aboutsummaryrefslogtreecommitdiffstats
path: root/fs
diff options
context:
space:
mode:
authorJens Axboe <jens.axboe@oracle.com>2007-06-07 07:39:42 (GMT)
committerJens Axboe <jens.axboe@oracle.com>2007-06-08 06:34:11 (GMT)
commit620a324b744a7d66c3c45a83042f8e7fc9fc5a04 (patch)
tree07bf593206a2f38a28ba97811572d036c32b7927 /fs
parent475ecade683566b19ebb84972de864039ac5fce3 (diff)
splice: __generic_file_splice_read: fix read/truncate race
Original patch and description from Neil Brown <neilb@suse.de>, 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 <jens.axboe@oracle.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/splice.c46
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;

Privacy Policy