fs: fat: refactor write interface for a file offset
The current write implementation is quite simple: remove existing clusters and then allocating new ones and filling them with data. This, inevitably, enforces always writing from the beginning of a file. As the first step to lift this restriction, fat_file_write() and set_contents() are modified to accept an additional parameter, file offset and further re-factored so that, in the next patch, all the necessary code will be put into set_contents(). 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
4ced2039dc
commit
704df6aa0a
@ -528,6 +528,42 @@ static int clear_fatent(fsdata *mydata, __u32 entry)
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return 0;
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}
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/*
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* Set start cluster in directory entry
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*/
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static void set_start_cluster(const fsdata *mydata, dir_entry *dentptr,
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__u32 start_cluster)
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{
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if (mydata->fatsize == 32)
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dentptr->starthi =
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cpu_to_le16((start_cluster & 0xffff0000) >> 16);
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dentptr->start = cpu_to_le16(start_cluster & 0xffff);
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}
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/*
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* Check whether adding a file makes the file system to
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* exceed the size of the block device
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* Return -1 when overflow occurs, otherwise return 0
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*/
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static int check_overflow(fsdata *mydata, __u32 clustnum, loff_t size)
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{
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__u32 startsect, sect_num, offset;
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if (clustnum > 0)
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startsect = clust_to_sect(mydata, clustnum);
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else
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startsect = mydata->rootdir_sect;
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sect_num = div_u64_rem(size, mydata->sect_size, &offset);
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if (offset != 0)
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sect_num++;
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if (startsect + sect_num > total_sector)
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return -1;
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return 0;
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}
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/*
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* Write at most 'maxsize' bytes from 'buffer' into
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* the file associated with 'dentptr'
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@ -535,29 +571,36 @@ static int clear_fatent(fsdata *mydata, __u32 entry)
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* or return -1 on fatal errors.
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*/
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static int
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set_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
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loff_t maxsize, loff_t *gotsize)
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set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
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loff_t maxsize, loff_t *gotsize)
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{
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loff_t filesize = FAT2CPU32(dentptr->size);
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loff_t filesize;
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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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*gotsize = 0;
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debug("Filesize: %llu bytes\n", filesize);
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if (maxsize > 0 && filesize > maxsize)
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filesize = maxsize;
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filesize = maxsize;
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debug("%llu bytes\n", filesize);
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if (!curclust) {
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if (filesize) {
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debug("error: nonempty clusterless file!\n");
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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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return -1;
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}
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return 0;
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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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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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}
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actsize = bytesperclust;
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@ -568,6 +611,7 @@ set_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
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newclust = determine_fatent(mydata, endclust);
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if ((newclust - 1) != endclust)
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/* write to <curclust..endclust> */
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goto getit;
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if (CHECK_CLUST(newclust, mydata->fatsize)) {
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@ -614,18 +658,8 @@ getit:
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actsize = bytesperclust;
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curclust = endclust = newclust;
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} while (1);
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}
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/*
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* Set start cluster in directory entry
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*/
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static void set_start_cluster(const fsdata *mydata, dir_entry *dentptr,
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__u32 start_cluster)
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{
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if (mydata->fatsize == 32)
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dentptr->starthi =
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cpu_to_le16((start_cluster & 0xffff0000) >> 16);
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dentptr->start = cpu_to_le16(start_cluster & 0xffff);
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return 0;
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}
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/*
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@ -642,31 +676,6 @@ static void fill_dentry(fsdata *mydata, dir_entry *dentptr,
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set_name(dentptr, filename);
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}
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/*
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* Check whether adding a file makes the file system to
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* exceed the size of the block device
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* Return -1 when overflow occurs, otherwise return 0
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*/
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static int check_overflow(fsdata *mydata, __u32 clustnum, loff_t size)
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{
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__u32 startsect, sect_num, offset;
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if (clustnum > 0) {
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startsect = clust_to_sect(mydata, clustnum);
