fs: fat: support write with non-zero offset
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 maintain compatibility with the current interface. Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Signed-off-by: Alexander Graf <agraf@suse.de>
This commit is contained in:
AKASHI Takahiro
Alexander Graf
parent
704df6aa0a
commit
cb8af8af5b
@ -450,6 +450,121 @@ set_cluster(fsdata *mydata, __u32 clustnum, __u8 *buffer,
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return 0;
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}
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static __u8 tmpbuf_cluster[MAX_CLUSTSIZE] __aligned(ARCH_DMA_MINALIGN);
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/*
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* Read and modify data on existing and consecutive cluster blocks
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*/
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static int
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get_set_cluster(fsdata *mydata, __u32 clustnum, loff_t pos, __u8 *buffer,
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loff_t size, loff_t *gotsize)
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{
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unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
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__u32 startsect;
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loff_t wsize;
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int clustcount, i, ret;
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*gotsize = 0;
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if (!size)
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return 0;
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assert(pos < bytesperclust);
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startsect = clust_to_sect(mydata, clustnum);
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debug("clustnum: %d, startsect: %d, pos: %lld\n",
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clustnum, startsect, pos);
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/* partial write at beginning */
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if (pos) {
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wsize = min(bytesperclust - pos, size);
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ret = disk_read(startsect, mydata->clust_size, tmpbuf_cluster);
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if (ret != mydata->clust_size) {
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debug("Error reading data (got %d)\n", ret);
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return -1;
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}
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memcpy(tmpbuf_cluster + pos, buffer, wsize);
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ret = disk_write(startsect, mydata->clust_size, tmpbuf_cluster);
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if (ret != mydata->clust_size) {
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debug("Error writing data (got %d)\n", ret);
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return -1;
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}
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size -= wsize;
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buffer += wsize;
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*gotsize += wsize;
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startsect += mydata->clust_size;
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if (!size)
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return 0;
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}
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/* full-cluster write */
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if (size >= bytesperclust) {
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clustcount = lldiv(size, bytesperclust);
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if (!((unsigned long)buffer & (ARCH_DMA_MINALIGN - 1))) {
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wsize = clustcount * bytesperclust;
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ret = disk_write(startsect,
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clustcount * mydata->clust_size,
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buffer);
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if (ret != clustcount * mydata->clust_size) {
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debug("Error writing data (got %d)\n", ret);
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return -1;
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}
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size -= wsize;
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buffer += wsize;
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*gotsize += wsize;
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startsect += clustcount * mydata->clust_size;
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} else {
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for (i = 0; i < clustcount; i++) {
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memcpy(tmpbuf_cluster, buffer, bytesperclust);
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ret = disk_write(startsect,
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mydata->clust_size,
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tmpbuf_cluster);
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if (ret != mydata->clust_size) {
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debug("Error writing data (got %d)\n",
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ret);
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return -1;
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}
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size -= bytesperclust;
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buffer += bytesperclust;
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*gotsize += bytesperclust;
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startsect += mydata->clust_size;
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}
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}
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}
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/* partial write at end */
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if (size) {
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wsize = size;
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ret = disk_read(startsect, mydata->clust_size, tmpbuf_cluster);
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if (ret != mydata->clust_size) {
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debug("Error reading data (got %d)\n", ret);
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return -1;
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}
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memcpy(tmpbuf_cluster, buffer, wsize);
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ret = disk_write(startsect, mydata->clust_size, tmpbuf_cluster);
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if (ret != mydata->clust_size) {
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debug("Error writing data (got %d)\n", ret);
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return -1;
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}
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size -= wsize;
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buffer += wsize;
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*gotsize += wsize;
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}
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assert(!size);
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return 0;
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}
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/*
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* Find the first empty cluster
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*/
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@ -578,26 +693,158 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
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unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
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__u32 curclust = START(dentptr);
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__u32 endclust = 0, newclust = 0;
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loff_t actsize;
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loff_t cur_pos, offset, actsize, wsize;
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*gotsize = 0;
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filesize = maxsize;
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filesize = pos + maxsize;
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debug("%llu bytes\n", filesize);
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if (curclust) {
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/*
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* release already-allocated clusters anyway
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*/
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if (clear_fatent(mydata, curclust)) {
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printf("Error: clearing FAT entries\n");
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if (!filesize) {
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if (!curclust)
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return 0;
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if (!CHECK_CLUST(curclust, mydata->fatsize) ||
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IS_LAST_CLUST(curclust, mydata->fatsize)) {
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clear_fatent(mydata, curclust);
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set_start_cluster(mydata, dentptr, 0);
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return 0;
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}
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debug("curclust: 0x%x\n", curclust);
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debug("Invalid FAT entry\n");
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return -1;
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}
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if (!curclust) {
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assert(pos == 0);
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goto set_clusters;
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}
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/* go to cluster at pos */
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cur_pos = bytesperclust;
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while (1) {
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if (pos <= cur_pos)
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break;
