diff mbox series

[1/3] xfs_scrub: refactor queueing of subdir scan work item

Message ID 156685447885.2840069.3132139174368034407.stgit@magnolia (mailing list archive)
State Superseded
Headers show
Series xfs_scrub: fix bugs in vfs tree walk code | expand

Commit Message

Darrick J. Wong Aug. 26, 2019, 9:21 p.m. UTC 
From: Darrick J. Wong <darrick.wong@oracle.com>

Replace the open-coded process of queueing a subdirectory for scanning
with a single helper function.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 scrub/vfs.c |   94 +++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 52 insertions(+), 42 deletions(-)

Comments

Dave Chinner Sept. 4, 2019, 8:12 a.m. UTC | #1 
On Mon, Aug 26, 2019 at 02:21:18PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Replace the open-coded process of queueing a subdirectory for scanning
> with a single helper function.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  scrub/vfs.c |   94 +++++++++++++++++++++++++++++++++--------------------------
>  1 file changed, 52 insertions(+), 42 deletions(-)
> 
> 
> diff --git a/scrub/vfs.c b/scrub/vfs.c
> index 7b0b5bcd..ea2866d9 100644
> --- a/scrub/vfs.c
> +++ b/scrub/vfs.c
> @@ -43,6 +43,49 @@ struct scan_fs_tree_dir {
>  	bool			rootdir;
>  };
>  
> +static void scan_fs_dir(struct workqueue *wq, xfs_agnumber_t agno, void *arg);
> +
> +/* Queue a directory for scanning. */
> +static bool
> +queue_subdir(
> +	struct scrub_ctx	*ctx,
> +	struct scan_fs_tree	*sft,
> +	struct workqueue	*wq,
> +	const char		*path,
> +	bool			is_rootdir)
> +{
> +	struct scan_fs_tree_dir	*new_sftd;
> +	int			error;
> +
> +	new_sftd = malloc(sizeof(struct scan_fs_tree_dir));
> +	if (!new_sftd) {
> +		str_errno(ctx, _("creating directory scan context"));
> +		return false;
> +	}
> +
> +	new_sftd->path = strdup(path);
> +	if (!new_sftd->path) {
> +		str_errno(ctx, _("creating directory scan path"));
> +		free(new_sftd);
> +		return false;
> +	}
> +
> +	new_sftd->sft = sft;
> +	new_sftd->rootdir = is_rootdir;
> +
> +	pthread_mutex_lock(&sft->lock);
> +	sft->nr_dirs++;
> +	pthread_mutex_unlock(&sft->lock);
> +	error = workqueue_add(wq, scan_fs_dir, 0, new_sftd);
> +	if (error) {
> +		str_info(ctx, ctx->mntpoint,
> +_("Could not queue subdirectory scan work."));
> +		return false;

Need to drop sft->nr_dirs here, probably free the memory, too.

> @@ -177,41 +203,25 @@ scan_fs_tree(
>  	pthread_mutex_init(&sft.lock, NULL);
>  	pthread_cond_init(&sft.wakeup, NULL);
>  
> -	sftd = malloc(sizeof(struct scan_fs_tree_dir));
> -	if (!sftd) {
> -		str_errno(ctx, ctx->mntpoint);
> -		return false;
> -	}
> -	sftd->path = strdup(ctx->mntpoint);
> -	sftd->sft = &sft;
> -	sftd->rootdir = true;
> -
>  	ret = workqueue_create(&wq, (struct xfs_mount *)ctx,
>  			scrub_nproc_workqueue(ctx));
>  	if (ret) {
>  		str_info(ctx, ctx->mntpoint, _("Could not create workqueue."));
> -		goto out_free;
> +		return false;
>  	}
> -	ret = workqueue_add(&wq, scan_fs_dir, 0, sftd);
> -	if (ret) {
> -		str_info(ctx, ctx->mntpoint,
> -_("Could not queue directory scan work."));
> +
> +	sft.moveon = queue_subdir(ctx, &sft, &wq, ctx->mntpoint, true);
> +	if (!sft.moveon)
>  		goto out_wq;
> -	}

sft is a stack varable that is stuffed into the structure passed to
work run on the workqueue. Is that safe to do here?

>  	pthread_mutex_lock(&sft.lock);
>  	pthread_cond_wait(&sft.wakeup, &sft.lock);

maybe it is because of this, but it's not immediately obvious what
condition actually triggers and that all the work is done...

