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mm/filemap: drop check for truncated page after I/O

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If the I/O completed successfully, the page will remain Uptodate, even
if it is subsequently truncated.  If the I/O completed with an error,
this check would cause us to retry the I/O if the page were truncated
before we woke up.  There is no need to retry the I/O; the I/O to fill
the page failed, so we can legitimately just return -EIO.

This code was originally added by commit 56f0d5fe6851 ("[PATCH]
readpage-vs-invalidate fix") in 2005 (this commit ID is from the
linux-fullhistory tree; it is also commit ba1f08f14b52 in tglx-history).

At the time, truncate_complete_page() called ClearPageUptodate(), and so
this was fixing a real bug.  In 2008, commit 84209e02de ("mm: dont clear
PG_uptodate on truncate/invalidate") removed the call to
ClearPageUptodate, and this check has been unnecessary ever since.

It doesn't do any real harm, but there's no need to keep it.

Link: https://lkml.kernel.org/r/20210303222547.1056428-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2021-04-29 22:55:29 -07:00 committed by Linus Torvalds
parent d31fa86a27
commit 79e3094c53
1 changed files with 0 additions and 2 deletions
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2
mm/filemap.c
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@ -2348,8 +2348,6 @@ static int filemap_read_page(struct file *file, struct address_space *mapping,
return error;
if (PageUptodate(page))
return 0;
if (!page->mapping) /* page truncated */
return AOP_TRUNCATED_PAGE;
shrink_readahead_size_eio(&file->f_ra);
return -EIO;
}