From e2b9484ea77119e7a9b720d0f65eedbde23bc5c6 Mon Sep 17 00:00:00 2001
From: Ralph Ronnquist <rrq@rrq.au>
Date: Sat, 12 Aug 2023 08:42:36 +1000
Subject: [PATCH] Added -push action, to push overlay data into source
 fragments.

---
 fusefile.8 | 14 ++++++++---
 fusefile.c | 73 +++++++++++++++++++++++++++++++++++++++++++-----------
 2 files changed, 70 insertions(+), 17 deletions(-)

diff --git a/fusefile.8 b/fusefile.8
index 6af36f4..194f4aa 100644
--- a/fusefile.8
+++ b/fusefile.8
@@ -8,6 +8,8 @@ fusefile, fusedisk \- FUSE file mount for combining file fragments
 .br
 .B fusefile \fB-dump\fR \fR[\fIfuse-opts\fR] \fBmountpoint\fR \fR[\fIoverlay\fR] \fIfilename/from-to\fR ...
 .br
+.B fusefile \fB-push\fR \fR[\fIfuse-opts\fR] \fBmountpoint\fR \fR[\fIoverlay\fR] \fIfilename/from-to\fR ...
+.br
 .B fusedisk \fR[\fIfuse-opts\fR] \fBmountpoint\fR \fR[\fIoverlay\fR] \fIfilename/from-to\fR ...
 
 .SH DESCRIPTION
@@ -33,12 +35,18 @@ from the fragments.
 
 The option \fB-dump\fR as first argument together with a fusefile
 setup will print the setup to standard output rather than establishing
-a fusefile mount. This is of most use with a prior overlay setup,
-where then the printout includes the portions of updates that have
-been captured in the overlay. The printout is the series of fusefile
+a fusefile mount. This is of most use with a prior overlay setup where
+then the printout includes the portions of updates that have been
+captured in the overlay. The printout is the series of fusefile
 fragment argments to give in order to intersperse the captured overlay
 portions according to the overlay table.
 
+The option \fB-push\fR as first argument together with a fusefile
+setup will push the overlay into the sources (except for
+write-protected fragments). This is only of use with a prior overlay
+setup where then the updates that have been captured in the overlay
+get pushed into the fragments.
+
 \fBfusedisk\fR is a helper script to set up a \fBfusefile\fR as a
 block device (via \fIfuseblk\fR) by using the device mapper
 (\fBdmsetup\fR) to manage an empty block device mapping where content
diff --git a/fusefile.c b/fusefile.c
index 9e5cb45..69750fa 100644
--- a/fusefile.c
+++ b/fusefile.c
@@ -717,6 +717,40 @@ static int fusefile_write(const char *path, const char *buf, size_t size,
     return size;
 }
 
+#define PUSHBUF 104857600
+/**
+ * Write data from overlay to source.
+ */
+static void push_oly(off_t beg, off_t end) {
+    static char * buffer = 0;
+    // Pretend that there isn't an overlay
+    char *filename = overlay.source.filename;
+    if ( buffer == 0 ) {
+	buffer = malloc( PUSHBUF );
+	if ( buffer == 0 ) {
+	    fprintf( stderr, "** OOM!!\n" );
+	    exit( 1 );
+	}
+    }
+    overlay.source.filename = 0;
+    while ( beg < end ) {
+	off_t size = end - beg;
+	if ( size > PUSHBUF ) {
+	    size = PUSHBUF;
+	}
+	if ( lseek( overlay.source.fd, beg, SEEK_SET ) < 0 ) {
+	    fprintf( stderr, "** Cannot seek overlay at %ld\n", beg );
+	    break;
+	}
+	size = read( overlay.source.fd, buffer, size );
+	if ( write_block( beg, buffer, size ) < 0 ) {
+	    fprintf( stderr, "** Cannot push %ld bytes at %ld\n", size, beg );
+	}
+	beg += size;
+    }
+    overlay.source.filename = filename;
+}
+
 static void fusefile_destroy(void *data) {
     char *mnt = (char*) data; // As passed to fuse_main
 #if DEBUG
@@ -804,7 +838,7 @@ void *fusefile_init(struct fuse_conn_info *fci) {
 /**
  * Dump the current fragmentation to stdout.
  */
-static int dump_fragments() {
+static int dump_fragments(int push) {
     int oly = 0;
     int src = 0;
     size_t pos = 0;
@@ -814,25 +848,33 @@ static int dump_fragments() {
 	for ( ; src < sources.count && 
 		  ENDSOURCE( sources.array[ src ] ) <= x; src++ ) {
 	    // Dump sources.array[src] in full
-	    fprintf( stdout, "%s/%ld:%ld\n",
-		     sources.array[ src ].filename,
-		     pos - sources.array[ src ].start,
-		     sources.array[ src ].to );
+	    if ( !push ) {
+		fprintf( stdout, "%s/%ld:%ld\n",
+			 sources.array[ src ].filename,
+			 pos - sources.array[ src ].start,
+			 sources.array[ src ].to );
+	    }
 	    pos = ENDSOURCE( sources.array[ src ] );
 	}
 	if ( ( src < sources.count ) && ( sources.array[ src ].start < x ) ) {
 	    // Dump sources.array[src] up to x;
-	    fprintf( stdout, "%s/%ld:%ld\n",
-		     sources.array[ src ].filename,
-		     pos - sources.array[ src ].start,
-		     x - sources.array[ src ].start );
+	    if ( !push ) {
+		fprintf( stdout, "%s/%ld:%ld\n",
+			 sources.array[ src ].filename,
+			 pos - sources.array[ src ].start,
+			 x - sources.array[ src ].start );
+	    }
 	    pos = ENDSOURCE( sources.array[ src ] );
 	}
 	if ( oly < overlay.count ) {
-	    fprintf( stdout, "%s/%ld:%ld\n",
-		     overlay.source.filename,
-		     overlay.table[ oly ].beg,
-		     overlay.table[ oly ].end );
+	    if ( !push ) {
+		fprintf( stdout, "%s/%ld:%ld\n",
+			 overlay.source.filename,
+			 overlay.table[ oly ].beg,
+			 overlay.table[ oly ].end );
+	    } else {
+		push_oly( overlay.table[ oly ].beg, overlay.table[ oly ].end );
+	    }
 	    pos = overlay.table[ oly++ ].end;
 	}
 	for ( ; src < sources.count &&
@@ -975,7 +1017,10 @@ int main(int argc, char *argv[])
     }
     fuseargc = setup_argv( fuseargc, &argv );
     if ( strcmp( "-dump", argv[ 1 ] ) == 0 ) {
-	return dump_fragments();
+	return dump_fragments( 0 );
+    }
+    if ( strcmp( "-push", argv[ 1 ] ) == 0 ) {
+	return dump_fragments( 1 );
     }
     struct fuse_args args = FUSE_ARGS_INIT( fuseargc, argv );
     if ( fuse_parse_cmdline( &args, &mnt, &mt, &fg ) ) {
-- 
2.39.2