[U-Boot] [PATCH v2 10/23] fs: fat: refactor write interface for a file offset
AKASHI Takahiro
takahiro.akashi at linaro.org
Tue Sep 4 07:49:35 UTC 2018
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 at linaro.org>
---
fs/fat/fat_write.c | 179 ++++++++++++++++-----------------------------
1 file changed, 65 insertions(+), 114 deletions(-)
diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
index cc55c94f1b72..5db7830ad43c 100644
--- a/fs/fat/fat_write.c
+++ b/fs/fat/fat_write.c
@@ -528,6 +528,42 @@ static int clear_fatent(fsdata *mydata, __u32 entry)
return 0;
}
+/*
+ * Set start cluster in directory entry
+ */
+static void set_start_cluster(const fsdata *mydata, dir_entry *dentptr,
+ __u32 start_cluster)
+{
+ if (mydata->fatsize == 32)
+ dentptr->starthi =
+ cpu_to_le16((start_cluster & 0xffff0000) >> 16);
+ dentptr->start = cpu_to_le16(start_cluster & 0xffff);
+}
+
+/*
+ * Check whether adding a file makes the file system to
+ * exceed the size of the block device
+ * Return -1 when overflow occurs, otherwise return 0
+ */
+static int check_overflow(fsdata *mydata, __u32 clustnum, loff_t size)
+{
+ __u32 startsect, sect_num, offset;
+
+ if (clustnum > 0)
+ startsect = clust_to_sect(mydata, clustnum);
+ else
+ startsect = mydata->rootdir_sect;
+
+ sect_num = div_u64_rem(size, mydata->sect_size, &offset);
+
+ if (offset != 0)
+ sect_num++;
+
+ if (startsect + sect_num > total_sector)
+ return -1;
+ return 0;
+}
+
/*
* Write at most 'maxsize' bytes from 'buffer' into
* the file associated with 'dentptr'
@@ -535,29 +571,36 @@ static int clear_fatent(fsdata *mydata, __u32 entry)
* or return -1 on fatal errors.
*/
static int
-set_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
- loff_t maxsize, loff_t *gotsize)
+set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
+ loff_t maxsize, loff_t *gotsize)
{
- loff_t filesize = FAT2CPU32(dentptr->size);
+ loff_t filesize;
unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
__u32 curclust = START(dentptr);
__u32 endclust = 0, newclust = 0;
loff_t actsize;
*gotsize = 0;
- debug("Filesize: %llu bytes\n", filesize);
-
- if (maxsize > 0 && filesize > maxsize)
- filesize = maxsize;
+ filesize = maxsize;
debug("%llu bytes\n", filesize);
- if (!curclust) {
- if (filesize) {
- debug("error: nonempty clusterless file!\n");
+ if (curclust) {
+ /*
+ * release already-allocated clusters anyway
+ */
+ if (clear_fatent(mydata, curclust)) {
+ printf("Error: clearing FAT entries\n");
return -1;
}
- return 0;
+ }
+
+ curclust = find_empty_cluster(mydata);
+ set_start_cluster(mydata, dentptr, curclust);
+
+ if (check_overflow(mydata, curclust, filesize)) {
+ printf("Error: no space left: %llu\n", filesize);
+ return -1;
}
actsize = bytesperclust;
@@ -568,6 +611,7 @@ set_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
newclust = determine_fatent(mydata, endclust);
if ((newclust - 1) != endclust)
+ /* write to <curclust..endclust> */
goto getit;
if (CHECK_CLUST(newclust, mydata->fatsize)) {
@@ -614,18 +658,8 @@ getit:
actsize = bytesperclust;
curclust = endclust = newclust;
} while (1);
-}
-/*
- * Set start cluster in directory entry
- */
-static void set_start_cluster(const fsdata *mydata, dir_entry *dentptr,
- __u32 start_cluster)
-{
- if (mydata->fatsize == 32)
- dentptr->starthi =
- cpu_to_le16((start_cluster & 0xffff0000) >> 16);
- dentptr->start = cpu_to_le16(start_cluster & 0xffff);
+ return 0;
}
/*
@@ -642,31 +676,6 @@ static void fill_dentry(fsdata *mydata, dir_entry *dentptr,
set_name(dentptr, filename);
}
-/*
- * Check whether adding a file makes the file system to
- * exceed the size of the block device
