misc: teach fuse2fs the inusefile command-line option

The inusefile option is useful for scripts that want to know when
fuse2fs is done modifying the file system after it is unmounted.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index ad4795a..bc49edf 100644 (file)
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -212,6 +212,7 @@ struct fuse2fs {
        unsigned long offset;
        unsigned int next_generation;
        unsigned long long cache_size;
+       char *inusefile;
 };
 
 #define FUSE2FS_CHECK_MAGIC(fs, ptr, num) do {if ((ptr)->magic != (num)) \
@@ -4231,6 +4232,7 @@ static struct fuse_opt fuse2fs_opts[] = {
        FUSE_OPT_KEY("noblock_validity", FUSE2FS_IGNORED),
        FUSE_OPT_KEY("nodelalloc",      FUSE2FS_IGNORED),
        FUSE_OPT_KEY("cache_size=%s",   FUSE2FS_CACHE_SIZE),
+       FUSE2FS_OPT("inusefile=%s",     inusefile,              0),
 
        FUSE_OPT_KEY("-V",             FUSE2FS_VERSION),
        FUSE_OPT_KEY("--version",      FUSE2FS_VERSION),
@@ -4283,6 +4285,7 @@ static int fuse2fs_opt_proc(void *data, const char *arg,
        "    -o offset=<bytes>      similar to mount -o offset=<bytes>, mount the partition starting at <bytes>\n"
        "    -o norecovery          don't replay the journal\n"
        "    -o fuse2fs_debug       enable fuse2fs debugging\n"
+       "    -o inusefile=<file>    file to show that fuse is still using the file system image\n"
        "    -o kernel              run this as if it were the kernel, which sets:\n"
        "                           allow_others,default_permissions,suid,dev\n"
        "    -o directio            use O_DIRECT to read and write the disk\n"
@@ -4411,6 +4414,24 @@ int main(int argc, char *argv[])
                fctx.alloc_all_blocks = 1;
        }
 
+       if(fctx.inusefile) {
+               FILE* inusefile=fopen(fctx.inusefile, "w");
+               if(!inusefile) {
+                       fprintf(stderr, "Requested inusefile=%s but couldn't open the file for writing\n", fctx.inusefile);
+                       exit(1);
+               }
+               fclose(inusefile);
+               char* resolved = realpath(fctx.inusefile, NULL);
+               if (!resolved) {
+                       perror("realpath");
+                       fprintf(stderr, "Could not resolve realpath for inusefile=%s\n", fctx.inusefile);
+                       unlink(fctx.inusefile);
+                       exit(1);
+               }
+               free(fctx.inusefile);
+               fctx.inusefile = resolved;
+       }
+
        /* Start up the fs (while we still can use stdout) */
        ret = 2;
        char options[50];
@@ -4615,6 +4636,14 @@ out:
                        com_err(argv[0], err, "while closing fs");
                global_fs = NULL;
        }
+       if(fctx.inusefile) {
+               err = unlink(fctx.inusefile);
+               if (err)
+                       com_err(argv[0], errno, "while unlinking '%s'",
+                               fctx.inusefile);
+       }
+       if (fctx.inusefile)
+               free(fctx.inusefile);
        if (fctx.device)
                free(fctx.device);
        fuse_opt_free_args(&args);