From fa7a56b7fa6b5c3eab8d08e605937b58e03cd1ac Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Thu, 27 Dec 2007 12:28:58 +0000 Subject: [PATCH] tapaio check return value from read() In tools/blktap/drivers/tapaio.c there is a call to read(2) whose return value is not checked. The attached patch attempts to do something vaguely sensible in cases of error. Fully comprehensive error handling in this area would be quite tough to introduce now but at least with this change when things go wrong you stand a chance of getting some information about what happened. Signed-off-by: Ian Jackson --- tools/blktap/drivers/tapaio.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/tools/blktap/drivers/tapaio.c b/tools/blktap/drivers/tapaio.c index ed15436457..a5c8bc74a0 100644 --- a/tools/blktap/drivers/tapaio.c +++ b/tools/blktap/drivers/tapaio.c @@ -30,6 +30,8 @@ #include "tapaio.h" #include "tapdisk.h" #include +#include +#include /** * We used a kernel patch to return an fd associated with the AIO context @@ -149,8 +151,22 @@ tap_aio_get_events(tap_aio_context_t *ctx) if (!ctx->poll_in_thread) nr_events = io_getevents(ctx->aio_ctx, 1, ctx->max_aio_events, ctx->aio_events, NULL); - else - read(ctx->completion_fd[0], &nr_events, sizeof(nr_events)); + else { + int r; + r = read(ctx->completion_fd[0], &nr_events, sizeof(nr_events)); + if (r < 0) { + if (errno == EAGAIN || errno == EINTR) + return 0; + /* This is pretty bad, we'll probably spin */ + DPRINTF("Aargh, read completion_fd failed: %s", + strerror(errno)); + } else if (r != sizeof(nr_events)) { + /* Should never happen because sizeof(nr_events) + * fits in the guaranteed atomic pipe write size. + * Blundering on is slightly nicer than asserting */ + DPRINTF("Aargh, read completion_fd short read %d", r); + } + } return nr_events; } -- 2.30.2