Hi folks, This patch set has come from the conversion Brian and I have been having over how to fix a use-after-free issue related to IO completions racing with synchronous IO submission. It seemed to me we were having trouble grasping all the different things that were wrong and putting them in a line, so I figured the easiest way to do with was to write a patchset that fixed the original bug, everything else we'd noticed, and changed the IO API such that we wouldn't have problems in the future. So, this patch contains: a) initial fix for the use after free issue (patch 1) b) clear separation of IO submission errors at the XFS level from IO errors reported through BIO completion callbacks (patches 2,3) c) removal of some historic cruft around IO submission (patch 4) d) rework of unnecessarily complex historic error handling paths (patches 5,6,7) e) a new API for clear and concise asynchronous and synchronous IO. (patch 8) The last patch fixes a bug I found writing patch 8, and can probably be moved to first in the series... I was just going to send this compile tested for comments, but I threw it at a couple of VMs and it's half way through xfstests now without any failures. That means I haven't broken anything badly, though the error hendling changes will be interesting to test. The error handling changes have something in common - a buffer that took an IO error was mostly marked stale, but not always. Sometimes they were marked as "not done" indicating that IO needed to be done on them before the contents were valid. Some got marked stale and done, and so on. The thing is, when we mark a buffer stale, it is essentially the same thing as marking it !XBF_DONE. So all the error handling paths now stale the buffer and clear XBF_DONE. Nice, consistent error handling. This enabled some significant cleanups - xfs_trans_buf_read_map() finally got the love it's been needing for long time. It also defines a specific, safe way for waiting on XBF_ASYNC buffer IO, and makes use of that in the buffer delayed write code. Hence the patchset also solves the problem of how do async dispatch, some work, then wait for IO completion as separate steps as opposed to issuing synchronous IO that is waited on immediately. Also, the rework of the IO submission interfaces removes the fixes added in the first patch to solve the use-after-free issue - we no longer need an extra reference to protect parts of the IO completion path because the reference we take during submission is held until after the IO completion wait has occurred. Anyway, I figured patches would speak louder than any description, and most especially a diffstat that looks like this: 9 files changed, 286 insertions(+), 360 deletions(-) Comments welcome. -Dave. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
