Any particular reason why I shouldn't do this?
Other than the fact that you need shared writeable mmap (which JFFS2
doesn't support) in order to use it, that is -- but I'll get to that.
diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
index 5a98aa8..a8e4727 100644
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -25,7 +25,8 @@ static int jffs2_write_end(struct file *filp, struct address_space *mapping,
static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata);
-static int jffs2_readpage (struct file *filp, struct page *pg);
+static int jffs2_readpage(struct file *filp, struct page *pg);
+static void jffs2_truncate_range(struct inode *inode, loff_t start, loff_t end);
int jffs2_fsync(struct file *filp, struct dentry *dentry, int datasync)
{
@@ -56,6 +57,7 @@ const struct file_operations jffs2_file_operations =
const struct inode_operations jffs2_file_inode_operations =
{
+ .truncate_range=jffs2_truncate_range,
.permission = jffs2_permission,
.setattr = jffs2_setattr,
.setxattr = jffs2_setxattr,
@@ -319,3 +321,81 @@ static int jffs2_write_end(struct file *filp, struct address_space *mapping,
page_cache_release(pg);
return writtenlen > 0 ? writtenlen : ret;
}
+
+static void jffs2_truncate_range(struct inode *inode, loff_t start, loff_t end)
+{
+ struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode);
+ struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
+ struct jffs2_raw_inode *ri;
+ struct jffs2_full_dnode *fn;
+ uint32_t alloclen;
+ uint32_t len;
+ int alloc_type = ALLOC_NORMAL;
+ int ret;
+
+ if (end >= inode->i_size)
+ end = inode->i_size - 1;
+
+ len = end - start + 1;
+
+ if (len >= PAGE_SIZE)
+ alloc_type = ALLOC_DELETION;
+
+ ri = jffs2_alloc_raw_inode();
+ if (!ri) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ ret = jffs2_reserve_space(c, sizeof(ri), &alloclen,
+ alloc_type, JFFS2_SUMMARY_INODE_SIZE);
+ if (ret)
+ goto out_free;
+
+ mutex_lock(&f->sem);
+
+ ri->magic = cpu_to_je16(JFFS2_MAGIC_BITMASK);
+ ri->nodetype = cpu_to_je16(JFFS2_NODETYPE_INODE);
+ ri->totlen = cpu_to_je32(sizeof(*ri));
+ ri->hdr_crc = cpu_to_je32(crc32(0, ri,
+ sizeof(struct jffs2_unknown_node) - 4));
+
+ ri->ino = cpu_to_je32(inode->i_ino);
+ ri->mode = cpu_to_jemode(inode->i_mode);
+ ri->uid = cpu_to_je16(inode->i_uid);
+ ri->gid = cpu_to_je16(inode->i_gid);
+ ri->isize = cpu_to_je32((uint32_t)inode->i_size);
+ ri->atime = ri->ctime = ri->mtime = cpu_to_je32(get_seconds());
+
+ ri->version = cpu_to_je32(++f->highest_version);
+ ri->offset = cpu_to_je32(start);
+ ri->csize = cpu_to_je32(0);
+ ri->dsize = cpu_to_je32(len);
+ ri->compr = JFFS2_COMPR_ZERO;
+ ri->usercompr = 0;
+ ri->node_crc = cpu_to_je32(crc32(0, ri, sizeof(*ri)-8));
+ ri->data_crc = cpu_to_je32(0);
+
+ fn = jffs2_write_dnode(c, f, ri, NULL, 0, alloc_type);
+
+ if (IS_ERR(fn)) {
+ ret = PTR_ERR(fn);
+ goto out_unlock;
+ }
+
+ ret = jffs2_add_full_dnode_to_inode(c, f, fn);
+ if (ret) {
+ printk(KERN_WARNING "jffs2_add_full_dnode.. failed in %s: %d\n",
+ __func__, ret);
+ jffs2_mark_node_obsolete(c, fn->raw);
+ goto out;
+ }
+
+ out_unlock:
+ mutex_unlock(&f->sem);
+ jffs2_complete_reservation(c);
+ out_free:
+ jffs2_free_raw_inode(ri);
+ out:
+ /* return ret; */ ;
+}
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@xxxxxxxxx Intel Corporation
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