Messages in this thread | | | Date | Sun, 2 Feb 2003 16:00:07 -0800 | From | Andrew Morton <> | Subject | Re: 2.0, 2.2, 2.4, 2.5: fsync buffer race |
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Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> wrote: > > Hi > > there's a race condition in filesystem > > let's have a two inodes that are placed in the same buffer. > > call fsync on inode 1 > it goes down to ext2_update_inode [update == 1] > it calls ll_rw_block at the end > ll_rw_block starts to write buffer > ext2_update_inode waits on buffer > > while the buffer is writing, another process calls fsync on inode 2 > it goes again to ext2_update_inode > it calls ll_rw_block > ll_rw_block sees buffer locked and exits immediatelly > ext2_update_inode waits for buffer > the first write finished, ext2_update_inode exits and changes made by > second proces to inode 2 ARE NOT WRITTEN TO DISK. >
hmm, yes. This is a general weakness in the ll_rw_block() interface. It is not suitable for data-integrity writeouts, as you've pointed out.
A suitable fix would be do create a new
void wait_and_rw_block(...) { wait_on_buffer(bh); ll_rw_block(...); }
and go use that in all the appropriate places.
I shall make that change for 2.5, thanks. - 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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