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if (IS_LAST_CLUST(curclust, mydata->fatsize))
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break;
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newclust = get_fatent(mydata, curclust);
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if (!IS_LAST_CLUST(newclust, mydata->fatsize) &&
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CHECK_CLUST(newclust, mydata->fatsize)) {
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debug("curclust: 0x%x\n", curclust);
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debug("Invalid FAT entry\n");
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return -1;
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}
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cur_pos += bytesperclust;
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curclust = newclust;
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}
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if (IS_LAST_CLUST(curclust, mydata->fatsize)) {
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assert(pos == cur_pos);
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goto set_clusters;
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}
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assert(pos < cur_pos);
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cur_pos -= bytesperclust;
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/* overwrite */
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assert(IS_LAST_CLUST(curclust, mydata->fatsize) ||
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!CHECK_CLUST(curclust, mydata->fatsize));
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while (1) {
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/* search for allocated consecutive clusters */
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actsize = bytesperclust;
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endclust = curclust;
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while (1) {
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if (filesize <= (cur_pos + actsize))
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break;
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newclust = get_fatent(mydata, endclust);
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if (IS_LAST_CLUST(newclust, mydata->fatsize))
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break;
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if (CHECK_CLUST(newclust, mydata->fatsize)) {
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debug("curclust: 0x%x\n", curclust);
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debug("Invalid FAT entry\n");
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return -1;
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}
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actsize += bytesperclust;
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endclust = newclust;
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}
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/* overwrite to <curclust..endclust> */
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if (pos < cur_pos)
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offset = 0;
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else
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offset = pos - cur_pos;
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wsize = min(cur_pos + actsize, filesize) - pos;
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if (get_set_cluster(mydata, curclust, offset,
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buffer, wsize, &actsize)) {
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printf("Error get-and-setting cluster\n");
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return -1;
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}
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buffer += wsize;
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*gotsize += wsize;
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cur_pos += offset + wsize;
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if (filesize <= cur_pos)
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break;
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/* CHECK: newclust = get_fatent(mydata, endclust); */
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if (IS_LAST_CLUST(newclust, mydata->fatsize))
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/* no more clusters */
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break;
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curclust = newclust;
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}
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if (filesize <= cur_pos) {
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/* no more write */
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newclust = get_fatent(mydata, endclust);
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if (!IS_LAST_CLUST(newclust, mydata->fatsize)) {
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/* truncate the rest */
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clear_fatent(mydata, newclust);
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/* Mark end of file in FAT */
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if (mydata->fatsize == 12)
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newclust = 0xfff;
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else if (mydata->fatsize == 16)
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newclust = 0xffff;
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else if (mydata->fatsize == 32)
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newclust = 0xfffffff;
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set_fatent_value(mydata, endclust, newclust);
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}
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return 0;
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}
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curclust = endclust;
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filesize -= cur_pos;
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assert(!(cur_pos % bytesperclust));
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set_clusters:
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/* allocate and write */
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assert(!pos);
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/* Assure that curclust is valid */
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if (!curclust) {
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curclust = find_empty_cluster(mydata);
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set_start_cluster(mydata, dentptr, curclust);
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} else {
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newclust = get_fatent(mydata, curclust);
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if (IS_LAST_CLUST(newclust, mydata->fatsize)) {
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newclust = determine_fatent(mydata, curclust);
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set_fatent_value(mydata, curclust, newclust);
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curclust = newclust;
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} else {
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debug("error: something wrong\n");
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return -1;
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}
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}
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curclust = find_empty_cluster(mydata);
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set_start_cluster(mydata, dentptr, curclust);
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/* TODO: already partially written */
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if (check_overflow(mydata, curclust, filesize)) {
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printf("Error: no space left: %llu\n", filesize);
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return -1;
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@ -849,6 +1096,16 @@ int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
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goto exit;
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}
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/* A file exists */
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if (pos == -1)
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/* Append to the end */
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pos = FAT2CPU32(retdent->size);
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if (pos > retdent->size) {
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/* No hole allowed */
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ret = -EINVAL;
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goto exit;
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}
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/* Update file size in a directory entry */
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retdent->size = cpu_to_le32(pos + size);
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} else {
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@ -869,6 +1126,12 @@ int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
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goto exit;
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}
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if (pos) {
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/* No hole allowed */
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ret = -EINVAL;
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goto exit;
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}
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memset(itr->dent, 0, sizeof(*itr->dent));
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/* Set short name to set alias checksum field in dir_slot */
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@ -918,10 +1181,5 @@ exit:
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int file_fat_write(const char *filename, void *buffer, loff_t offset,
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loff_t maxsize, loff_t *actwrite)
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{
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if (offset != 0) {
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printf("Error: non zero offset is currently not supported.\n");
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return -EINVAL;
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}
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return file_fat_write_at(filename, offset, buffer, maxsize, actwrite);
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}
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