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mkfs.vfat: fix a problem with over-estimating FAT size

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This commit is contained in:
Denis Vlasenko 2009-03-28 12:17:20 +00:00
parent 70a2c8d531
commit 781b672b37
1 changed files with 15 additions and 6 deletions
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21
util-linux/mkfs_vfat.c
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@ -327,6 +327,7 @@ int mkfs_vfat_main(int argc UNUSED_PARAM, char **argv)
volume_size_bytes >= ((off_t)8)*1024*1024*1024 ? 16 :
volume_size_bytes >= 260*1024*1024 ? 8 : 1;
} else {
// floppy, loop, or regular file
int not_floppy = ioctl(dev, FDGETPRM, &param);
if (not_floppy == 0) {
// floppy disk
@ -367,12 +368,14 @@ int mkfs_vfat_main(int argc UNUSED_PARAM, char **argv)
// Calculate number of clusters, sectors/cluster, sectors/FAT
// (an initial guess for sect_per_clust should already be set)
//
if ((off_t)(volume_size_sect - reserved_sect) < 16) // arbitrary limit
// "mkdosfs -v -F 32 image5k 5" is the minimum:
// 2 sectors for FATs and 2 data sectors
if ((off_t)(volume_size_sect - reserved_sect) < 4)
bb_error_msg_and_die("the image is too small for FAT32");
sect_per_fat = 1;
while (1) {
while (1) {
unsigned spf;
int spf_adj;
off_t tcl = (volume_size_sect - reserved_sect - NUM_FATS * sect_per_fat) / sect_per_clust;
// tcl may be > MAX_CLUST_32 here, but it may be
// because sect_per_fat is underestimated,
@ -382,8 +385,13 @@ int mkfs_vfat_main(int argc UNUSED_PARAM, char **argv)
if (tcl > 0x7fffffff)
goto next;
total_clust = tcl; // fits in uint32_t
spf = ((total_clust + 2) * 4 + bytes_per_sect - 1) / bytes_per_sect;
if (spf <= sect_per_fat) {
spf_adj = ((total_clust + 2) * 4 + bytes_per_sect - 1) / bytes_per_sect - sect_per_fat;
#if 0
bb_error_msg("sect_per_clust:%u sect_per_fat:%u total_clust:%u",
sect_per_clust, sect_per_fat, (int)tcl);
bb_error_msg("adjust to sect_per_fat:%d", spf_adj);
#endif
if (spf_adj <= 0) {
// do not need to adjust sect_per_fat.
// so, was total_clust too big after all?
if (total_clust <= MAX_CLUST_32)
@ -392,7 +400,8 @@ int mkfs_vfat_main(int argc UNUSED_PARAM, char **argv)
goto next;
}
// adjust sect_per_fat, go back and recalc total_clust
sect_per_fat = spf;
// (note: just "sect_per_fat += spf_adj" isn't ok)
sect_per_fat += ((unsigned)spf_adj / 2) | 1;
}
next:
if (sect_per_clust == 128)
@ -409,7 +418,7 @@ int mkfs_vfat_main(int argc UNUSED_PARAM, char **argv)
fprintf(stderr,
"Device '%s':\n"
"heads:%u, sectors/track:%u, bytes/sector:%u\n"
"media descriptor:0x%02x\n"
"media descriptor:%02x\n"
"total sectors:%"OFF_FMT"u, clusters:%u, sectors/cluster:%u\n"
"FATs:2, sectors/FAT:%u\n"
"volumeID:%08x, label:'%s'\n",