bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
- xfs_buf_iorequest(bp);
- if (flags & XBF_ASYNC)
+ if (flags & XBF_ASYNC) {
+ xfs_buf_submit(bp);
return 0;
- return xfs_buf_iowait(bp);
+ }
+ return xfs_buf_submit_wait(bp);
}
xfs_buf_t *
bp->b_flags |= XBF_READ;
bp->b_ops = ops;
- if (XFS_FORCED_SHUTDOWN(target->bt_mount)) {
- xfs_buf_relse(bp);
- return NULL;
- }
- xfs_buf_iorequest(bp);
- xfs_buf_iowait(bp);
+ xfs_buf_submit_wait(bp);
return bp;
}
(*(bp->b_iodone))(bp);
else if (bp->b_flags & XBF_ASYNC)
xfs_buf_relse(bp);
- else {
+ else
complete(&bp->b_iowait);
-
- /* release the !XBF_ASYNC ref now we are done. */
- xfs_buf_rele(bp);
- }
}
static void
bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
XBF_WRITE_FAIL | XBF_DONE);
- if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
- trace_xfs_bdstrat_shut(bp, _RET_IP_);
-
- xfs_buf_ioerror(bp, -EIO);
- xfs_buf_stale(bp);
-
- /* sync IO, xfs_buf_ioend is going to remove a ref here */
- xfs_buf_hold(bp);
- xfs_buf_ioend(bp);
- return -EIO;
- }
-
- xfs_buf_iorequest(bp);
-
- error = xfs_buf_iowait(bp);
+ error = xfs_buf_submit_wait(bp);
if (error) {
xfs_force_shutdown(bp->b_target->bt_mount,
SHUTDOWN_META_IO_ERROR);
} else {
/*
* This is guaranteed not to be the last io reference count
- * because the caller (xfs_buf_iorequest) holds a count itself.
+ * because the caller (xfs_buf_submit) holds a count itself.
*/
atomic_dec(&bp->b_io_remaining);
xfs_buf_ioerror(bp, -EIO);
blk_finish_plug(&plug);
}
+/*
+ * Asynchronous IO submission path. This transfers the buffer lock ownership and
+ * the current reference to the IO. It is not safe to reference the buffer after
+ * a call to this function unless the caller holds an additional reference
+ * itself.
+ */
void
-xfs_buf_iorequest(
- xfs_buf_t *bp)
+xfs_buf_submit(
+ struct xfs_buf *bp)
{
- trace_xfs_buf_iorequest(bp, _RET_IP_);
+ trace_xfs_buf_submit(bp, _RET_IP_);
ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
+ ASSERT(bp->b_flags & XBF_ASYNC);
+
+ /* on shutdown we stale and complete the buffer immediately */
+ if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
+ xfs_buf_ioerror(bp, -EIO);
+ bp->b_flags &= ~XBF_DONE;
+ xfs_buf_stale(bp);
+ xfs_buf_ioend(bp);
+ return;
+ }
if (bp->b_flags & XBF_WRITE)
xfs_buf_wait_unpin(bp);
bp->b_io_error = 0;
/*
- * Take references to the buffer. For XBF_ASYNC buffers, holding a
- * reference for as long as submission takes is all that is necessary
- * here. The IO inherits the lock and hold count from the submitter,
- * and these are release during IO completion processing. Taking a hold
- * over submission ensures that the buffer is not freed until we have
- * completed all processing, regardless of when IO errors occur or are
- * reported.
- *
- * However, for synchronous IO, the IO does not inherit the submitters
- * reference count, nor the buffer lock. Hence we need to take an extra
- * reference to the buffer for the for the IO context so that we can
- * guarantee the buffer is not freed until all IO completion processing
- * is done. Otherwise the caller can drop their reference while the IO
- * is still in progress and hence trigger a use-after-free situation.
+ * The caller's reference is released during I/O completion.
+ * This occurs some time after the last b_io_remaining reference is
+ * released, so after we drop our Io reference we have to have some
+ * other reference to ensure the buffer doesn't go away from underneath
+ * us. Take a direct reference to ensure we have safe access to the
+ * buffer until we are finished with it.
*/
xfs_buf_hold(bp);
- if (!(bp->b_flags & XBF_ASYNC))
- xfs_buf_hold(bp);
-
/*
* Set the count to 1 initially, this will stop an I/O completion
_xfs_buf_ioapply(bp);
/*
- * If _xfs_buf_ioapply failed or we are doing synchronous IO that
- * completes extremely quickly, we can get back here with only the IO
- * reference we took above. If we drop it to zero, run completion
- * processing synchronously so that we don't return to the caller with
- * completion still pending. This avoids unnecessary context switches
- * associated with the end_io workqueue.
+ * If _xfs_buf_ioapply failed, we can get back here with only the IO
+ * reference we took above. If we drop it to zero, run completion so
+ * that we don't return to the caller with completion still pending.
