fs: fat: assure iterator's ->dent belongs to ->clust

In my attempt to re-work write operation, it was revealed that iterator's
"clust" does not always point to a cluster to which a current directory
entry ("dent") belongs.
This patch assures that it is always true by adding "next_clust" which is
used solely for dereferencing a cluster chain.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index c475f12..8122fef 100644 (file)
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -641,6 +641,7 @@ static int get_fs_info(fsdata *mydata)
 typedef struct {
        fsdata    *fsdata;        /* filesystem parameters */
        unsigned   clust;         /* current cluster */
+       unsigned   next_clust;    /* next cluster if remaining == 0 */
        int        last_cluster;  /* set once we've read last cluster */
        int        is_root;       /* is iterator at root directory */
        int        remaining;     /* remaining dent's in current cluster */
@@ -672,6 +673,7 @@ static int fat_itr_root(fat_itr *itr, fsdata *fsdata)
 
        itr->fsdata = fsdata;
        itr->clust = fsdata->root_cluster;
+       itr->next_clust = fsdata->root_cluster;
        itr->dent = NULL;
        itr->remaining = 0;
        itr->last_cluster = 0;
@@ -707,9 +709,11 @@ static void fat_itr_child(fat_itr *itr, fat_itr *parent)
        itr->fsdata = parent->fsdata;
        if (clustnum > 0) {
                itr->clust = clustnum;
+               itr->next_clust = clustnum;
                itr->is_root = 0;
        } else {
                itr->clust = parent->fsdata->root_cluster;
+               itr->next_clust = parent->fsdata->root_cluster;
                itr->is_root = 1;
        }
        itr->dent = NULL;
@@ -727,7 +731,7 @@ static void *next_cluster(fat_itr *itr)
        if (itr->last_cluster)
                return NULL;
 
-       sect = clust_to_sect(itr->fsdata, itr->clust);
+       sect = clust_to_sect(itr->fsdata, itr->next_clust);
 
        debug("FAT read(sect=%d), clust_size=%d, DIRENTSPERBLOCK=%zd\n",
              sect, itr->fsdata->clust_size, DIRENTSPERBLOCK);
@@ -748,18 +752,19 @@ static void *next_cluster(fat_itr *itr)
                return NULL;
        }
 
+       itr->clust = itr->next_clust;
        if (itr->is_root && itr->fsdata->fatsize != 32) {
-               itr->clust++;
-               sect = clust_to_sect(itr->fsdata, itr->clust);
+               itr->next_clust++;
+               sect = clust_to_sect(itr->fsdata, itr->next_clust);
                if (sect - itr->fsdata->rootdir_sect >=
                    itr->fsdata->rootdir_size) {
-                       debug("cursect: 0x%x\n", itr->clust);
+                       debug("nextclust: 0x%x\n", itr->next_clust);
                        itr->last_cluster = 1;
                }
        } else {
-               itr->clust = get_fatent(itr->fsdata, itr->clust);
-               if (CHECK_CLUST(itr->clust, itr->fsdata->fatsize)) {
-                       debug("cursect: 0x%x\n", itr->clust);
+               itr->next_clust = get_fatent(itr->fsdata, itr->next_clust);
+               if (CHECK_CLUST(itr->next_clust, itr->fsdata->fatsize)) {
+                       debug("nextclust: 0x%x\n", itr->next_clust);
                        itr->last_cluster = 1;
                }
        }
@@ -775,8 +780,11 @@ static dir_entry *next_dent(fat_itr *itr)
                        itr->fsdata->clust_size;
 
                /* have we reached the last cluster? */
-               if (!dent)
+               if (!dent) {
+                       /* a sign for no more entries left */
+                       itr->dent = NULL;
                        return NULL;
+               }
 
                itr->remaining = nbytes / sizeof(dir_entry) - 1;
                itr->dent = dent;
@@ -937,6 +945,7 @@ static int fat_itr_resolve(fat_itr *itr, const char *path, unsigned type)
                    (((next - path) == 2) && !strncmp(path, "..", 2))) {
                        /* point back to itself */
                        itr->clust = itr->fsdata->root_cluster;
+                       itr->next_clust = itr->fsdata->root_cluster;
                        itr->dent = NULL;
                        itr->remaining = 0;
                        itr->last_cluster = 0;