@@ -180,6 +180,10 @@ void fuse_cmdline_help(void)
" (0 leaves rlimit unchanged)\n"
" default: min(1000000, fs.file-max - 16384)\n"
" if the current rlimit is lower\n"
+ " -o allow_directio|no_directio\n"
+ " retain/discard O_DIRECT flags passed down\n"
+ " to virtiofsd from guest applications.\n"
+ " default: no_directio\n"
);
}
@@ -151,6 +151,7 @@ struct lo_data {
int timeout_set;
int readdirplus_set;
int readdirplus_clear;
+ int allow_directio;
struct lo_inode root;
GHashTable *inodes; /* protected by lo->mutex */
struct lo_map ino_map; /* protected by lo->mutex */
@@ -179,6 +180,8 @@ static const struct fuse_opt lo_opts[] = {
{ "cache=always", offsetof(struct lo_data, cache), CACHE_ALWAYS },
{ "readdirplus", offsetof(struct lo_data, readdirplus_set), 1 },
{ "no_readdirplus", offsetof(struct lo_data, readdirplus_clear), 1 },
+ { "allow_directio", offsetof(struct lo_data, allow_directio), 1 },
+ { "no_directio", offsetof(struct lo_data, allow_directio), 0 },
FUSE_OPT_END
};
static bool use_syslog = false;
@@ -1516,7 +1519,8 @@ static void lo_releasedir(fuse_req_t req, fuse_ino_t ino,
fuse_reply_err(req, 0);
}
-static void update_open_flags(int writeback, struct fuse_file_info *fi)
+static void update_open_flags(int writeback, int allow_directio,
+ struct fuse_file_info *fi)
{
/*
* With writeback cache, kernel may send read requests even
@@ -1541,10 +1545,13 @@ static void update_open_flags(int writeback, struct fuse_file_info *fi)
/*
* O_DIRECT in guest should not necessarily mean bypassing page
- * cache on host as well. If somebody needs that behavior, it
- * probably should be a configuration knob in daemon.
+ * cache on host as well. Therefore, we discard it by default
+ * ('-o no_directio'). If somebody needs that behavior, the
+ * '-o allow_directio' option should be set.
*/
- fi->flags &= ~O_DIRECT;
+ if (!allow_directio) {
+ fi->flags &= ~O_DIRECT;
+ }
}
static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
@@ -1576,7 +1583,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
goto out;
}
- update_open_flags(lo->writeback, fi);
+ update_open_flags(lo->writeback, lo->allow_directio, fi);
fd = openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOLLOW,
mode);
@@ -1786,7 +1793,7 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=%" PRIu64 ", flags=%d)\n", ino,
fi->flags);
- update_open_flags(lo->writeback, fi);
+ update_open_flags(lo->writeback, lo->allow_directio, fi);
sprintf(buf, "%i", lo_fd(req, ino));
fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
@@ -2824,6 +2831,7 @@ int main(int argc, char *argv[])
.debug = 0,
.writeback = 0,
.posix_lock = 1,
+ .allow_directio = 0,
.proc_self_fd = -1,
};
struct lo_map_elem *root_elem;
Due to the commit 65da4539803373ec4eec97ffc49ee90083e56efd, the O_DIRECT open flag of guest applications will be discarded by virtiofsd. While this behavior makes it consistent with the virtio-9p scheme when guest applications using direct I/O, we no longer have any chance to bypass the host page cache. Therefore, we add a flag 'allow_directio' to lo_data. If '-o no_directio' option is added, or none of '-o no_directio' or '-o allow_directio' is added, the 'allow_directio' will be set to 0, and virtiofsd discards O_DIRECT as before. If '-o allow_directio' is added to the stariting command-line, 'allow_directio' will be set to 1, so that the O_DIRECT flags will be retained and host page cache can be bypassed. Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com> --- tools/virtiofsd/helper.c | 4 ++++ tools/virtiofsd/passthrough_ll.c | 20 ++++++++++++++------ 2 files changed, 18 insertions(+), 6 deletions(-)