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ext4: use private version of page_zero_new_buffers() for data=journal mode
If there is a error while copying data from userspace into the page
cache during a write(2) system call, in data=journal mode, in
ext4_journalled_write_end() were using page_zero_new_buffers() from
fs/buffer.c. Unfortunately, this sets the buffer dirty flag, which is
no good if journalling is enabled. This is a long-standing bug that
goes back for years and years in ext3, but a combination of (a)
data=journal not being very common, (b) in many case it only results
in a warning message. and (c) only very rarely causes the kernel hang,
means that we only really noticed this as a problem when commit
998ef75ddb
caused this failure to happen frequently enough to cause
generic/208 to fail when run in data=journal mode.
The fix is to have our own version of this function that doesn't call
mark_dirty_buffer(), since we will end up calling
ext4_handle_dirty_metadata() on the buffer head(s) in questions very
shortly afterwards in ext4_journalled_write_end().
Thanks to Dave Hansen and Linus Torvalds for helping to identify the
root cause of the problem.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.com>
This commit is contained in:
parent
36086d43f6
commit
b90197b655
@ -1181,6 +1181,38 @@ errout:
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return ret ? ret : copied;
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}
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/*
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* This is a private version of page_zero_new_buffers() which doesn't
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* set the buffer to be dirty, since in data=journalled mode we need
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* to call ext4_handle_dirty_metadata() instead.
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*/
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static void zero_new_buffers(struct page *page, unsigned from, unsigned to)
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{
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unsigned int block_start = 0, block_end;
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struct buffer_head *head, *bh;
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bh = head = page_buffers(page);
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do {
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block_end = block_start + bh->b_size;
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if (buffer_new(bh)) {
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if (block_end > from && block_start < to) {
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if (!PageUptodate(page)) {
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unsigned start, size;
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start = max(from, block_start);
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size = min(to, block_end) - start;
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zero_user(page, start, size);
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set_buffer_uptodate(bh);
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}
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clear_buffer_new(bh);
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}
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}
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block_start = block_end;
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bh = bh->b_this_page;
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} while (bh != head);
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}
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static int ext4_journalled_write_end(struct file *file,
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struct address_space *mapping,
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loff_t pos, unsigned len, unsigned copied,
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@ -1207,7 +1239,7 @@ static int ext4_journalled_write_end(struct file *file,
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if (copied < len) {
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if (!PageUptodate(page))
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copied = 0;
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page_zero_new_buffers(page, from+copied, to);
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zero_new_buffers(page, from+copied, to);
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}
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ret = ext4_walk_page_buffers(handle, page_buffers(page), from,
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