UBI: fix deadlock

We cannot call 'ubi_wl_get_peb()' with @ubi->buf_mutex locked,
because 'ubi_wl_get_peb()' may force erasure, which, in turn,
may call 'torture_peb()' which also locks the @ubi->buf_mutex
and deadlocks.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index d8966ba..2e4d6bf 100644 (file)
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -504,12 +504,9 @@ static int recover_peb(struct ubi_device *ubi, int pnum, int vol_id, int lnum,
        if (!vid_hdr)
                return -ENOMEM;
 
-       mutex_lock(&ubi->buf_mutex);
-
 retry:
        new_pnum = ubi_wl_get_peb(ubi, UBI_UNKNOWN);
        if (new_pnum < 0) {
-               mutex_unlock(&ubi->buf_mutex);
                ubi_free_vid_hdr(ubi, vid_hdr);
                return new_pnum;
        }
@@ -529,20 +526,23 @@ retry:
                goto write_error;
 
        data_size = offset + len;
+       mutex_lock(&ubi->buf_mutex);
        memset(ubi->peb_buf1 + offset, 0xFF, len);
 
        /* Read everything before the area where the write failure happened */
        if (offset > 0) {
                err = ubi_io_read_data(ubi, ubi->peb_buf1, pnum, 0, offset);
                if (err && err != UBI_IO_BITFLIPS)
-                       goto out_put;
+                       goto out_unlock;
        }
 
        memcpy(ubi->peb_buf1 + offset, buf, len);
 
        err = ubi_io_write_data(ubi, ubi->peb_buf1, new_pnum, 0, data_size);
-       if (err)
+       if (err) {
+               mutex_unlock(&ubi->buf_mutex);
                goto write_error;
+       }
 
        mutex_unlock(&ubi->buf_mutex);
        ubi_free_vid_hdr(ubi, vid_hdr);
@@ -553,8 +553,9 @@ retry:
        ubi_msg("data was successfully recovered");
        return 0;
 
-out_put:
+out_unlock:
        mutex_unlock(&ubi->buf_mutex);
+out_put:
        ubi_wl_put_peb(ubi, new_pnum, 1);
        ubi_free_vid_hdr(ubi, vid_hdr);
        return err;
@@ -567,7 +568,6 @@ write_error:
        ubi_warn("failed to write to PEB %d", new_pnum);
        ubi_wl_put_peb(ubi, new_pnum, 1);
        if (++tries > UBI_IO_RETRIES) {
-               mutex_unlock(&ubi->buf_mutex);
                ubi_free_vid_hdr(ubi, vid_hdr);
                return err;
        }