*/
if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
- if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
+ if (bp->b_error)
xfs_buf_ioend(bp);
else
xfs_buf_ioend_async(bp);
}
xfs_buf_rele(bp);
+ /* Note: it is not safe to reference bp now we've dropped our ref */
}
/*
- * Waits for I/O to complete on the buffer supplied. It returns immediately if
- * no I/O is pending or there is already a pending error on the buffer, in which
- * case nothing will ever complete. It returns the I/O error code, if any, or
- * 0 if there was no error.
+ * Synchronous buffer IO submission path, read or write.
*/
int
-xfs_buf_iowait(
- xfs_buf_t *bp)
+xfs_buf_submit_wait(
+ struct xfs_buf *bp)
{
- trace_xfs_buf_iowait(bp, _RET_IP_);
+ int error;
- if (!bp->b_error)
- wait_for_completion(&bp->b_iowait);
+ trace_xfs_buf_submit_wait(bp, _RET_IP_);
+
+ ASSERT(!(bp->b_flags & (_XBF_DELWRI_Q | XBF_ASYNC)));
+ if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
+ xfs_buf_ioerror(bp, -EIO);
+ xfs_buf_stale(bp);
+ bp->b_flags &= ~XBF_DONE;
+ return -EIO;
+ }
+
+ if (bp->b_flags & XBF_WRITE)
+ xfs_buf_wait_unpin(bp);
+
+ /* clear the internal error state to avoid spurious errors */
+ bp->b_io_error = 0;
+
+ /*
+ * For synchronous IO, the IO does not inherit the submitters reference
+ * count, nor the buffer lock. Hence we cannot release the reference we
+ * are about to take until we've waited for all IO completion to occur,
+ * including any xfs_buf_ioend_async() work that may be pending.
+ */
+ xfs_buf_hold(bp);
+
+ /*
+ * Set the count to 1 initially, this will stop an I/O completion
+ * callout which happens before we have started all the I/O from calling
+ * xfs_buf_ioend too early.
+ */
+ atomic_set(&bp->b_io_remaining, 1);
+ _xfs_buf_ioapply(bp);
+
+ /*
+ * make sure we run completion synchronously if it raced with us and is
+ * already complete.
+ */
+ if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
+ xfs_buf_ioend(bp);
+
+ /* wait for completion before gathering the error from the buffer */
+ trace_xfs_buf_iowait(bp, _RET_IP_);
+ wait_for_completion(&bp->b_iowait);
trace_xfs_buf_iowait_done(bp, _RET_IP_);
- return bp->b_error;
+ error = bp->b_error;
+
+ /*
+ * all done now, we can release the hold that keeps the buffer
+ * referenced for the entire IO.
+ */
+ xfs_buf_rele(bp);
+ return error;
}
xfs_caddr_t
else
list_del_init(&bp->b_list);
- if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
- trace_xfs_bdstrat_shut(bp, _RET_IP_);
-
- xfs_buf_ioerror(bp, -EIO);
- xfs_buf_stale(bp);
- xfs_buf_ioend(bp);
- continue;
- }
- xfs_buf_iorequest(bp);
+ xfs_buf_submit(bp);
}
blk_finish_plug(&plug);
bp->b_io_length = nbblks;
bp->b_error = 0;
- if (XFS_FORCED_SHUTDOWN(log->l_mp))
- return -EIO;
-
- xfs_buf_iorequest(bp);
- error = xfs_buf_iowait(bp);
- if (error)
+ error = xfs_buf_submit_wait(bp);
+ if (error && !XFS_FORCED_SHUTDOWN(log->l_mp))
xfs_buf_ioerror_alert(bp, __func__);
return error;
}
* We're not going to bother about retrying
* this during recovery. One strike!
*/
- xfs_buf_ioerror_alert(bp, __func__);
- xfs_force_shutdown(bp->b_target->bt_mount,
- SHUTDOWN_META_IO_ERROR);
+ if (!XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
+ xfs_buf_ioerror_alert(bp, __func__);
+ xfs_force_shutdown(bp->b_target->bt_mount,
+ SHUTDOWN_META_IO_ERROR);
+ }
}
bp->b_iodone = NULL;
xfs_buf_ioend(bp);
XFS_BUF_UNASYNC(bp);
bp->b_ops = &xfs_sb_buf_ops;
- if (XFS_FORCED_SHUTDOWN(log->l_mp)) {
- xfs_buf_relse(bp);
- return -EIO;
- }
-
- xfs_buf_iorequest(bp);
- error = xfs_buf_iowait(bp);
+ error = xfs_buf_submit_wait(bp);
if (error) {
- xfs_buf_ioerror_alert(bp, __func__);
- ASSERT(0);
+ if (!XFS_FORCED_SHUTDOWN(log->l_mp)) {
+ xfs_buf_ioerror_alert(bp, __func__);
+ ASSERT(0);
+ }
xfs_buf_relse(bp);
return error;
}
git.samba.org / sfrench / cifs-2.6.git / commitdiff