Cheers,

Dave.
Darrick J. Wong Sept. 4, 2019, 4:37 p.m. UTC | #2 
On Wed, Sep 04, 2019 at 06:12:52PM +1000, Dave Chinner wrote:
> On Mon, Aug 26, 2019 at 02:21:18PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Replace the open-coded process of queueing a subdirectory for scanning
> > with a single helper function.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  scrub/vfs.c |   94 +++++++++++++++++++++++++++++++++--------------------------
> >  1 file changed, 52 insertions(+), 42 deletions(-)
> > 
> > 
> > diff --git a/scrub/vfs.c b/scrub/vfs.c
> > index 7b0b5bcd..ea2866d9 100644
> > --- a/scrub/vfs.c
> > +++ b/scrub/vfs.c
> > @@ -43,6 +43,49 @@ struct scan_fs_tree_dir {
> >  	bool			rootdir;
> >  };
> >  
> > +static void scan_fs_dir(struct workqueue *wq, xfs_agnumber_t agno, void *arg);
> > +
> > +/* Queue a directory for scanning. */
> > +static bool
> > +queue_subdir(
> > +	struct scrub_ctx	*ctx,
> > +	struct scan_fs_tree	*sft,
> > +	struct workqueue	*wq,
> > +	const char		*path,
> > +	bool			is_rootdir)
> > +{
> > +	struct scan_fs_tree_dir	*new_sftd;
> > +	int			error;
> > +
> > +	new_sftd = malloc(sizeof(struct scan_fs_tree_dir));
> > +	if (!new_sftd) {
> > +		str_errno(ctx, _("creating directory scan context"));
> > +		return false;
> > +	}
> > +
> > +	new_sftd->path = strdup(path);
> > +	if (!new_sftd->path) {
> > +		str_errno(ctx, _("creating directory scan path"));
> > +		free(new_sftd);
> > +		return false;
> > +	}
> > +
> > +	new_sftd->sft = sft;
> > +	new_sftd->rootdir = is_rootdir;
> > +
> > +	pthread_mutex_lock(&sft->lock);
> > +	sft->nr_dirs++;
> > +	pthread_mutex_unlock(&sft->lock);
> > +	error = workqueue_add(wq, scan_fs_dir, 0, new_sftd);
> > +	if (error) {
> > +		str_info(ctx, ctx->mntpoint,
> > +_("Could not queue subdirectory scan work."));
> > +		return false;
> 
> Need to drop sft->nr_dirs here, probably free the memory, too.

nr_dirs is (as you've observed) fixed in the next patch.

Yes, we need to free the memory.  Good catch.

> > @@ -177,41 +203,25 @@ scan_fs_tree(
> >  	pthread_mutex_init(&sft.lock, NULL);
> >  	pthread_cond_init(&sft.wakeup, NULL);
> >  
> > -	sftd = malloc(sizeof(struct scan_fs_tree_dir));
> > -	if (!sftd) {
> > -		str_errno(ctx, ctx->mntpoint);
> > -		return false;
> > -	}
> > -	sftd->path = strdup(ctx->mntpoint);
> > -	sftd->sft = &sft;
> > -	sftd->rootdir = true;
> > -
> >  	ret = workqueue_create(&wq, (struct xfs_mount *)ctx,
> >  			scrub_nproc_workqueue(ctx));
> >  	if (ret) {
> >  		str_info(ctx, ctx->mntpoint, _("Could not create workqueue."));
> > -		goto out_free;
> > +		return false;
> >  	}
> > -	ret = workqueue_add(&wq, scan_fs_dir, 0, sftd);
> > -	if (ret) {
> > -		str_info(ctx, ctx->mntpoint,
> > -_("Could not queue directory scan work."));
> > +
> > +	sft.moveon = queue_subdir(ctx, &sft, &wq, ctx->mntpoint, true);
> > +	if (!sft.moveon)
> >  		goto out_wq;
> > -	}
> 
> sft is a stack varable that is stuffed into the structure passed to
> work run on the workqueue. Is that safe to do here?
> 
> >  	pthread_mutex_lock(&sft.lock);
> >  	pthread_cond_wait(&sft.wakeup, &sft.lock);
> 
> maybe it is because of this, but it's not immediately obvious what
> condition actually triggers and that all the work is done...

A worker thread signals the condition variable when nr_dirs hits zero.
There should only be one worker left when this happens (assuming the
accounting is correct) and the worker doesn't do anything with sft after
it unlocks it, so this should be safe.

Will add comment to that effect.

