Re: Possible deadlock with ->writepaged version offlush_dirty_buffers() and 2.4.0
On Wednesday, January 10, 2001 05:56:09 PM -0200 Marcelo Tosatti <[EMAIL PROTECTED]> wrote: > > Hi Chris, > > It seems there is a possible deadlock condition with your patch which > changes flush_dirty_buffers() to use ->writepage (something which we > _definately_ want for 2.5). Take a look: > Yes, good catch. > > mark_buffer_dirty->balance_dirty->wakeup_bdflush->flush_dirty_buffers-> > writepage->block_write_full_page->__block_write_full_page->get_block-> > ext2_get_block->ext2_alloc_branch-> > >ext2_alloc_block->ext2_new_block->lock_super >or >getblk()->lock_super > > > I dont see any reason why this deadlock could'nt happen in practice now. > It won't happen until someone other than fs/buffer.c starts marking ext2 pages dirty. The normal file write path will make sure that any dirty buffers are mapped, so the ext2_get_block code is never run. > If I'm right, it will pretty nasty to fix this. One possible solution is > to _never_ call mark_buffer_dirty() with the superblock lock held (ext2 > has a lot of places likes this right now) > This is probably the best solution, since it is a good idea regardless of my patch. -chris - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/
Re: Possible deadlock with -writepaged version offlush_dirty_buffers() and 2.4.0
On Wednesday, January 10, 2001 05:56:09 PM -0200 Marcelo Tosatti [EMAIL PROTECTED] wrote: Hi Chris, It seems there is a possible deadlock condition with your patch which changes flush_dirty_buffers() to use -writepage (something which we _definately_ want for 2.5). Take a look: Yes, good catch. mark_buffer_dirty-balance_dirty-wakeup_bdflush-flush_dirty_buffers- writepage-block_write_full_page-__block_write_full_page-get_block- ext2_get_block-ext2_alloc_branch- ext2_alloc_block-ext2_new_block-lock_super or getblk()-lock_super I dont see any reason why this deadlock could'nt happen in practice now. It won't happen until someone other than fs/buffer.c starts marking ext2 pages dirty. The normal file write path will make sure that any dirty buffers are mapped, so the ext2_get_block code is never run. If I'm right, it will pretty nasty to fix this. One possible solution is to _never_ call mark_buffer_dirty() with the superblock lock held (ext2 has a lot of places likes this right now) This is probably the best solution, since it is a good idea regardless of my patch. -chris - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/