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} else {
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startsect = mydata->rootdir_sect;
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}
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sect_num = div_u64_rem(size, mydata->sect_size, &offset);
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if (offset != 0)
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sect_num++;
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if (startsect + sect_num > total_sector)
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return -1;
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return 0;
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}
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/*
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* Find a directory entry based on filename or start cluster number
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* If the directory entry is not found,
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@ -784,11 +793,10 @@ static int normalize_longname(char *l_filename, const char *filename)
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return 0;
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}
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static int do_fat_write(const char *filename, void *buffer, loff_t size,
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loff_t *actwrite)
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int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
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loff_t size, loff_t *actwrite)
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{
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dir_entry *retdent;
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__u32 start_cluster;
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fsdata datablock = { .fatbuf = NULL, };
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fsdata *mydata = &datablock;
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fat_itr *itr = NULL;
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@ -796,6 +804,8 @@ static int do_fat_write(const char *filename, void *buffer, loff_t size,
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char *filename_copy, *parent, *basename;
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char l_filename[VFAT_MAXLEN_BYTES];
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debug("writing %s\n", filename);
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filename_copy = strdup(filename);
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if (!filename_copy)
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return -ENOMEM;
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@ -839,47 +849,8 @@ static int do_fat_write(const char *filename, void *buffer, loff_t size,
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goto exit;
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}
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/* Update file size and start_cluster in a directory entry */
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retdent->size = cpu_to_le32(size);
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start_cluster = START(retdent);
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if (start_cluster) {
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if (size) {
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ret = check_overflow(mydata, start_cluster,
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size);
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if (ret) {
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printf("Error: %llu overflow\n", size);
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ret = -ENOSPC;
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goto exit;
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}
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}
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ret = clear_fatent(mydata, start_cluster);
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if (ret) {
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printf("Error: clearing FAT entries\n");
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ret = -EIO;
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goto exit;
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}
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if (!size)
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set_start_cluster(mydata, retdent, 0);
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} else if (size) {
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ret = start_cluster = find_empty_cluster(mydata);
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if (ret < 0) {
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printf("Error: finding empty cluster\n");
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ret = -ENOSPC;
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goto exit;
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}
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ret = check_overflow(mydata, start_cluster, size);
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if (ret) {
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printf("Error: %llu overflow\n", size);
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ret = -ENOSPC;
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goto exit;
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}
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set_start_cluster(mydata, retdent, start_cluster);
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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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/* Create a new file */
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@ -907,32 +878,13 @@ static int do_fat_write(const char *filename, void *buffer, loff_t size,
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goto exit;
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}
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if (size) {
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ret = start_cluster = find_empty_cluster(mydata);
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if (ret < 0) {
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printf("Error: finding empty cluster\n");
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ret = -ENOSPC;
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goto exit;
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}
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ret = check_overflow(mydata, start_cluster, size);
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if (ret) {
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printf("Error: %llu overflow\n", size);
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ret = -ENOSPC;
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goto exit;
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}
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} else {
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start_cluster = 0;
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}
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/* Set attribute as archive for regular file */
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fill_dentry(itr->fsdata, itr->dent, filename,
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start_cluster, size, 0x20);
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fill_dentry(itr->fsdata, itr->dent, filename, 0, size, 0x20);
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retdent = itr->dent;
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}
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ret = set_contents(mydata, retdent, buffer, size, actwrite);
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ret = set_contents(mydata, retdent, pos, buffer, size, actwrite);
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if (ret < 0) {
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printf("Error: writing contents\n");
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ret = -EIO;
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@ -971,6 +923,5 @@ int file_fat_write(const char *filename, void *buffer, loff_t offset,
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return -EINVAL;
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}
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printf("writing %s\n", filename);
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return do_fat_write(filename, buffer, maxsize, actwrite);
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return file_fat_write_at(filename, offset, buffer, maxsize, actwrite);
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}
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