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-rw-r--r--mm/filemap.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 1ed4be2a7654..9c7334bafda8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -828,6 +828,32 @@ grab_cache_page_nowait(struct address_space *mapping, unsigned long index)
}
EXPORT_SYMBOL(grab_cache_page_nowait);
+/*
+ * CD/DVDs are error prone. When a medium error occurs, the driver may fail
+ * a _large_ part of the i/o request. Imagine the worst scenario:
+ *
+ * ---R__________________________________________B__________
+ * ^ reading here ^ bad block(assume 4k)
+ *
+ * read(R) => miss => readahead(R...B) => media error => frustrating retries
+ * => failing the whole request => read(R) => read(R+1) =>
+ * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
+ * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
+ * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
+ *
+ * It is going insane. Fix it by quickly scaling down the readahead size.
+ */
+static void shrink_readahead_size_eio(struct file *filp,
+ struct file_ra_state *ra)
+{
+ if (!ra->ra_pages)
+ return;
+
+ ra->ra_pages /= 4;
+ printk(KERN_WARNING "Reducing readahead size to %luK\n",
+ ra->ra_pages << (PAGE_CACHE_SHIFT - 10));
+}
+
/**
* do_generic_mapping_read - generic file read routine
* @mapping: address_space to be read
@@ -985,6 +1011,7 @@ readpage:
}
unlock_page(page);
error = -EIO;
+ shrink_readahead_size_eio(filp, &ra);
goto readpage_error;
}
unlock_page(page);
@@ -1522,6 +1549,7 @@ page_not_uptodate:
* Things didn't work out. Return zero to tell the
* mm layer so, possibly freeing the page cache page first.
*/
+ shrink_readahead_size_eio(file, ra);
page_cache_release(page);
return NULL;
}