- * Return -1 when overflow occurs, otherwise return 0
- */
-static int check_overflow(fsdata *mydata, __u32 clustnum, loff_t size)
-{
- __u32 startsect, sect_num, offset;
-
- if (clustnum > 0) {
- startsect = clust_to_sect(mydata, clustnum);
- } else {
- startsect = mydata->rootdir_sect;
- }
-
- sect_num = div_u64_rem(size, mydata->sect_size, &offset);
-
- if (offset != 0)
- sect_num++;
-
- if (startsect + sect_num > total_sector)
- return -1;
- return 0;
-}
-
/*
* Find a directory entry based on filename or start cluster number
* If the directory entry is not found,
@@ -784,11 +793,10 @@ static int normalize_longname(char *l_filename, const char *filename)
return 0;
}
-static int do_fat_write(const char *filename, void *buffer, loff_t size,
- loff_t *actwrite)
+int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
+ loff_t size, loff_t *actwrite)
{
dir_entry *retdent;
- __u32 start_cluster;
fsdata datablock = { .fatbuf = NULL, };
fsdata *mydata = &datablock;
fat_itr *itr = NULL;
@@ -796,6 +804,8 @@ static int do_fat_write(const char *filename, void *buffer, loff_t size,
char *filename_copy, *parent, *basename;
char l_filename[VFAT_MAXLEN_BYTES];
+ debug("writing %s\n", filename);
+
filename_copy = strdup(filename);
if (!filename_copy)
return -ENOMEM;
@@ -839,47 +849,8 @@ static int do_fat_write(const char *filename, void *buffer, loff_t size,
goto exit;
}
- /* Update file size and start_cluster in a directory entry */
- retdent->size = cpu_to_le32(size);
- start_cluster = START(retdent);
-
- if (start_cluster) {
- if (size) {
- ret = check_overflow(mydata, start_cluster,
- size);
- if (ret) {
- printf("Error: %llu overflow\n", size);
- ret = -ENOSPC;
- goto exit;
- }
- }
-
- ret = clear_fatent(mydata, start_cluster);
- if (ret) {
- printf("Error: clearing FAT entries\n");
- ret = -EIO;
- goto exit;
- }
-
- if (!size)
- set_start_cluster(mydata, retdent, 0);
- } else if (size) {
- ret = start_cluster = find_empty_cluster(mydata);
- if (ret < 0) {
- printf("Error: finding empty cluster\n");
- ret = -ENOSPC;
- goto exit;
- }
-
- ret = check_overflow(mydata, start_cluster, size);
- if (ret) {
- printf("Error: %llu overflow\n", size);
- ret = -ENOSPC;
- goto exit;
- }
-
- set_start_cluster(mydata, retdent, start_cluster);
- }
+ /* Update file size in a directory entry */
+ retdent->size = cpu_to_le32(pos + size);
} else {
/* Create a new file */
@@ -907,32 +878,13 @@ static int do_fat_write(const char *filename, void *buffer, loff_t size,
goto exit;
}
- if (size) {
- ret = start_cluster = find_empty_cluster(mydata);
- if (ret < 0) {
- printf("Error: finding empty cluster\n");
- ret = -ENOSPC;
- goto exit;
- }
-
- ret = check_overflow(mydata, start_cluster, size);
- if (ret) {
- printf("Error: %llu overflow\n", size);
- ret = -ENOSPC;
- goto exit;
- }
- } else {
- start_cluster = 0;
- }
-
/* Set attribute as archieve for regular file */
- fill_dentry(itr->fsdata, itr->dent, filename,
- start_cluster, size, 0x20);
+ fill_dentry(itr->fsdata, itr->dent, filename, 0, size, 0x20);
retdent = itr->dent;
}
- ret = set_contents(mydata, retdent, buffer, size, actwrite);
+ ret = set_contents(mydata, retdent, pos, buffer, size, actwrite);
if (ret < 0) {
printf("Error: writing contents\n");
ret = -EIO;
@@ -971,6 +923,5 @@ int file_fat_write(const char *filename, void *buffer, loff_t offset,
return -EINVAL;
}
- printf("writing %s\n", filename);
- return do_fat_write(filename, buffer, maxsize, actwrite);
+ return file_fat_write_at(filename, offset, buffer, maxsize, actwrite);
}
--
2.18.0
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