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From: Dmitriy Monakhov <>
To: Linux Kernel <>
Subject: nobh_truncate_page question
Date: Thu, 08 Feb 2007 01:45:10 +0300	[thread overview]
Message-ID: <> (raw)

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);
                kunmap_atomic(kaddr, KM_USER0);
        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.

             reply	other threads:[~2007-02-07 22:44 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-07 22:45 Dmitriy Monakhov [this message]
2007-02-08  2:11 ` Andrew Morton

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