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Message-ID: <20070613185316.GX13465@halcrow.austin.ibm.com>
Date: Wed, 13 Jun 2007 13:53:16 -0500
From: Michael Halcrow <mhalcrow@...ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: "David J. Kleikamp" <shaggy@...ibm.com>, trevor.highland@...il.com,
LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] eCryptfs: fix write zeros behavior
This patch fixes the processes involved in wiping regions of the data
during truncate and write events, fixing a kernel hang in 2.6.22-rc4
while assuring that zero values are written out to the appropriate
locations during events in which the i_size will change.
The range passed to ecryptfs_truncate() from ecryptfs_prepare_write()
includes the page that is the object of ecryptfs_prepare_write(). This
leads to a kernel hang as read_cache_page() is executed on the same
page in the ecryptfs_truncate() execution path. This patch remedies
this by limiting the range passed to ecryptfs_truncate() so as to
exclude the page that is the object of ecryptfs_prepare_write(); it
also adds code to ecryptfs_prepare_write() to zero out the region of
its own page when writing past the i_size position. This patch also
modifies ecryptfs_truncate() so that when a file is truncated to a
smaller size, eCryptfs will zero out the contents of the new last page
from the new size through to the end of the last page.
Signed-off-by: Michael Halcrow <mhalcrow@...ibm.com>
---
fs/ecryptfs/ecryptfs_kernel.h | 2 +
fs/ecryptfs/inode.c | 19 ++++++++++++++
fs/ecryptfs/mmap.c | 53 ++++++++++++++++++++++------------------
3 files changed, 50 insertions(+), 24 deletions(-)
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 403e3ba..1b9dd9a 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -580,5 +580,7 @@ void
ecryptfs_write_header_metadata(char *virt,
struct ecryptfs_crypt_stat *crypt_stat,
size_t *written);
+int ecryptfs_write_zeros(struct file *file, pgoff_t index, int start,
+ int num_zeros);
#endif /* #ifndef ECRYPTFS_KERNEL_H */
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 1548be2..0981ae3 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -800,6 +800,25 @@ int ecryptfs_truncate(struct dentry *dentry, loff_t new_length)
goto out_fput;
}
} else { /* new_length < i_size_read(inode) */
+ pgoff_t index = 0;
+ int end_pos_in_page = -1;
+
+ if (new_length != 0) {
+ index = ((new_length - 1) >> PAGE_CACHE_SHIFT);
+ end_pos_in_page = ((new_length - 1) & ~PAGE_CACHE_MASK);
+ }
+ if (end_pos_in_page != (PAGE_CACHE_SIZE - 1)) {
+ if ((rc = ecryptfs_write_zeros(&fake_ecryptfs_file,
+ index,
+ (end_pos_in_page + 1),
+ ((PAGE_CACHE_SIZE - 1)
+ - end_pos_in_page)))) {
+ printk(KERN_ERR "Error attempting to zero out "
+ "the remainder of the end page on "
+ "reducing truncate; rc = [%d]\n", rc);
+ goto out_fput;
+ }
+ }
vmtruncate(inode, new_length);
rc = ecryptfs_write_inode_size_to_metadata(
lower_file, lower_dentry->d_inode, inode, dentry,
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 55cec98..6df410c 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -56,9 +56,6 @@ static struct page *ecryptfs_get1page(struct file *file, int index)
return read_mapping_page(mapping, index, (void *)file);
}
-static
-int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros);
-
/**
* ecryptfs_fill_zeros
* @file: The ecryptfs file
@@ -101,10 +98,13 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length)
if (old_end_page_index == new_end_page_index) {
/* Start and end are in the same page; we just need to
* set a portion of the existing page to zero's */
- rc = write_zeros(file, index, (old_end_pos_in_page + 1),
- (new_end_pos_in_page - old_end_pos_in_page));
+ rc = ecryptfs_write_zeros(file, index,
+ (old_end_pos_in_page + 1),
+ (new_end_pos_in_page
+ - old_end_pos_in_page));
if (rc)
- ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "
+ ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros("
+ "file=[%p], "
"index=[0x%.16x], "
"old_end_pos_in_page=[d], "
"(PAGE_CACHE_SIZE - new_end_pos_in_page"
@@ -117,10 +117,10 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length)
goto out;
}
/* Fill the remainder of the previous last page with zeros */
- rc = write_zeros(file, index, (old_end_pos_in_page + 1),
+ rc = ecryptfs_write_zeros(file, index, (old_end_pos_in_page + 1),
((PAGE_CACHE_SIZE - 1) - old_end_pos_in_page));
if (rc) {
- ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "
+ ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros(file=[%p], "
"index=[0x%.16x], old_end_pos_in_page=[d], "
"(PAGE_CACHE_SIZE - old_end_pos_in_page)=[d]) "
"returned [%d]\n", file, index,
@@ -131,9 +131,10 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length)
index++;
while (index < new_end_page_index) {
/* Fill all intermediate pages with zeros */
- rc = write_zeros(file, index, 0, PAGE_CACHE_SIZE);
+ rc = ecryptfs_write_zeros(file, index, 0, PAGE_CACHE_SIZE);
if (rc) {
- ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "
+ ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros("
+ "file=[%p], "
"index=[0x%.16x], "
"old_end_pos_in_page=[d], "
"(PAGE_CACHE_SIZE - new_end_pos_in_page"
@@ -149,9 +150,9 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length)
}
/* Fill the portion at the beginning of the last new page with
* zero's */
- rc = write_zeros(file, index, 0, (new_end_pos_in_page + 1));
+ rc = ecryptfs_write_zeros(file, index, 0, (new_end_pos_in_page + 1));
if (rc) {
- ecryptfs_printk(KERN_ERR, "write_zeros(file="
+ ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros(file="
"[%p], index=[0x%.16x], 0, "
"new_end_pos_in_page=[%d]"
"returned [%d]\n", file, index,
@@ -400,7 +401,6 @@ out:
static int ecryptfs_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
- loff_t pos;
int rc = 0;
if (from == 0 && to == PAGE_CACHE_SIZE)
@@ -408,14 +408,19 @@ static int ecryptfs_prepare_write(struct file *file, struct page *page,
up to date. */
if (!PageUptodate(page))
rc = ecryptfs_do_readpage(file, page, page->index);
- pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
- if (pos > i_size_read(page->mapping->host)) {
- rc = ecryptfs_truncate(file->f_path.dentry, pos);
- if (rc) {
- printk(KERN_ERR "Error on attempt to "
- "truncate to (higher) offset [%lld];"
- " rc = [%d]\n", pos, rc);
- goto out;
+ 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)) {
+ rc = ecryptfs_truncate(file->f_path.dentry,
+ end_of_prev_pg_pos);
+ if (rc) {
+ printk(KERN_ERR "Error on attempt to "
+ "truncate to (higher) offset [%lld];"
+ " rc = [%d]\n", end_of_prev_pg_pos, rc);
+ goto out;
+ }
}
}
out:
@@ -753,7 +758,7 @@ out:
}
/**
- * write_zeros
+ * ecryptfs_write_zeros
* @file: The ecryptfs file
* @index: The index in which we are writing
* @start: The position after the last block of data
@@ -763,8 +768,8 @@ out:
*
* (start + num_zeros) must be less than or equal to PAGE_CACHE_SIZE
*/
-static
-int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
+int
+ecryptfs_write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
{
int rc = 0;
struct page *tmp_page;
--
1.4.4.4
-
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