bsg: fix a blocking read bug

This patch fixes a bug that read() returns 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@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/bsg.c b/block/bsg.c
index a333c93..2f78d7d 100644 (file)
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -115,9 +115,9 @@ static void bsg_free_command(struct bsg_command *bc)
        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_command(struct bsg_device *bd)
        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_next_done_cmd(struct bsg_device *bd)
 /*
  * 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;
@@ -407,9 +384,14 @@ static struct bsg_command *__bsg_get_done_cmd(struct bsg_device *bd, int state)
                if (bc)
                        break;
 
-               ret = bsg_io_schedule(bd, state);
+               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(ret);
+                       bc = ERR_PTR(-ERESTARTSYS);
                        break;
                }
        } while (1);
@@ -419,18 +401,6 @@ static struct bsg_command *__bsg_get_done_cmd(struct bsg_device *bd, int state)
        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)
 {
@@ -496,19 +466,16 @@ static int bsg_complete_all_commands(struct bsg_device *bd)
         */
        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);
+               spin_lock_irq(&bd->lock);
+               if (!bd->queued_cmds) {
+                       spin_unlock_irq(&bd->lock);
                        break;
                }
 
+               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)
                        ret = tret;
@@ -519,11 +486,9 @@ static int bsg_complete_all_commands(struct bsg_device *bd)
        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 +499,7 @@ __bsg_read(char __user *buf, size_t count, bsg_command_callback get_bc,
        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 +563,7 @@ bsg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 
        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 +589,7 @@ static ssize_t __bsg_write(struct bsg_device *bd, const char __user *buf,
        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;