On Monday, 01 November, 2010, Sage Weil wrote:
> The 'start-sync' command initiates a sync, but does not wait for it to
> complete. A transaction is printed that can be fed to 'wait-sync', which
> will wait for it to commit.
>
> 'wait-sync' can also be used in combination with 'async-snapshot' to wait
> for an async snapshot creation to commit.
>
> Updates the man page too.
>
> Signed-off-by: Sage Weil <sage@xxxxxxxxxxxx>
> ---
> btrfs.c | 9 +++++++++
> btrfs_cmds.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
> btrfs_cmds.h | 2 ++
> man/btrfs.8.in | 14 ++++++++++++++
> 4 files changed, 74 insertions(+), 0 deletions(-)
>
> diff --git a/btrfs.c b/btrfs.c
> index 46314cf..c871f4a 100644
> --- a/btrfs.c
> +++ b/btrfs.c
> @@ -77,6 +77,15 @@ static struct Command commands[] = {
> "filesystem sync", "<path>\n"
> "Force a sync on the filesystem <path>."
> },
> + { do_start_sync, 1,
> + "filesystem start-sync", "<path>\n"
> + "Start a sync on the filesystem <path>, and print the
resulting\n"
> + "transaction id."
> + },
Like the command "btrfs subvol snapshot", I think that it is better to add a
modifier instead of a new command.
btrfs filesystem sync [--async]
Sorry if I noticed this too late. But I don't see a valid reason to add
another command. From a UI point of view the meaning of the command is the
same, change only slight the behavior.
Even tough I have to admint that "sync --async" sound strange. May be flush is
better ?
> + { do_wait_sync, 2,
> + "filesystem wait-sync", "<path> <transid>\n"
> + "Wait for the transaction <transid> on the filesystem at
<path> to commit."
> + },
If I understood correctly this command may be used to wait the execution of
several commands: snapshot, subvolume removal, sync...
I can suggest a more general name like:
# btrfs filesystem wait-transaction <path> <transid>.
(which may be shortened as "btrfs filesystem wait ...").
Another suggestion: instead of checking if the <transid> is 0, leave the
<transid> optional. If <transid> is omitted, then the function waits all the
running transaction.
Finally I suggest to put a little note about the command behvior when a
transaction is started after the command execution: is there a risk of DOS ?
Anyway great work.
Goffredo
> { do_resize, 2,
> "filesystem resize", "[+/-]<newsize>[gkm]|max <filesystem>\n"
> "Resize the file system. If 'max' is passed, the filesystem\n"
> diff --git a/btrfs_cmds.c b/btrfs_cmds.c
> index 8031c58..736437d 100644
> --- a/btrfs_cmds.c
> +++ b/btrfs_cmds.c
> @@ -526,6 +526,55 @@ int do_fssync(int argc, char **argv)
> return 0;
> }
>
> +int do_start_sync(int argc, char **argv)
> +{
> + int fd, res;
> + char *path = argv[1];
> + __u64 transid;
> +
> + fd = open_file_or_dir(path);
> + if (fd < 0) {
> + fprintf(stderr, "ERROR: can't access to '%s'\n", path);
> + return 12;
> + }
> +
> + printf("StartSync '%s'\n", path);
> + res = ioctl(fd, BTRFS_IOC_START_SYNC, &transid);
> + close(fd);
> + if( res < 0 ){
> + fprintf(stderr, "ERROR: unable to fs-syncing '%s'\n", path);
> + return 16;
> + } else {
> + printf("transid %llu\n", (unsigned long long)transid);
> + }
> +
> + return 0;
> +}
> +
> +int do_wait_sync(int argc, char **argv)
> +{
> + int fd, res;
> + char *path = argv[1];
> + __u64 transid = atoll(argv[2]);
> +
> + fd = open_file_or_dir(path);
> + if (fd < 0) {
> + fprintf(stderr, "ERROR: can't access to '%s'\n", path);
> + return 12;
> + }
> +
> + printf("WaitSync '%s' transid %llu\n", path, (unsigned long
long)transid);
> + res = ioctl(fd, BTRFS_IOC_WAIT_SYNC, &transid);
> + close(fd);
> + if( res < 0 ){
> + fprintf(stderr, "ERROR: unable to wait-sync on '%s' transid
%llu: %s\n", path,
> + (unsigned long long)transid, strerror(errno));
> + return 16;
> + }
> +
> + return 0;
> +}
> +
> int do_scan(int argc, char **argv)
> {
> int i, fd;
> diff --git a/btrfs_cmds.h b/btrfs_cmds.h
> index 7bde191..84c489f 100644
> --- a/btrfs_cmds.h
> +++ b/btrfs_cmds.h
> @@ -19,6 +19,8 @@ int do_clone(int nargs, char **argv);
> int do_delete_subvolume(int nargs, char **argv);
> int do_create_subvol(int nargs, char **argv);
> int do_fssync(int nargs, char **argv);
> +int do_start_sync(int nargs, char **argv);
> +int do_wait_sync(int nargs, char **argv);
> int do_defrag(int argc, char **argv);
> int do_show_filesystem(int nargs, char **argv);
> int do_add_volume(int nargs, char **args);
> diff --git a/man/btrfs.8.in b/man/btrfs.8.in
> index 26ef982..e87b5fe 100644
> --- a/man/btrfs.8.in
> +++ b/man/btrfs.8.in
> @@ -19,6 +19,10 @@ btrfs \- control a btrfs filesystem
> .PP
> \fBbtrfs\fP \fBfilesystem sync\fP\fI <path> \fP
> .PP
> +\fBbtrfs\fP \fBfilesystem start-sync\fP\fI <path> \fP
> +.PP
> +\fBbtrfs\fP \fBfilesystem wait-sync\fP\fI <path> <transid>\fP
> +.PP
> \fBbtrfs\fP \fBfilesystem resize\fP\fI [+/\-]<size>[gkm]|max
<filesystem>\fP
> .PP
> \fBbtrfs\fP \fBdevice scan\fP\fI [<device> [<device>..]]\fP
> @@ -115,6 +119,16 @@ all the block devices.
> Force a sync for the filesystem identified by \fI<path>\fR.
> .TP
>
> +\fBfilesystem start-sync\fR\fI <path> \fR
> +Start a sync operation for the filesystem identified by \fI<path>\fR. A
transaction id
> +is printed that can be waited on using the \fBfilesystem wait-sync\fR
command.
> +.TP
> +
> +\fBfilesystem wait-sync\fR\fI <path> <transid>\fR
> +Wait for a the transaction \fI<transid>\fR to commit to disk. If
\fI<transid>\fR is zero,
> +wait for any currently committing transaction to commit.
> +.TP
> +
> .\"
> .\" Some wording are extracted by the resize2fs man page
> .\"
> --
> 1.7.0
>
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