[U-Boot] [PATCH 3/7] FAT: Fix redundant sector read

With the previous code, the remaining prefetched sectors were read again after each sector. With this patch, each sector is read only once, thus making the prefetch useful.
Signed-off-by: Benoît Thébaudeau benoit.thebaudeau@advansee.com Cc: Wolfgang Denk wd@denx.de --- .../fs/fat/fat.c | 59 +++++++++++--------- 1 file changed, 33 insertions(+), 26 deletions(-)
diff --git u-boot-66714b1.orig/fs/fat/fat.c u-boot-66714b1/fs/fat/fat.c index e628cf7..fcce412 100644 --- u-boot-66714b1.orig/fs/fat/fat.c +++ u-boot-66714b1/fs/fat/fat.c @@ -777,7 +777,7 @@ do_fat_read (const char *filename, void *buffer, unsigned long maxsize, volume_info volinfo; fsdata datablock; fsdata *mydata = &datablock; - dir_entry *dentptr; + dir_entry *dentptr = NULL; __u16 prevcksum = 0xffff; char *subname = ""; __u32 cursect; @@ -876,19 +876,21 @@ do_fat_read (const char *filename, void *buffer, unsigned long maxsize, while (1) { int i;
- debug("FAT read sect=%d, clust_size=%d, DIRENTSPERBLOCK=%zd\n", - cursect, mydata->clust_size, DIRENTSPERBLOCK); + if (j == 0) { + debug("FAT read sect=%d, clust_size=%d, DIRENTSPERBLOCK=%zd\n", + cursect, mydata->clust_size, DIRENTSPERBLOCK);
- if (disk_read(cursect, - (mydata->fatsize == 32) ? - (mydata->clust_size) : - PREFETCH_BLOCKS, - do_fat_read_block) < 0) { - debug("Error: reading rootdir block\n"); - goto exit; - } + if (disk_read(cursect, + (mydata->fatsize == 32) ? + (mydata->clust_size) : + PREFETCH_BLOCKS, + do_fat_read_block) < 0) { + debug("Error: reading rootdir block\n"); + goto exit; + }
- dentptr = (dir_entry *) do_fat_read_block; + dentptr = (dir_entry *) do_fat_read_block; + }
for (i = 0; i < DIRENTSPERBLOCK; i++) { char s_name[14], l_name[VFAT_MAXLEN_BYTES]; @@ -1030,28 +1032,33 @@ do_fat_read (const char *filename, void *buffer, unsigned long maxsize, * completely processed. */ ++j; - int fat32_end = 0; - if ((mydata->fatsize == 32) && (j == mydata->clust_size)) { - int nxtsect = 0; - int nxt_clust = 0; + int rootdir_end = 0; + if (mydata->fatsize == 32) { + if (j == mydata->clust_size) { + int nxtsect = 0; + int nxt_clust = 0;
- nxt_clust = get_fatent(mydata, root_cluster); - fat32_end = CHECK_CLUST(nxt_clust, 32); + nxt_clust = get_fatent(mydata, root_cluster); + rootdir_end = CHECK_CLUST(nxt_clust, 32);
- nxtsect = mydata->data_begin + - (nxt_clust * mydata->clust_size); + nxtsect = mydata->data_begin + + (nxt_clust * mydata->clust_size);
- root_cluster = nxt_clust; + root_cluster = nxt_clust;
- cursect = nxtsect; - j = 0; + cursect = nxtsect; + j = 0; + } } else { - cursect++; + if (j == PREFETCH_BLOCKS) + j = 0; + + rootdir_end = (++cursect - mydata->rootdir_sect >= + rootdir_size); }
/* If end of rootdir reached */ - if ((mydata->fatsize == 32 && fat32_end) || - (mydata->fatsize != 32 && j == rootdir_size)) { + if (rootdir_end) { if (dols == LS_ROOT) { printf("\n%d file(s), %d dir(s)\n\n", files, dirs);

