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deploy: Use syncfs() in addition to sync() 

For some sort of crazy reason, the `sync()` system call doesn't
actually return an error code, even though from what I can tell in the
kernel it wouldn't be terribly hard to add.

Regardless though, it is better for userspace apps to use `syncfs()`
to avoid flushing filesystems unrelated to what they want to sync.  In
the case of OSTree, this does matter - for example you might have a
network mount point backing your database, and we don't want to block
upgrades on syncing it.

This change is safe because we're doing syncfs in *addition* to the
previous global `sync()` (a revision from an earlier patch).

Now because OSTree only touches the `/` mount point which covers the
repository, the deployment roots (including their copy of `/etc`), as
well as `/boot`, we should at some point later be able to drop the
`sync()` call.  Note that on initial system installs we do relabel
`/var` but that shouldn't happen at ostree time - any new directories
are taken care of via `systemd-tmpfiles` on boot.
This commit is contained in:
Colin Walters 2015-04-14 13:47:08 -04:00
parent 6d84321a16
commit c58a5c0cb3
1 changed files with 50 additions and 7 deletions
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57
src/libostree/ostree-sysroot-deploy.c
View File

@ -1005,16 +1005,59 @@ checksum_from_kernel_src (GFile *src,
return TRUE;
}
/* FIXME: We should really do individual fdatasync() on files/dirs,
* since this causes us to block on unrelated I/O. However, it's just
* safer for now.
static gboolean
syncfs_dir_at (int dfd,
const char *path,
GCancellable *cancellable,
GError **error)
{
gboolean ret = FALSE;
glnx_fd_close int child_dfd = -1;
if (!glnx_opendirat (dfd, path, TRUE, &child_dfd, error))
goto out;
if (syncfs (child_dfd) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
ret = TRUE;
out:
return ret;
}
/* First, sync the root directory as well as /var and /boot which may
* be separate mount points. Then *in addition*, do a global
* `sync()`.
*/
static gboolean
full_system_sync (GCancellable *cancellable,
full_system_sync (OstreeSysroot *self,
GCancellable *cancellable,
GError **error)
{
gboolean ret = FALSE;
if (syncfs (self->sysroot_fd) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
if (!syncfs_dir_at (self->sysroot_fd, "boot", cancellable, error))
goto out;
/* And now out of an excess of conservativism, we still invoke
* sync(). The advantage of still using `syncfs()` above is that we
* actually get error codes out of that API, and we more clearly
* delineate what we actually want to sync in the future when this
* global sync call is removed.
*/
sync ();
return TRUE;
ret = TRUE;
out:
return ret;
}
static gboolean
@ -1537,7 +1580,7 @@ ostree_sysroot_write_deployments (OstreeSysroot *self,
if (!requires_new_bootversion)
{
if (!full_system_sync (cancellable, error))
if (!full_system_sync (self, cancellable, error))
{
g_prefix_error (error, "Full sync: ");
goto out;
@ -1629,7 +1672,7 @@ ostree_sysroot_write_deployments (OstreeSysroot *self,
}
}
if (!full_system_sync (cancellable, error))
if (!full_system_sync (self, cancellable, error))
{
g_prefix_error (error, "Full sync: ");
goto out;