up_write(&(EXT4_I(inode)->truncate_lock));
> > +
>
> Hi Christoph,
>
> this looks like a bug fix, so we should rather do it in a separate
> commit. Could you send it separately, or at least mention that in commit
> description ?
That's stupid note, it is not a bugfix of course. Ignore it, sorry for
the noise.
>
> Otherwise the patch looks good.
>
> Thanks!
> -Lukas
>
> > if (!rc) {
> > setattr_copy(inode, attr);
> > mark_inode_dirty(inode);
> > @@ -5850,10 +5854,10 @@ int ext4_page_mkwrite(struct vm_area_str
> > struct address_space *mapping = inode->i_mapping;
> >
> > /*
> > - * Get i_alloc_sem to stop truncates messing with the inode. We cannot
> > - * get i_mutex because we are already holding mmap_sem.
> > + * Get truncate_lock to stop truncates messing with the inode. We
> > + * cannot get i_mutex because we are already holding mmap_sem.
> > */
> > - down_read(&inode->i_alloc_sem);
> > + down_read(&(EXT4_I(inode)->truncate_lock));
> > size = i_size_read(inode);
> > if (page->mapping != mapping || size <= page_offset(page)
> > || !PageUptodate(page)) {
> > @@ -5865,7 +5869,7 @@ int ext4_page_mkwrite(struct vm_area_str
> > lock_page(page);
> > wait_on_page_writeback(page);
> > if (PageMappedToDisk(page)) {
> > - up_read(&inode->i_alloc_sem);
> > + up_read(&(EXT4_I(inode)->truncate_lock));
> > return VM_FAULT_LOCKED;
> > }
> >
> > @@ -5883,7 +5887,7 @@ int ext4_page_mkwrite(struct vm_area_str
> > if (page_has_buffers(page)) {
> > if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
> > ext4_bh_unmapped)) {
> > - up_read(&inode->i_alloc_sem);
> > + up_read(&(EXT4_I(inode)->truncate_lock));
> > return VM_FAULT_LOCKED;
> > }
> > }
> > @@ -5912,11 +5916,11 @@ int ext4_page_mkwrite(struct vm_area_str
> > */
> > lock_page(page);
> > wait_on_page_writeback(page);
> > - up_read(&inode->i_alloc_sem);
> > + up_read(&(EXT4_I(inode)->truncate_lock));
> > return VM_FAULT_LOCKED;
> > out_unlock:
> > if (ret)
> > ret = VM_FAULT_SIGBUS;
> > - up_read(&inode->i_alloc_sem);
> > + up_read(&(EXT4_I(inode)->truncate_lock));
> > return ret;
> > }
> > Index: linux-2.6/fs/ext4/super.c
> > ===================================================================
> > --- linux-2.6.orig/fs/ext4/super.c 2011-06-20 14:25:33.795914793 +0200
> > +++ linux-2.6/fs/ext4/super.c 2011-06-20 14:27:06.269243443 +0200
> > @@ -871,6 +871,7 @@ static struct inode *ext4_alloc_inode(st
> > ei->i_datasync_tid = 0;
> > atomic_set(&ei->i_ioend_count, 0);
> > atomic_set(&ei->i_aiodio_unwritten, 0);
> > + init_rwsem(&ei->truncate_lock);
> >
> > return &ei->vfs_inode;
> > }
> > Index: linux-2.6/fs/ext4/ext4.h
> > ===================================================================
> > --- linux-2.6.orig/fs/ext4/ext4.h 2011-06-20 14:25:33.752581461 +0200
> > +++ linux-2.6/fs/ext4/ext4.h 2011-06-20 14:27:06.272576777 +0200
> > @@ -844,6 +844,9 @@ struct ext4_inode_info {
> > /* on-disk additional length */
> > __u16 i_extra_isize;
> >
> > + /* protect page_mkwrite against truncates */
> > + struct rw_semaphore truncate_lock;
> > +
> > #ifdef CONFIG_QUOTA
> > /* quota space reservation, managed internally by quota code */
> > qsize_t i_reserved_quota;
> >
> > --
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> >
>
>
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