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fs/fat/fat_write: Fix management of empty files 

Overwriting an empty file not created by U-Boot did not work, and it
could even corrupt the FAT. Moreover, creating empty files or emptying
existing files allocated a cluster, which is not standard.

Fix this by always keeping empty files clusterless as specified by
Microsoft (the start cluster must be set to 0 in the directory entry in
that case), and by supporting overwriting such files.

Signed-off-by: Benoît Thébaudeau <benoit@wsystem.com>
This commit is contained in:
Benoît Thébaudeau 2015-09-28 15:45:32 +02:00 committed by Tom Rini
parent e876be4b5c
commit 1254b44a9f
1 changed files with 64 additions and 21 deletions
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85
fs/fat/fat_write.c
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@ -710,6 +710,14 @@ set_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
debug("%llu bytes\n", filesize);
if (!curclust) {
if (filesize) {
debug("error: nonempty clusterless file!\n");
return -1;
}
return 0;
}
actsize = bytesperclust;
endclust = curclust;
do {
@ -765,15 +773,24 @@ getit:
}
/*
* Fill dir_entry
* Set start cluster in directory entry
*/
static void fill_dentry(fsdata *mydata, dir_entry *dentptr,
const char *filename, __u32 start_cluster, __u32 size, __u8 attr)
static void set_start_cluster(const fsdata *mydata, dir_entry *dentptr,
__u32 start_cluster)
{
if (mydata->fatsize == 32)
dentptr->starthi =
cpu_to_le16((start_cluster & 0xffff0000) >> 16);
dentptr->start = cpu_to_le16(start_cluster & 0xffff);
}
/*
* Fill dir_entry
*/
static void fill_dentry(fsdata *mydata, dir_entry *dentptr,
const char *filename, __u32 start_cluster, __u32 size, __u8 attr)
{
set_start_cluster(mydata, dentptr, start_cluster);
dentptr->size = cpu_to_le32(size);
dentptr->attr = attr;
@ -1030,32 +1047,58 @@ static int do_fat_write(const char *filename, void *buffer, loff_t size,
retdent->size = cpu_to_le32(size);
start_cluster = START(retdent);
ret = check_overflow(mydata, start_cluster, size);
if (ret) {
printf("Error: %llu overflow\n", size);
goto exit;
}
if (start_cluster) {
if (size) {
ret = check_overflow(mydata, start_cluster,
size);
if (ret) {
printf("Error: %llu overflow\n", size);
goto exit;
}
}
ret = clear_fatent(mydata, start_cluster);
if (ret) {
printf("Error: clearing FAT entries\n");
goto exit;
ret = clear_fatent(mydata, start_cluster);
if (ret) {
printf("Error: clearing FAT entries\n");
goto exit;
}
if (!size)
set_start_cluster(mydata, retdent, 0);
} else if (size) {
ret = start_cluster = find_empty_cluster(mydata);
if (ret < 0) {
printf("Error: finding empty cluster\n");
goto exit;
}
ret = check_overflow(mydata, start_cluster, size);
if (ret) {
printf("Error: %llu overflow\n", size);
goto exit;
}
set_start_cluster(mydata, retdent, start_cluster);
}
} else {
/* Set short name to set alias checksum field in dir_slot */
set_name(empty_dentptr, filename);
fill_dir_slot(mydata, &empty_dentptr, filename);
ret = start_cluster = find_empty_cluster(mydata);
if (ret < 0) {
printf("Error: finding empty cluster\n");
goto exit;
}
if (size) {
ret = start_cluster = find_empty_cluster(mydata);
if (ret < 0) {
printf("Error: finding empty cluster\n");
goto exit;
}
ret = check_overflow(mydata, start_cluster, size);
if (ret) {
printf("Error: %llu overflow\n", size);
goto exit;
ret = check_overflow(mydata, start_cluster, size);
if (ret) {
printf("Error: %llu overflow\n", size);
goto exit;
}
} else {
start_cluster = 0;
}
/* Set attribute as archieve for regular file */