Messages in this thread | | | Date | Fri, 20 Sep 2002 08:52:01 -0700 | From | Andrew Morton <> | Subject | Re: locking rules for ->dirty_inode() |
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Nikita Danilov wrote: > > Hello, > > Documentation/filesystems/Locking states that all super operations may > block, but __set_page_dirty_buffers() calls > > __mark_inode_dirty()->s_op->dirty_inode() > > under mapping->private_lock spin lock. This seems strange, because file > systems' ->dirty_inode() assume that they are allowed to block. For > example, ext3_dirty_inode() allocates memory in > > ext3_journal_start()->journal_start()->new_handle()->... >
OK, thanks.
mapping->private_lock is taken there to pin page->buffers() (Can't lock the page because set_page_dirty is called under page_table_lock, and other locks).
I'm sure we can just move the spin_unlock up to above the TestSetPageDirty(), but I need to zenuflect for a while over why I did it that way.
It's necessary to expose buffer-dirtiness and page-dirtiness to the rest of the world in the correct order. If we set the page dirty and then the buffers, there is a window in which writeback could find the dirty page, try to write it, discover clean buffers and mark the page clean. We would end up with a !PageDirty page, on mapping->clean_pages, with dirty buffers. It would never be written.
Yup. We can move that spin_unlock up ten lines. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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