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Subject[patch 6/9] mm: be sure to trim blocks
Date
If prepare_write fails with AOP_TRUNCATED_PAGE, or if commit_write fails, then
we may have failed the write operation despite prepare_write having
instantiated blocks past i_size. Fix this, and consolidate the trimming into
one place.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c
@@ -2120,22 +2120,9 @@ generic_file_buffered_write(struct kiocb
}

status = a_ops->prepare_write(file, page, offset, offset+bytes);
- if (unlikely(status)) {
- loff_t isize = i_size_read(inode);
+ if (unlikely(status))
+ goto fs_write_aop_error;

- if (status != AOP_TRUNCATED_PAGE)
- unlock_page(page);
- page_cache_release(page);
- if (status == AOP_TRUNCATED_PAGE)
- continue;
- /*
- * prepare_write() may have instantiated a few blocks
- * outside i_size. Trim these off again.
- */
- if (pos + bytes > isize)
- vmtruncate(inode, isize);
- break;
- }
if (likely(nr_segs == 1))
copied = filemap_copy_from_user(page, offset,
buf, bytes);
@@ -2144,40 +2131,53 @@ generic_file_buffered_write(struct kiocb
cur_iov, iov_offset, bytes);
flush_dcache_page(page);
status = a_ops->commit_write(file, page, offset, offset+bytes);
- if (status == AOP_TRUNCATED_PAGE) {
- page_cache_release(page);
- continue;
+ if (unlikely(status < 0))
+ goto fs_write_aop_error;
+ if (unlikely(copied != bytes)) {
+ status = -EFAULT;
+ goto fs_write_aop_error;
}
- if (likely(copied > 0)) {
- if (!status)
- status = copied;
+ if (unlikely(status > 0)) /* filesystem did partial write */
+ copied = status;

- if (status >= 0) {
- written += status;
- count -= status;
- pos += status;
- buf += status;
- if (unlikely(nr_segs > 1)) {
- filemap_set_next_iovec(&cur_iov,
- &iov_offset, status);
- if (count)
- buf = cur_iov->iov_base +
- iov_offset;
- } else {
- iov_offset += status;
- }
+ if (likely(copied > 0)) {
+ written += copied;
+ count -= copied;
+ pos += copied;
+ buf += copied;
+ if (unlikely(nr_segs > 1)) {
+ filemap_set_next_iovec(&cur_iov,
+ &iov_offset, copied);
+ if (count)
+ buf = cur_iov->iov_base + iov_offset;
+ } else {
+ iov_offset += copied;
}
}
- if (unlikely(copied != bytes))
- if (status >= 0)
- status = -EFAULT;
unlock_page(page);
mark_page_accessed(page);
page_cache_release(page);
- if (status < 0)
- break;
balance_dirty_pages_ratelimited(mapping);
cond_resched();
+ continue;
+
+fs_write_aop_error:
+ if (status != AOP_TRUNCATED_PAGE)
+ unlock_page(page);
+ page_cache_release(page);
+
+ /*
+ * prepare_write() may have instantiated a few blocks
+ * outside i_size. Trim these off again. Don't need
+ * i_size_read because we hold i_mutex.
+ */
+ if (pos + bytes > inode->i_size)
+ vmtruncate(inode, inode->i_size);
+ if (status == AOP_TRUNCATED_PAGE)
+ continue;
+ else
+ break;
+
} while (count);
*ppos = pos;

-
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