tools/virtiofsd/helper.c | 4 ++++ tools/virtiofsd/passthrough_ll.c | 20 ++++++++++++++------ 2 files changed, 18 insertions(+), 6 deletions(-)
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(-)
diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c
index 3105b6c23a..534ff52c64 100644
--- a/tools/virtiofsd/helper.c
+++ b/tools/virtiofsd/helper.c
@@ -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"
);
}
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 94e0de2d2b..1c5ea27821 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -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;
--
2.11.0
On 8/21/20 5:41 AM, Jiachen Zhang wrote:
> 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(-)
>
> diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c
> index 3105b6c23a..534ff52c64 100644
> --- a/tools/virtiofsd/helper.c
> +++ b/tools/virtiofsd/helper.c
> @@ -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"
> );
> }
>
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 94e0de2d2b..1c5ea27821 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -151,6 +151,7 @@ struct lo_data {
> int timeout_set;
> int readdirplus_set;
> int readdirplus_clear;
> + int allow_directio;
Can we use 'allow_direct_io'?
> 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 },
Here too, split 'direct_io'?
> 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;
>
On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > 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(-) Nice, thanks! This will be useful for benchmarking. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > 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(-) > > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > index 3105b6c23a..534ff52c64 100644 > --- a/tools/virtiofsd/helper.c > +++ b/tools/virtiofsd/helper.c > @@ -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" > ); The standard naming convention from existing options is to use $OPTNAME and no_$OPTNAME. IOW, don't use the "allow_" prefix. The options should be just "directio" and "no_directio" Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
On 8/21/20 1:58 PM, Daniel P. Berrangé wrote: > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: >> 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(-) >> >> diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c >> index 3105b6c23a..534ff52c64 100644 >> --- a/tools/virtiofsd/helper.c >> +++ b/tools/virtiofsd/helper.c >> @@ -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" >> ); > > The standard naming convention from existing options is to use > $OPTNAME and no_$OPTNAME. > > IOW, don't use the "allow_" prefix. The options should be just > "directio" and "no_directio" As we have 'max_idle_threads' (and not maxidlethreads), can we use 'direct_io' instead? > > Regards, > Daniel >
On Fri, Aug 21, 2020 at 9:40 PM Philippe Mathieu-Daudé <philmd@redhat.com> wrote: > On 8/21/20 1:58 PM, Daniel P. Berrangé wrote: > > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > >> 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(-) > >> > >> diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > >> index 3105b6c23a..534ff52c64 100644 > >> --- a/tools/virtiofsd/helper.c > >> +++ b/tools/virtiofsd/helper.c > >> @@ -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" > >> ); > > > > The standard naming convention from existing options is to use > > $OPTNAME and no_$OPTNAME. > > > > IOW, don't use the "allow_" prefix. The options should be just > > "directio" and "no_directio" > > As we have 'max_idle_threads' (and not maxidlethreads), can we > use 'direct_io' instead? > > Thanks. I will split them in the next version. Jiachen > > > Regards, > > Daniel > > > >
On Fri, Aug 21, 2020 at 7:58 PM Daniel P. Berrangé <berrange@redhat.com> wrote: > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > > 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(-) > > > > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > > index 3105b6c23a..534ff52c64 100644 > > --- a/tools/virtiofsd/helper.c > > +++ b/tools/virtiofsd/helper.c > > @@ -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" > > ); > > The standard naming convention from existing options is to use > $OPTNAME and no_$OPTNAME. > > IOW, don't use the "allow_" prefix. The options should be just > "directio" and "no_directio" > > Thanks, Daniel. I did consider using "directio" instead of "allow_directio" before I send out this patch. Although "-o directio" makes it consistent with other option names, it may confuse the users of virtiofsd. Because currently, virtiofsd will not add an O_DIRECT to the open flag, it will just retain or discard the O_DIRECT added by guest applications. But "-o direct" may make the users think that virtiofsd will do direct IO all the time. Jiachen > > Regards, > Daniel > -- > |: https://berrange.com -o- > https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- > https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- > https://www.instagram.com/dberrange :| >
On Sat, Aug 22, 2020 at 01:51:04AM +0800, 张佳辰 wrote: > On Fri, Aug 21, 2020 at 7:58 PM Daniel P. Berrangé <berrange@redhat.com> > wrote: > > > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > > > 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(-) > > > > > > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > > > index 3105b6c23a..534ff52c64 100644 > > > --- a/tools/virtiofsd/helper.c > > > +++ b/tools/virtiofsd/helper.c > > > @@ -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" > > > ); > > > > The standard naming convention from existing options is to use > > $OPTNAME and no_$OPTNAME. > > > > IOW, don't use the "allow_" prefix. The options should be just > > "directio" and "no_directio" > > > > Thanks, Daniel. I did consider using "directio" instead of "allow_directio" > before I send out this patch. Although "-o directio" makes it consistent > with other option names, it may confuse the users of virtiofsd. > Because currently, virtiofsd will not add an O_DIRECT to the open flag, > it will just retain or discard the O_DIRECT added by guest applications. > But "-o direct" may make the users think that virtiofsd will do direct IO > all > the time. Then -o allow_direct_io and -o no_allow_direct_io Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
On Mon, Aug 24, 2020 at 5:39 PM Daniel P. Berrangé <berrange@redhat.com> wrote: > On Sat, Aug 22, 2020 at 01:51:04AM +0800, 张佳辰 wrote: > > On Fri, Aug 21, 2020 at 7:58 PM Daniel P. Berrangé <berrange@redhat.com> > > wrote: > > > > > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > > > > 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(-) > > > > > > > > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > > > > index 3105b6c23a..534ff52c64 100644 > > > > --- a/tools/virtiofsd/helper.c > > > > +++ b/tools/virtiofsd/helper.c > > > > @@ -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" > > > > ); > > > > > > The standard naming convention from existing options is to use > > > $OPTNAME and no_$OPTNAME. > > > > > > IOW, don't use the "allow_" prefix. The options should be just > > > "directio" and "no_directio" > > > > > > Thanks, Daniel. I did consider using "directio" instead of > "allow_directio" > > before I send out this patch. Although "-o directio" makes it consistent > > with other option names, it may confuse the users of virtiofsd. > > Because currently, virtiofsd will not add an O_DIRECT to the open flag, > > it will just retain or discard the O_DIRECT added by guest applications. > > But "-o direct" may make the users think that virtiofsd will do direct IO > > all > > the time. > > Then -o allow_direct_io and -o no_allow_direct_io > > OK, thanks. I will use these names in the final version. Jiachen > > Regards, > Daniel > -- > |: https://berrange.com -o- > https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- > https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- > https://www.instagram.com/dberrange :| > >
© 2016 - 2024 Red Hat, Inc.