[U-Boot] [PATCH 09/17] fs: fat: support write with non-zero offset
Heinrich Schuchardt
xypron.glpk at gmx.de
Fri Jul 20 17:46:49 UTC 2018
On 07/20/2018 04:57 AM, AKASHI Takahiro wrote:
> In this patch, all the necessary code for allowing for a file offset
> at write is implemented. What plays a major roll here is get_set_cluster(),
> which, in contrast to its counterpart, set_cluster(), only operates on
> already-allocated clusters, overwriting with data.
>
> So, with a file offset specified, set_contents() seeks and writes data
> with set_get_cluster() until the end of a file, and, once it reaches
> there, continues writing with set_cluster() for the rest.
>
> Please note that a file will be trimmed as a result of write operation if
> write ends before reaching file's end. This is an intended behavior
> in order to maitain compatibility with the current interface.
This does not match the EFI spec.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
When testing I observed that I could not write at an offset larger than
the file size. This does not match the EFI spec:
EFI_FILE_PROTOCOL.SetPosition():
seeking past the end of the file is allowed (a subsequent write would
grow the file).
Best regards
Heinrich
> ---
> fs/fat/fat_write.c | 287 ++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 272 insertions(+), 15 deletions(-)
>
> diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
> index 3a9c53e253..cc45a33876 100644
> --- a/fs/fat/fat_write.c
> +++ b/fs/fat/fat_write.c
> @@ -450,6 +450,120 @@ set_cluster(fsdata *mydata, __u32 clustnum, __u8 *buffer,
> return 0;
> }
>
> +static __u8 tmpbuf_cluster[MAX_CLUSTSIZE] __aligned(ARCH_DMA_MINALIGN);
> +
> +/*
> + * Read and modify data on existing and consecutive cluster blocks
> + */
> +static int
> +get_set_cluster(fsdata *mydata, __u32 clustnum, loff_t pos, __u8 *buffer,
> + loff_t size, loff_t *gotsize)
> +{
> + unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
> + __u32 startsect;
> + loff_t wsize;
> + int clustcount, i, ret;
> +
> + *gotsize = 0;
> + if (!size)
> + return 0;
> +
> + assert(pos < bytesperclust);
> + startsect = clust_to_sect(mydata, clustnum);
> +
> + debug("clustnum: %d, startsect: %d, pos: %lld\n", clustnum, startsect,
> + pos);
> +
> + /* partial write at beginning */
> + if (pos) {
> + wsize = min(bytesperclust - pos, size);
> + ret = disk_read(startsect, mydata->clust_size, tmpbuf_cluster);
> + if (ret != mydata->clust_size) {
> + debug("Error reading data (got %d)\n", ret);
> + return -1;
> + }
> +
> + memcpy(tmpbuf_cluster + pos, buffer, wsize);
> + ret = disk_write(startsect, mydata->clust_size, tmpbuf_cluster);
> + if (ret != mydata->clust_size) {
> + debug("Error writing data (got %d)\n", ret);
> + return -1;
> + }
> +
> + size -= wsize;
> + buffer += wsize;
> + *gotsize += wsize;
> +
> + startsect += mydata->clust_size;
> +
> + if (!size)
> + return 0;
> + }
> +
> + /* full-cluster write */
> + if (size >= bytesperclust) {
> + clustcount = lldiv(size, bytesperclust);
> +
> + if (!((unsigned long)buffer & (ARCH_DMA_MINALIGN - 1))) {
> + wsize = clustcount * bytesperclust;
> + ret = disk_write(startsect,
> + clustcount * mydata->clust_size,
> + buffer);
> + if (ret != clustcount * mydata->clust_size) {
> + debug("Error writing data (got %d)\n", ret);