With the previous code, the remaining prefetched sectors were read again after each sector. With this patch, each sector is read only once, thus making the prefetch useful.
Signed-off-by: Benoît Thébaudeau benoit.thebaudeau@advansee.com Cc: Wolfgang Denk wd@denx.de --- Changes for v2: - Patch renumbering because of the new v2 1/8. - Possible code style changes due to the new v2 1/8.
.../fs/fat/fat.c | 59 +++++++++++--------- 1 file changed, 33 insertions(+), 26 deletions(-)
diff --git u-boot-66714b1.orig/fs/fat/fat.c u-boot-66714b1/fs/fat/fat.c index 48c8844..fbc2d7d 100644 --- u-boot-66714b1.orig/fs/fat/fat.c +++ u-boot-66714b1/fs/fat/fat.c @@ -775,7 +775,7 @@ do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols) volume_info volinfo; fsdata datablock; fsdata *mydata = &datablock; - dir_entry *dentptr; + dir_entry *dentptr = NULL; __u16 prevcksum = 0xffff; char *subname = ""; __u32 cursect; @@ -874,19 +874,21 @@ do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols) while (1) { int i;
- debug("FAT read sect=%d, clust_size=%d, DIRENTSPERBLOCK=%zd\n", - cursect, mydata->clust_size, DIRENTSPERBLOCK); + if (j == 0) { + debug("FAT read sect=%d, clust_size=%d, DIRENTSPERBLOCK=%zd\n", + cursect, mydata->clust_size, DIRENTSPERBLOCK);
- if (disk_read(cursect, - (mydata->fatsize == 32) ? - (mydata->clust_size) : - PREFETCH_BLOCKS, - do_fat_read_block) < 0) { - debug("Error: reading rootdir block\n"); - goto exit; - } + if (disk_read(cursect, + (mydata->fatsize == 32) ? + (mydata->clust_size) : + PREFETCH_BLOCKS, + do_fat_read_block) < 0) { + debug("Error: reading rootdir block\n"); + goto exit; + }
- dentptr = (dir_entry *) do_fat_read_block; + dentptr = (dir_entry *) do_fat_read_block; + }
for (i = 0; i < DIRENTSPERBLOCK; i++) { char s_name[14], l_name[VFAT_MAXLEN_BYTES]; @@ -1028,28 +1030,33 @@ do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols) * completely processed. */ ++j; - int fat32_end = 0; - if ((mydata->fatsize == 32) && (j == mydata->clust_size)) { - int nxtsect = 0; - int nxt_clust = 0; + int rootdir_end = 0; + if (mydata->fatsize == 32) { + if (j == mydata->clust_size) { + int nxtsect = 0; + int nxt_clust = 0;
- nxt_clust = get_fatent(mydata, root_cluster); - fat32_end = CHECK_CLUST(nxt_clust, 32); + nxt_clust = get_fatent(mydata, root_cluster); + rootdir_end = CHECK_CLUST(nxt_clust, 32);
- nxtsect = mydata->data_begin + - (nxt_clust * mydata->clust_size); + nxtsect = mydata->data_begin + + (nxt_clust * mydata->clust_size);
- root_cluster = nxt_clust; + root_cluster = nxt_clust;
- cursect = nxtsect; - j = 0; + cursect = nxtsect; + j = 0; + } } else { - cursect++; + if (j == PREFETCH_BLOCKS) + j = 0; + + rootdir_end = (++cursect - mydata->rootdir_sect >= + rootdir_size); }
/* If end of rootdir reached */ - if ((mydata->fatsize == 32 && fat32_end) || - (mydata->fatsize != 32 && j == rootdir_size)) { + if (rootdir_end) { if (dols == LS_ROOT) { printf("\n%d file(s), %d dir(s)\n\n", files, dirs);

Dear Benoît Thébaudeau,
In message 1342599378.332558.1342790412010.JavaMail.root@advansee.com you wrote:
With the previous code, the remaining prefetched sectors were read again af> ter each sector. With this patch, each sector is read only once, thus making th> e prefetch useful.
Signed-off-by: Benoît Thébaudeau benoit.thebaudeau@advansee.com Cc: Wolfgang Denk wd@denx.de
Changes for v2:
- Patch renumbering because of the new v2 1/8.
- Possible code style changes due to the new v2 1/8.
.../fs/fat/fat.c | 59 +++++++++++-----> ---- 1 file changed, 33 insertions(+), 26 deletions(-)
Applied, thanks.
Best regards,
Wolfgang Denk
participants (2)
-
Benoît Thébaudeau
-
Wolfgang Denk