[v2,05/23] fs: fat: assure iterator's ->dent belongs to ->clust

Message ID 20180904074948.18146-6-takahiro.akashi@linaro.org
State New
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Series
  • subject: fs: fat: extend FAT write operations
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Commit Message

AKASHI Takahiro Sept. 4, 2018, 7:49 a.m.
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>
---
 fs/fat/fat.c  | 24 ++++++++++++++++--------
 include/fat.h |  1 +
 2 files changed, 17 insertions(+), 8 deletions(-)

Patch

diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index 0574af0c0011..1e414380d527 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -653,6 +653,7 @@  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;
@@ -688,9 +689,11 @@  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;
@@ -708,7 +711,7 @@  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);
@@ -729,18 +732,19 @@  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;
 		}
 	}
@@ -756,8 +760,11 @@  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;
@@ -910,6 +917,7 @@  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;
diff --git a/include/fat.h b/include/fat.h
index d86eb5a11576..9b114e3cbda4 100644
--- a/include/fat.h
+++ b/include/fat.h
@@ -200,6 +200,7 @@  static inline u32 sect_to_clust(fsdata *fsdata, int sect)
 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 */