> + return -1;
> + }
> +
> + size -= wsize;
> + buffer += wsize;
> + *gotsize += wsize;
> +
> + startsect += clustcount * mydata->clust_size;
> + } else {
> + for (i = 0; i < clustcount; i++) {
> + memcpy(tmpbuf_cluster, buffer, bytesperclust);
> + ret = disk_write(startsect, mydata->clust_size,
> + tmpbuf_cluster);
> + if (ret != mydata->clust_size) {
> + debug("Error writing data (got %d)\n",
> + ret);
> + return -1;
> + }
> +
> + size -= bytesperclust;
> + buffer += bytesperclust;
> + *gotsize += bytesperclust;
> +
> + startsect += mydata->clust_size;
> + }
> + }
> + }
> +
> + /* partial write at end */
> + if (size) {
> + wsize = size;
> + ret = disk_read(startsect, mydata->clust_size, tmpbuf_cluster);
> + if (ret != mydata->clust_size) {
> + debug("Error reading data (got %d)\n", ret);
> + return -1;
> + }
> + memcpy(tmpbuf_cluster, buffer, wsize);
> + ret = disk_write(startsect, mydata->clust_size, tmpbuf_cluster);
> + if (ret != mydata->clust_size) {
> + debug("Error writing data (got %d)\n", ret);
> + return -1;
> + }
> +
> + size -= wsize;
> + buffer += wsize;
> + *gotsize += wsize;
> + }
> +
> + assert(!size);
> +
> + return 0;
> +}
> +
> /*
> * Find the first empty cluster
> */
> @@ -579,26 +693,158 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
> unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
> __u32 curclust = START(dentptr);
> __u32 endclust = 0, newclust = 0;
> - loff_t actsize;
> + loff_t cur_pos, offset, actsize, wsize;
>
> *gotsize = 0;
> - filesize = maxsize;
> + filesize = pos + maxsize;
>
> debug("%llu bytes\n", filesize);
>
> - if (curclust) {
> - /*
> - * release already-allocated clusters anyway
> - */
> - if (clear_fatent(mydata, curclust)) {
> - printf("Error: clearing FAT entries\n");
> + if (!filesize) {
> + if (!curclust)
> + return 0;
> + if (!CHECK_CLUST(curclust, mydata->fatsize) ||
> + IS_LAST_CLUST(curclust, mydata->fatsize)) {
> + clear_fatent(mydata, curclust);
> + set_start_cluster(mydata, dentptr, 0);
> + return 0;
> + }
> + debug("curclust: 0x%x\n", curclust);
> + debug("Invalid FAT entry\n");
> + return -1;
> + }
> +
> + if (!curclust) {
> + assert(pos == 0);
> + goto set_clusters;
> + }
> +
> + /* go to cluster at pos */
> + cur_pos = bytesperclust;
> + while (1) {
> + if (pos <= cur_pos)
> + break;
> + if (IS_LAST_CLUST(curclust, mydata->fatsize))
> + break;
> +
> + newclust = get_fatent(mydata, curclust);
> + if (!IS_LAST_CLUST(newclust, mydata->fatsize) &&
> + CHECK_CLUST(newclust, mydata->fatsize)) {
> + debug("curclust: 0x%x\n", curclust);
> + debug("Invalid FAT entry\n");
> return -1;
> }
> +
> + cur_pos += bytesperclust;
> + curclust = newclust;
> + }
> + if (IS_LAST_CLUST(curclust, mydata->fatsize)) {
> + assert(pos == cur_pos);
> + goto set_clusters;
> }
>
> - curclust = find_empty_cluster(mydata);
> - set_start_cluster(mydata, dentptr, curclust);
> + assert(pos < cur_pos);
> + cur_pos -= bytesperclust;
>
> + /* overwrite */
> + assert(IS_LAST_CLUST(curclust, mydata->fatsize) ||
> + !CHECK_CLUST(curclust, mydata->fatsize));
> +
> + while (1) {
> + /* search for allocated consecutive clusters */
> + actsize = bytesperclust;
> + endclust = curclust;
> + while (1) {
> + if (filesize <= (cur_pos + actsize))
> + break;
> +
> + newclust = get_fatent(mydata, endclust);
> +
