Could some one please explain me what's happens with nobh_truncate_page?
int nobh_truncate_page(struct address_space *mapping, loff_t from)
{
........
if ((offset & (blocksize - 1)) == 0)
goto out;
ret = -ENOMEM;
page = grab_cache_page(mapping, index);
if (!page)
goto out;
to = (offset + blocksize) & ~(blocksize - 1);
ret = a_ops->prepare_write(NULL, page, offset, to);
<<<<< This prepare_write() not balanced by appropriate commit_write()
<<<<< Currently this not is fatal because this function used only
<<<<< by ext2 and jfs witch unbalanced prepare/commit operations
<<<<< not painful.
if (ret == 0) {
kaddr = kmap_atomic(page, KM_USER0);
memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
set_page_dirty(page);
}
unlock_page(page);
page_cache_release(page);
out:
return ret;
}
But we can't just call commit_write after all job done because this result in
i_size increasing till block end. Where are two possible solutions:
a) Call ->commit_write() and then restore i_size to old value.
b) Leave code as it is now, but add warning comment about prepare/commit
balance violation.
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