Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=620a324b744a7d66c3c45a83042f8e7fc9fc5a04
Commit: 620a324b744a7d66c3c45a83042f8e7fc9fc5a04
Parent: 475ecade683566b19ebb84972de864039ac5fce3
Author: Jens Axboe <[EMAIL PROTECTED]>
AuthorDate: Thu Jun 7 09:39:42 2007 +0200
Committer: Jens Axboe <[EMAIL PROTECTED]>
CommitDate: Fri Jun 8 08:34:11 2007 +0200
splice: __generic_file_splice_read: fix read/truncate race
Original patch and description from Neil Brown <[EMAIL PROTECTED]>,
merged and adapted to splice branch by me. Neils text follows:
__generic_file_splice_read() currently samples the i_size at the start
and doesn't do so again unless it needs to call ->readpage to load
a page. After ->readpage it has to re-sample i_size as a truncate
may have caused that page to be filled with zeros, and the read()
call should not see these.
However there are other activities that might cause ->readpage to be
called on a page between the time that __generic_file_splice_read()
samples i_size and when it finds that it has an uptodate page. These
include at least read-ahead and possibly another thread performing a
read
So we must sample i_size *after* it has an uptodate page. Thus the
current sampling at the start and after a read can be replaced with a
sampling before page addition into spd.
Signed-off-by: Jens Axboe <[EMAIL PROTECTED]>
---
fs/splice.c | 46 +++++++++++++++++++++++-----------------------
1 files changed, 23 insertions(+), 23 deletions(-)
diff --git a/fs/splice.c b/fs/splice.c
index 123fcdb..cb21136 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -413,37 +413,37 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
break;
}
+ }
+fill_it:
+ /*
+ * i_size must be checked after PageUptodate.
+ */
+ isize = i_size_read(mapping->host);
+ end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
+ if (unlikely(!isize || index > end_index))
+ break;
+
+ /*
+ * if this is the last page, see if we need to shrink
+ * the length and stop
+ */
+ if (end_index == index) {
+ unsigned int plen;
/*
- * i_size must be checked after ->readpage().
+ * max good bytes in this page
*/
- isize = i_size_read(mapping->host);
- end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
- if (unlikely(!isize || index > end_index))
+ plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
+ if (plen <= loff)
break;
/*
- * if this is the last page, see if we need to shrink
- * the length and stop
+ * force quit after adding this page
*/
- if (end_index == index) {
- unsigned int plen;
-
- /*
- * max good bytes in this page
- */
- plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
- if (plen <= loff)
- break;
-
- /*
- * force quit after adding this page
- */
- this_len = min(this_len, plen - loff);
- len = this_len;
- }
+ this_len = min(this_len, plen - loff);
+ len = this_len;
}
-fill_it:
+
partial[page_nr].offset = loff;
partial[page_nr].len = this_len;
len -= this_len;
-
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