On Wed, 15 Jul 2009, Wu Fengguang wrote: > shmem: call set_page_dirty() with locked page > > The dirtying of page and set_page_dirty() can be moved into the page lock. > > - In shmem_write_end(), the page was dirtied while the page lock was held, > but it's being marked dirty just after dropping the page lock. > - In shmem_symlink(), both dirtying and marking can be moved into page lock. > > It's valuable for the hwpoison code to know whether one bad page can be dropped > without losing data. It mainly judges by testing the PG_dirty bit after taking > the page lock. So it becomes important that the dirtying of page and the > marking of dirtiness are both done inside the page lock. Which is a common > practice, but sadly not a rule. > > The noticeable exceptions are > - mapped pages > - pages with buffer_heads > The above pages could go dirty at any time. Fortunately the hwpoison will > unmap the page and release the buffer_heads beforehand anyway. > > Many other types of pages (eg. metadata pages) can also be dirtied at will by > their owners, the hwpoison code cannot do meaningful things to them anyway. > Only the dirtiness of pagecache pages owned by regular files are interested. > > CC: Hugh Dickins <hugh@xxxxxxxxxxx> Ah, those were the days... ;) > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> Acked-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx> > --- > mm/shmem.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > --- linux.orig/mm/shmem.c > +++ linux/mm/shmem.c > @@ -1630,8 +1630,8 @@ shmem_write_end(struct file *file, struc > if (pos + copied > inode->i_size) > i_size_write(inode, pos + copied); > > - unlock_page(page); > set_page_dirty(page); > + unlock_page(page); > page_cache_release(page); > > return copied; > @@ -1968,13 +1968,13 @@ static int shmem_symlink(struct inode *d > iput(inode); > return error; > } > - unlock_page(page); > inode->i_mapping->a_ops = &shmem_aops; > inode->i_op = &shmem_symlink_inode_operations; > kaddr = kmap_atomic(page, KM_USER0); > memcpy(kaddr, symname, len); > kunmap_atomic(kaddr, KM_USER0); > set_page_dirty(page); > + unlock_page(page); > page_cache_release(page); > } > if (dir->i_mode & S_ISGID) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
