ecryptfs: fix fsx data corruption problems
ecryptfs in 2.6.24-rc3 wasn't surviving fsx for me at all, dying after 4
ops. Generally, encountering problems with stale data and improperly
zeroed pages. An extending truncate + write for example would expose stale
data.
With the changes below I got to a million ops and beyond with all mmap ops
disabled - mmap still needs work. (A version of this patch on a RHEL5
kernel ran for over 110 million fsx ops)
I added a few comments as well, to the best of my understanding
as I read through the code.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Acked-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 16a7a55..32c5711 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -263,14 +263,13 @@
return 0;
}
+/* This function must zero any hole we create */
static int ecryptfs_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
int rc = 0;
+ loff_t prev_page_end_size;
- if (from == 0 && to == PAGE_CACHE_SIZE)
- goto out; /* If we are writing a full page, it will be
- up to date. */
if (!PageUptodate(page)) {
rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
PAGE_CACHE_SIZE,
@@ -283,22 +282,32 @@
} else
SetPageUptodate(page);
}
- if (page->index != 0) {
- loff_t end_of_prev_pg_pos =
- (((loff_t)page->index << PAGE_CACHE_SHIFT) - 1);
- if (end_of_prev_pg_pos > i_size_read(page->mapping->host)) {
+ prev_page_end_size = ((loff_t)page->index << PAGE_CACHE_SHIFT);
+
+ /*
+ * If creating a page or more of holes, zero them out via truncate.
+ * Note, this will increase i_size.
+ */
+ if (page->index != 0) {
+ if (prev_page_end_size > i_size_read(page->mapping->host)) {
rc = ecryptfs_truncate(file->f_path.dentry,
- end_of_prev_pg_pos);
+ prev_page_end_size);
if (rc) {
printk(KERN_ERR "Error on attempt to "
"truncate to (higher) offset [%lld];"
- " rc = [%d]\n", end_of_prev_pg_pos, rc);
+ " rc = [%d]\n", prev_page_end_size, rc);
goto out;
}
}
- if (end_of_prev_pg_pos + 1 > i_size_read(page->mapping->host))
- zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
+ }
+ /*
+ * Writing to a new page, and creating a small hole from start of page?
+ * Zero it out.
+ */
+ if ((i_size_read(page->mapping->host) == prev_page_end_size) &&
+ (from != 0)) {
+ zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
}
out:
return rc;
diff --git a/fs/ecryptfs/read_write.c b/fs/ecryptfs/read_write.c
index 6b7474a..948f576 100644
--- a/fs/ecryptfs/read_write.c
+++ b/fs/ecryptfs/read_write.c
@@ -124,6 +124,10 @@
loff_t pos;
int rc = 0;
+ /*
+ * if we are writing beyond current size, then start pos
+ * at the current size - we'll fill in zeros from there.
+ */
if (offset > ecryptfs_file_size)
pos = ecryptfs_file_size;
else
@@ -137,6 +141,7 @@
if (num_bytes > total_remaining_bytes)
num_bytes = total_remaining_bytes;
if (pos < offset) {
+ /* remaining zeros to write, up to destination offset */
size_t total_remaining_zeros = (offset - pos);
if (num_bytes > total_remaining_zeros)
@@ -167,17 +172,27 @@
}
}
ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
+
+ /*
+ * pos: where we're now writing, offset: where the request was
+ * If current pos is before request, we are filling zeros
+ * If we are at or beyond request, we are writing the *data*
+ * If we're in a fresh page beyond eof, zero it in either case
+ */
+ if (pos < offset || !start_offset_in_page) {
+ /* We are extending past the previous end of the file.
+ * Fill in zero values to the end of the page */
+ memset(((char *)ecryptfs_page_virt
+ + start_offset_in_page), 0,
+ PAGE_CACHE_SIZE - start_offset_in_page);
+ }
+
+ /* pos >= offset, we are now writing the data request */
if (pos >= offset) {
memcpy(((char *)ecryptfs_page_virt
+ start_offset_in_page),
(data + data_offset), num_bytes);
data_offset += num_bytes;
- } else {
- /* We are extending past the previous end of the file.
- * Fill in zero values up to the start of where we
- * will be writing data. */
- memset(((char *)ecryptfs_page_virt
- + start_offset_in_page), 0, num_bytes);
}
kunmap_atomic(ecryptfs_page_virt, KM_USER0);
flush_dcache_page(ecryptfs_page);