> + if (IS_LAST_CLUST(newclust, mydata->fatsize))
> + break;
> + if (CHECK_CLUST(newclust, mydata->fatsize)) {
> + debug("curclust: 0x%x\n", curclust);
> + debug("Invalid FAT entry\n");
> + return -1;
> + }
> +
> + actsize += bytesperclust;
> + endclust = newclust;
> + }
> +
> + /* overwrite to <curclust..endclust> */
> + if (pos < cur_pos)
> + offset = 0;
> + else
> + offset = pos - cur_pos;
> + wsize = min(cur_pos + actsize, filesize) - pos;
> + if (get_set_cluster(mydata, curclust, offset, buffer, wsize,
> + &actsize)) {
> + printf("Error get-and-setting cluster\n");
> + return -1;
> + }
> + buffer += wsize;
> + *gotsize += wsize;
> + cur_pos += offset + wsize;
> +
> + if (filesize <= cur_pos)
> + break;
> +
> + /* CHECK: newclust = get_fatent(mydata, endclust); */
> +
> + if (IS_LAST_CLUST(newclust, mydata->fatsize))
> + /* no more clusters */
> + break;
> +
> + curclust = newclust;
> + }
> +
> + if (filesize <= cur_pos) {
> + /* no more write */
> + newclust = get_fatent(mydata, endclust);
> + if (!IS_LAST_CLUST(newclust, mydata->fatsize)) {
> + /* truncate the rest */
> + clear_fatent(mydata, newclust);
> +
> + /* Mark end of file in FAT */
> + if (mydata->fatsize == 12)
> + newclust = 0xfff;
> + else if (mydata->fatsize == 16)
> + newclust = 0xffff;
> + else if (mydata->fatsize == 32)
> + newclust = 0xfffffff;
> + set_fatent_value(mydata, endclust, newclust);
> + }
> +
> + return 0;
> + }
> +
> + curclust = endclust;
> + filesize -= cur_pos;
> + assert(!(cur_pos % bytesperclust));
> +
> +set_clusters:
> + /* allocate and write */
> + assert(!pos);
> +
> + /* Assure that curclust is valid */
> + if (!curclust) {
> + curclust = find_empty_cluster(mydata);
> + set_start_cluster(mydata, dentptr, curclust);
> + } else {
> + newclust = get_fatent(mydata, curclust);
> +
> + if (IS_LAST_CLUST(newclust, mydata->fatsize)) {
> + newclust = determine_fatent(mydata, curclust);
> + set_fatent_value(mydata, curclust, newclust);
> + curclust = newclust;
> + } else {
> + debug("error: something wrong\n");
> + return -1;
> + }
> + }
> +
> + /* TODO: already partially written */
> if (check_overflow(mydata, curclust, filesize)) {
> printf("Error: no space left: %llu\n", filesize);
> return -1;
> @@ -852,6 +1098,16 @@ int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
> goto exit;
> }
>
> + /* A file exists */
> + if (pos == -1)
> + /* Append to the end */
> + pos = FAT2CPU32(retdent->size);
> + if (pos > retdent->size) {
> + /* No hole allowed */
> + ret = -EINVAL;
> + goto exit;
> + }
> +
> /* Update file size in a directory entry */
> retdent->size = cpu_to_le32(pos + size);
> } else {
> @@ -872,6 +1128,12 @@ int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
> goto exit;
> }
>
> + if (pos) {
> + /* No hole allowed */
> + ret = -EINVAL;
> + goto exit;
> + }
> +
> memset(itr->dent, 0, sizeof(*itr->dent));
>
> /* Set short name to set alias checksum field in dir_slot */
> @@ -921,10 +1183,5 @@ exit:
> int file_fat_write(const char *filename, void *buffer, loff_t offset,
> loff_t maxsize, loff_t *actwrite)
> {
> - if (offset != 0) {
> - printf("Error: non zero offset is currently not supported.\n");
> - return -EINVAL;
> - }
> -
> return file_fat_write_at(filename, offset, buffer, maxsize, actwrite);
> }
>
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