diff options
| -rw-r--r-- | block/file-posix.c | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/block/file-posix.c b/block/file-posix.c index 4de1abd023..c4c06637ef 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -668,6 +668,48 @@ static int hdev_get_max_transfer_length(BlockDriverState *bs, int fd) #endif } +static int hdev_get_max_segments(const struct stat *st) +{ +#ifdef CONFIG_LINUX + char buf[32]; + const char *end; + char *sysfspath; + int ret; + int fd = -1; + long max_segments; + + sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments", + major(st->st_rdev), minor(st->st_rdev)); + fd = open(sysfspath, O_RDONLY); + if (fd == -1) { + ret = -errno; + goto out; + } + do { + ret = read(fd, buf, sizeof(buf)); + } while (ret == -1 && errno == EINTR); + if (ret < 0) { + ret = -errno; + goto out; + } else if (ret == 0) { + ret = -EIO; + goto out; + } + buf[ret] = 0; + /* The file is ended with '\n', pass 'end' to accept that. */ + ret = qemu_strtol(buf, &end, 10, &max_segments); + if (ret == 0 && end && *end == '\n') { + ret = max_segments; + } + +out: + g_free(sysfspath); + return ret; +#else + return -ENOTSUP; +#endif +} + static void raw_refresh_limits(BlockDriverState *bs, Error **errp) { BDRVRawState *s = bs->opaque; @@ -679,6 +721,11 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp) if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) { bs->bl.max_transfer = pow2floor(ret); } + ret = hdev_get_max_segments(&st); + if (ret > 0) { + bs->bl.max_transfer = MIN(bs->bl.max_transfer, + ret * getpagesize()); + } } } |