From 669ced09b3b6070d478acce51810591b78ab0ccd Mon Sep 17 00:00:00 2001 From: Christian Schoenebeck Date: Wed, 22 Sep 2021 15:13:31 +0200 Subject: [PATCH] 9pfs: fix wrong I/O block size in Rgetattr When client sent a 9p Tgetattr request then the wrong I/O block size value was returned by 9p server; instead of host file system's I/O block size it should rather return an I/O block size according to 9p session's 'msize' value, because the value returned to client should be an "optimum" block size for I/O (i.e. to maximize performance), it should not reflect the actual physical block size of the underlying storage media. The I/O block size of a host filesystem is typically 4k, so the value returned was far too low for good 9p I/O performance. This patch adds stat_to_iounit() with a similar approach as the existing get_iounit() function. Signed-off-by: Christian Schoenebeck Reviewed-by: Greg Kurz Message-Id: --- hw/9pfs/9p.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index c857b31321..708b030474 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -1262,6 +1262,25 @@ static int coroutine_fn stat_to_v9stat(V9fsPDU *pdu, V9fsPath *path, #define P9_STATS_ALL 0x00003fffULL /* Mask for All fields above */ +static int32_t stat_to_iounit(const V9fsPDU *pdu, const struct stat *stbuf) +{ + int32_t iounit = 0; + V9fsState *s = pdu->s; + + /* + * iounit should be multiples of st_blksize (host filesystem block size) + * as well as less than (client msize - P9_IOHDRSZ) + */ + if (stbuf->st_blksize) { + iounit = stbuf->st_blksize; + iounit *= (s->msize - P9_IOHDRSZ) / stbuf->st_blksize; + } + if (!iounit) { + iounit = s->msize - P9_IOHDRSZ; + } + return iounit; +} + static int stat_to_v9stat_dotl(V9fsPDU *pdu, const struct stat *stbuf, V9fsStatDotl *v9lstat) { @@ -1273,7 +1292,7 @@ static int stat_to_v9stat_dotl(V9fsPDU *pdu, const struct stat *stbuf, v9lstat->st_gid = stbuf->st_gid; v9lstat->st_rdev = stbuf->st_rdev; v9lstat->st_size = stbuf->st_size; - v9lstat->st_blksize = stbuf->st_blksize; + v9lstat->st_blksize = stat_to_iounit(pdu, stbuf); v9lstat->st_blocks = stbuf->st_blocks; v9lstat->st_atime_sec = stbuf->st_atime; v9lstat->st_atime_nsec = stbuf->st_atim.tv_nsec;