From: Daniel.E.Messinger@xxxxxxxxxxx
Subject: bidi bsg is non-blocking
Date: Mon, 7 May 2007 10:21:18 -0500
> I'm attempting to use the bidi variant of bsg to talk to an OSD target
> device. I've run into an undesirable situation.
>
> My application has a free-running receive loop (doing a read() on the bsg
> device) waiting for responses to commands sent to bsg by another thread.
> The problem is that the receive thread is getting ENODATA from the read()
> when there are no commands pending. I have NOT set non-blocking.
>
> Note that the old sg driver was quite willing to block until there was a
> response available. I find this scenario greatly preferable.
>
> Could bsg be fixed so that read() blocks when there is nothing to return?
I think that this is a bug.
This patch is against the bsg branch in the Jens' git tree.
I guess that it would be nice to do more cleanups on these parts.
>From 52a9fcf0af72f212ddd93918b7f9f0f0e706c215 Mon Sep 17 00:00:00 2001
From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Date: Tue, 8 May 2007 15:57:43 +0900
Subject: [PATCH] fix read ENODATA bug
This patch fixes a bug that read() gives ENODATA even with a blocking
file descriptor when there are no commands pending.
This also includes some cleanups.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
---
block/bsg.c | 85 ++++++++++++++--------------------------------------------
1 files changed, 21 insertions(+), 64 deletions(-)
diff --git a/block/bsg.c b/block/bsg.c
index a333c93..7fcc77a 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -115,9 +115,9 @@ static void bsg_free_command(struct bsg_
wake_up(&bd->wq_free);
}
-static struct bsg_command *__bsg_alloc_command(struct bsg_device *bd)
+static struct bsg_command *bsg_alloc_command(struct bsg_device *bd)
{
- struct bsg_command *bc = NULL;
+ struct bsg_command *bc = ERR_PTR(-EINVAL);
spin_lock_irq(&bd->lock);
@@ -131,6 +131,7 @@ static struct bsg_command *__bsg_alloc_c
if (unlikely(!bc)) {
spin_lock_irq(&bd->lock);
bd->queued_cmds--;
+ bc = ERR_PTR(-ENOMEM);
goto out;
}
@@ -198,30 +199,6 @@ unlock:
return ret;
}
-/*
- * get a new free command, blocking if needed and specified
- */
-static struct bsg_command *bsg_get_command(struct bsg_device *bd)
-{
- struct bsg_command *bc;
- int ret;
-
- do {
- bc = __bsg_alloc_command(bd);
- if (bc)
- break;
-
- ret = bsg_io_schedule(bd, TASK_INTERRUPTIBLE);
- if (ret) {
- bc = ERR_PTR(ret);
- break;
- }
-
- } while (1);
-
- return bc;
-}
-
static int blk_fill_sgv4_hdr_rq(request_queue_t *q, struct request *rq,
struct sg_io_v4 *hdr, int has_write_perm)
{
@@ -397,7 +374,7 @@ static inline struct bsg_command *bsg_ne
/*
* Get a finished command from the done list
*/
-static struct bsg_command *__bsg_get_done_cmd(struct bsg_device *bd, int state)
+static struct bsg_command *bsg_get_done_cmd(struct bsg_device *bd)
{
struct bsg_command *bc;
int ret;
@@ -407,11 +384,17 @@ static struct bsg_command *__bsg_get_don
if (bc)
break;
- ret = bsg_io_schedule(bd, state);
- if (ret) {
- bc = ERR_PTR(ret);
+ if (!test_bit(BSG_F_BLOCK, &bd->flags)) {
+ bc = ERR_PTR(-EAGAIN);
break;
}
+
+ ret = wait_event_interruptible(bd->wq_done, bd->done_cmds);
+ if (ret) {
+ bc = ERR_PTR(-ERESTARTSYS);
+ break;
+ } else
+ continue;
} while (1);
dprintk("%s: returning done %p\n", bd->name, bc);
@@ -419,18 +402,6 @@ static struct bsg_command *__bsg_get_don
return bc;
}
-static struct bsg_command *
-bsg_get_done_cmd(struct bsg_device *bd, const struct iovec *iov)
-{
- return __bsg_get_done_cmd(bd, TASK_INTERRUPTIBLE);
-}
-
-static struct bsg_command *
-bsg_get_done_cmd_nosignals(struct bsg_device *bd)
-{
- return __bsg_get_done_cmd(bd, TASK_UNINTERRUPTIBLE);
-}
-
static int blk_complete_sgv4_hdr_rq(struct request *rq, struct sg_io_v4 *hdr,
struct bio *bio)
{
@@ -492,22 +463,13 @@ static int bsg_complete_all_commands(str
} while (ret != -ENODATA);
/*
- * discard done commands
+ * discard done commands.
*/
ret = 0;
do {
- bc = bsg_get_done_cmd_nosignals(bd);
-
- /*
- * we _must_ complete before restarting, because
- * bsg_release can't handle this failing.
- */
- if (PTR_ERR(bc) == -ERESTARTSYS)
- continue;
- if (IS_ERR(bc)) {
- ret = PTR_ERR(bc);
+ bc = bsg_get_done_cmd(bd);
+ if (IS_ERR(bc))
break;
- }
tret = blk_complete_sgv4_hdr_rq(bc->rq, &bc->hdr, bc->bio);
if (!ret)
@@ -519,11 +481,9 @@ static int bsg_complete_all_commands(str
return ret;
}
-typedef struct bsg_command *(*bsg_command_callback)(struct bsg_device *bd, const struct iovec *iov);
-
static ssize_t
-__bsg_read(char __user *buf, size_t count, bsg_command_callback get_bc,
- struct bsg_device *bd, const struct iovec *iov, ssize_t *bytes_read)
+__bsg_read(char __user *buf, size_t count, struct bsg_device *bd,
+ const struct iovec *iov, ssize_t *bytes_read)
{
struct bsg_command *bc;
int nr_commands, ret;
@@ -534,7 +494,7 @@ __bsg_read(char __user *buf, size_t coun
ret = 0;
nr_commands = count / sizeof(struct sg_io_v4);
while (nr_commands) {
- bc = get_bc(bd, iov);
+ bc = bsg_get_done_cmd(bd);
if (IS_ERR(bc)) {
ret = PTR_ERR(bc);
break;
@@ -598,8 +558,7 @@ bsg_read(struct file *file, char __user
bsg_set_block(bd, file);
bytes_read = 0;
- ret = __bsg_read(buf, count, bsg_get_done_cmd,
- bd, NULL, &bytes_read);
+ ret = __bsg_read(buf, count, bd, NULL, &bytes_read);
*ppos = bytes_read;
if (!bytes_read || (bytes_read && err_block_err(ret)))
@@ -625,9 +584,7 @@ static ssize_t __bsg_write(struct bsg_de
while (nr_commands) {
request_queue_t *q = bd->queue;
- bc = bsg_get_command(bd);
- if (!bc)
- break;
+ bc = bsg_alloc_command(bd);
if (IS_ERR(bc)) {
ret = PTR_ERR(bc);
bc = NULL;
--
1.4.3.2
-
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