commit c5353126bec17f8c43f2c4ca5b5e55cd6b3ed41c
author Krzysztof Adamski <krzysztof.adamski@sonymobile.com> Wed Jul 16 08:34:30 2014 +0200
committer Johan Redestig <johan.redestig@sonymobile.com> Fri Feb 20 20:56:10 2015 +0000
tree 0e6933e6ae9285caa0e2acc837963b03f75a5d9d
parent 1158c7d5fe7086b42f70a81381558f35b6cd27a9

sdcard: Properly handle deleted nodes

The sdcard fuse deamon is not properly handling deleted nodes that are
still in use (opened by some process). Typically Linux filesystems makes
it possible to open a file, unlink it and then still use it. In case of a
storage emulated by sdcard deamon this does not work as expected - other
process are not able to recreate file/dir with the same name until all
references to deleted file are closed.

The easiest way to trigger this problem is:

process1: mkdir /sdcard/test1; cd /sdcard/test1
process2: rm -r /sdcard/test1
process2: mkdir /sdcard/test1

After that, process2 will get an error:
mkdir failed for /sdcard/test1, Device or resource busy

There is exactly the same problem with files as directories.
This may case issues for example with directories that are
automatically recreated when they are missing (like DCIM directory). If
some process holds file opened inside of such directory but that
directory is removed, process trying to recreate the directory will get
EBUSY error and possibly crash.

Verified on the Z Ultra GPE.

Change-Id: I1cbf0bec135e6aaafba0ce8e5bb594e3639e0007

sdcard/sdcard.c

diff --git a/sdcard/sdcard.c b/sdcard/sdcard.c
index 4d50bf0..7ad14ab 100644
--- a/sdcard/sdcard.c
+++ b/sdcard/sdcard.c
@@ -199,6 +199,8 @@
      * position. Used to support things like OBB. */
     char* graft_path;
     size_t graft_pathlen;
+
+    bool deleted;
 };
 
 static int str_hash(void *key) {
@@ -631,6 +633,8 @@
     node->ino = fuse->inode_ctr++;
     node->gen = fuse->next_generation++;
 
+    node->deleted = false;
+
     derive_permissions_locked(fuse, parent, node);
     acquire_node_locked(node);
     add_node_to_parent_locked(node, parent);
@@ -704,7 +708,7 @@
          * must be considered distinct even if they refer to the same
          * underlying file as otherwise operations such as "mv x x"
          * will not work because the source and target nodes are the same. */
-        if (!strcmp(name, node->name)) {
+        if (!strcmp(name, node->name) && !node->deleted) {
             return node;
         }
     }
@@ -1070,6 +1074,7 @@
 {
     bool has_rw;
     struct node* parent_node;
+    struct node* child_node;
     char parent_path[PATH_MAX];
     char child_path[PATH_MAX];
 
@@ -1091,6 +1096,12 @@
     if (unlink(child_path) < 0) {
         return -errno;
     }
+    pthread_mutex_lock(&fuse->lock);
+    child_node = lookup_child_by_name_locked(parent_node, name);
+    if (child_node) {
+        child_node->deleted = true;
+    }
+    pthread_mutex_unlock(&fuse->lock);
     return 0;
 }
 
@@ -1098,6 +1109,7 @@
         const struct fuse_in_header* hdr, const char* name)
 {
     bool has_rw;
+    struct node* child_node;
     struct node* parent_node;
     char parent_path[PATH_MAX];
     char child_path[PATH_MAX];
@@ -1120,6 +1132,12 @@
     if (rmdir(child_path) < 0) {
         return -errno;
     }
+    pthread_mutex_lock(&fuse->lock);
+    child_node = lookup_child_by_name_locked(parent_node, name);
+    if (child_node) {
+        child_node->deleted = true;
+    }
+    pthread_mutex_unlock(&fuse->lock);
     return 0;
 }