diff options
| -rw-r--r-- | fs/fat/fat.c | 69 |
1 files changed, 51 insertions, 18 deletions
diff --git a/fs/fat/fat.c b/fs/fat/fat.c index 54f42ea..b2a0828 100644 --- a/fs/fat/fat.c +++ b/fs/fat/fat.c @@ -824,8 +824,11 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer, long ret = -1; int firsttime; __u32 root_cluster = 0; + __u32 read_blk; int rootdir_size = 0; - int j; + int buffer_blk_cnt; + int do_read; + __u8 *dir_ptr; if (read_bootsectandvi(&bs, &volinfo, &mydata->fatsize)) { debug("Error: reading boot sector\n"); @@ -910,24 +913,54 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer, isdir = 1; } - j = 0; + buffer_blk_cnt = 0; + firsttime = 1; while (1) { int i; - if (j == 0) { - debug("FAT read sect=%d, clust_size=%d, DIRENTSPERBLOCK=%zd\n", - cursect, mydata->clust_size, DIRENTSPERBLOCK); + if (mydata->fatsize == 32 || firsttime) { + dir_ptr = do_fat_read_at_block; + firsttime = 0; + } else { + /** + * FAT16 sector buffer modification: + * Each loop, the second buffered block is moved to + * the buffer begin, and two next sectors are read + * next to the previously moved one. So the sector + * buffer keeps always 3 sectors for fat16. + * And the current sector is the buffer second sector + * beside the "firsttime" read, when it is the first one. + * + * PREFETCH_BLOCKS is 2 for FAT16 == loop[0:1] + * n = computed root dir sector + * loop | cursect-1 | cursect | cursect+1 | + * 0 | sector n+0 | sector n+1 | none | + * 1 | none | sector n+0 | sector n+1 | + * 0 | sector n+1 | sector n+2 | sector n+3 | + * 1 | sector n+3 | ... + */ + dir_ptr = (do_fat_read_at_block + mydata->sect_size); + memcpy(do_fat_read_at_block, dir_ptr, mydata->sect_size); + } + + do_read = 1; + + if (mydata->fatsize == 32 && buffer_blk_cnt) + do_read = 0; + + if (do_read) { + read_blk = (mydata->fatsize == 32) ? + mydata->clust_size : PREFETCH_BLOCKS; + + debug("FAT read(sect=%d, cnt:%d), clust_size=%d, DIRENTSPERBLOCK=%zd\n", + cursect, read_blk, mydata->clust_size, DIRENTSPERBLOCK); - if (disk_read(cursect, - (mydata->fatsize == 32) ? - (mydata->clust_size) : - PREFETCH_BLOCKS, - do_fat_read_at_block) < 0) { + if (disk_read(cursect, read_blk, dir_ptr) < 0) { debug("Error: reading rootdir block\n"); goto exit; } - dentptr = (dir_entry *) do_fat_read_at_block; + dentptr = (dir_entry *)dir_ptr; } for (i = 0; i < DIRENTSPERBLOCK; i++) { @@ -952,7 +985,7 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer, get_vfatname(mydata, root_cluster, - do_fat_read_at_block, + dir_ptr, dentptr, l_name); if (dols == LS_ROOT) { @@ -1063,7 +1096,7 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer, goto rootdir_done; /* We got a match */ } - debug("END LOOP: j=%d clust_size=%d\n", j, + debug("END LOOP: buffer_blk_cnt=%d clust_size=%d\n", buffer_blk_cnt, mydata->clust_size); /* @@ -1071,10 +1104,10 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer, * root directory clusters when a cluster has been * completely processed. */ - ++j; + ++buffer_blk_cnt; int rootdir_end = 0; if (mydata->fatsize == 32) { - if (j == mydata->clust_size) { + if (buffer_blk_cnt == mydata->clust_size) { int nxtsect = 0; int nxt_clust = 0; @@ -1087,11 +1120,11 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer, root_cluster = nxt_clust; cursect = nxtsect; - j = 0; + buffer_blk_cnt = 0; } } else { - if (j == PREFETCH_BLOCKS) - j = 0; + if (buffer_blk_cnt == PREFETCH_BLOCKS) + buffer_blk_cnt = 0; rootdir_end = (++cursect - mydata->rootdir_sect >= rootdir_size); |