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 --- fs/fat/fat_write.c | 288 ++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 273 insertions(+), 15 deletions(-)
diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c index 5db7830ad43c..523abd62c9e9 100644 --- a/fs/fat/fat_write.c +++ b/fs/fat/fat_write.c @@ -450,6 +450,121 @@ 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 */ @@ -578,26 +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; @@ -849,6 +1096,16 @@ 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 { @@ -869,6 +1126,12 @@ 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 */ @@ -918,10 +1181,5 @@ 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); }