--D

> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com
diff mbox series

Patch

diff --git a/scrub/vfs.c b/scrub/vfs.c
index 7b0b5bcd..ea2866d9 100644
--- a/scrub/vfs.c
+++ b/scrub/vfs.c
@@ -43,6 +43,49 @@  struct scan_fs_tree_dir {
 	bool			rootdir;
 };
 
+static void scan_fs_dir(struct workqueue *wq, xfs_agnumber_t agno, void *arg);
+
+/* Queue a directory for scanning. */
+static bool
+queue_subdir(
+	struct scrub_ctx	*ctx,
+	struct scan_fs_tree	*sft,
+	struct workqueue	*wq,
+	const char		*path,
+	bool			is_rootdir)
+{
+	struct scan_fs_tree_dir	*new_sftd;
+	int			error;
+
+	new_sftd = malloc(sizeof(struct scan_fs_tree_dir));
+	if (!new_sftd) {
+		str_errno(ctx, _("creating directory scan context"));
+		return false;
+	}
+
+	new_sftd->path = strdup(path);
+	if (!new_sftd->path) {
+		str_errno(ctx, _("creating directory scan path"));
+		free(new_sftd);
+		return false;
+	}
+
+	new_sftd->sft = sft;
+	new_sftd->rootdir = is_rootdir;
+
+	pthread_mutex_lock(&sft->lock);
+	sft->nr_dirs++;
+	pthread_mutex_unlock(&sft->lock);
+	error = workqueue_add(wq, scan_fs_dir, 0, new_sftd);
+	if (error) {
+		str_info(ctx, ctx->mntpoint,
+_("Could not queue subdirectory scan work."));
+		return false;
+	}
+
+	return true;
+}
+
 /* Scan a directory sub tree. */
 static void
 scan_fs_dir(
@@ -56,7 +99,6 @@  scan_fs_dir(
 	DIR			*dir;
 	struct dirent		*dirent;
 	char			newpath[PATH_MAX];
-	struct scan_fs_tree_dir	*new_sftd;
 	struct stat		sb;
 	int			dir_fd;
 	int			error;
@@ -117,25 +159,10 @@  scan_fs_dir(
 		/* If directory, call ourselves recursively. */
 		if (S_ISDIR(sb.st_mode) && strcmp(".", dirent->d_name) &&
 		    strcmp("..", dirent->d_name)) {
-			new_sftd = malloc(sizeof(struct scan_fs_tree_dir));
-			if (!new_sftd) {
-				str_errno(ctx, newpath);
-				sft->moveon = false;
-				break;
-			}
-			new_sftd->path = strdup(newpath);
-			new_sftd->sft = sft;
-			new_sftd->rootdir = false;
-			pthread_mutex_lock(&sft->lock);
-			sft->nr_dirs++;
-			pthread_mutex_unlock(&sft->lock);
-			error = workqueue_add(wq, scan_fs_dir, 0, new_sftd);
-			if (error) {
-				str_info(ctx, ctx->mntpoint,
-_("Could not queue subdirectory scan work."));
-				sft->moveon = false;
+			sft->moveon = queue_subdir(ctx, sft, wq, newpath,
+					false);
+			if (!sft->moveon)
 				break;
-			}
 		}
 	}
 
@@ -165,11 +192,10 @@  scan_fs_tree(
 {
 	struct workqueue	wq;
 	struct scan_fs_tree	sft;
-	struct scan_fs_tree_dir	*sftd;
 	int			ret;
 
 	sft.moveon = true;
-	sft.nr_dirs = 1;
+	sft.nr_dirs = 0;
 	sft.root_sb = ctx->mnt_sb;
 	sft.dir_fn = dir_fn;
 	sft.dirent_fn = dirent_fn;
@@ -177,41 +203,25 @@  scan_fs_tree(
 	pthread_mutex_init(&sft.lock, NULL);
 	pthread_cond_init(&sft.wakeup, NULL);
 
-	sftd = malloc(sizeof(struct scan_fs_tree_dir));
-	if (!sftd) {
-		str_errno(ctx, ctx->mntpoint);
-		return false;
-	}
-	sftd->path = strdup(ctx->mntpoint);
-	sftd->sft = &sft;
-	sftd->rootdir = true;
-
 	ret = workqueue_create(&wq, (struct xfs_mount *)ctx,
 			scrub_nproc_workqueue(ctx));
 	if (ret) {
 		str_info(ctx, ctx->mntpoint, _("Could not create workqueue."));
-		goto out_free;
+		return false;
 	}
-	ret = workqueue_add(&wq, scan_fs_dir, 0, sftd);
-	if (ret) {
-		str_info(ctx, ctx->mntpoint,
-_("Could not queue directory scan work."));
+
+	sft.moveon = queue_subdir(ctx, &sft, &wq, ctx->mntpoint, true);
+	if (!sft.moveon)
 		goto out_wq;
-	}
 
 	pthread_mutex_lock(&sft.lock);
 	pthread_cond_wait(&sft.wakeup, &sft.lock);
 	assert(sft.nr_dirs == 0);
 	pthread_mutex_unlock(&sft.lock);
-	workqueue_destroy(&wq);
 
-	return sft.moveon;
 out_wq:
 	workqueue_destroy(&wq);
-out_free:
-	free(sftd->path);
-	free(sftd);
-	return false;
+	return sft.moveon;
 }
 
 #ifndef FITRIM