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authorMichael Halcrow <mhalcrow@us.ibm.com>2007-05-23 13:58:15 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-23 20:14:15 -0700
commit53a2731f9310a66beaf55677229ab067c85ce4fa (patch)
tree6166f49b9205541a96696f648217c606cc9d9a0a /fs/ecryptfs/mmap.c
parent4acb3e2f97f41cf9b53182b494384467d3ceb304 (diff)
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eCryptfs: delay writing 0's after llseek until write
Delay writing 0's out in eCryptfs after a seek past the end of the file until data is actually written. http://www.opengroup.org/onlinepubs/009695399/functions/lseek.html ``The lseek() function shall not, by itself, extend the size of a file.'' Without this fix, applications that lseek() past the end of the file without writing will experience unexpected behavior. Signed-off-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>
Diffstat (limited to 'fs/ecryptfs/mmap.c')
-rw-r--r--fs/ecryptfs/mmap.c38
1 files changed, 35 insertions, 3 deletions
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 88ea6697908..55cec98a84e 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -376,9 +376,31 @@ out:
return 0;
}
+/**
+ * eCryptfs does not currently support holes. When writing after a
+ * seek past the end of the file, eCryptfs fills in 0's through to the
+ * current location. The code to fill in the 0's to all the
+ * intermediate pages calls ecryptfs_prepare_write_no_truncate().
+ */
+static int
+ecryptfs_prepare_write_no_truncate(struct file *file, struct page *page,
+ unsigned from, unsigned to)
+{
+ int rc = 0;
+
+ 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_do_readpage(file, page, page->index);
+out:
+ return rc;
+}
+
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)
@@ -386,6 +408,16 @@ 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;
+ }
+ }
out:
return rc;
}
@@ -744,10 +776,10 @@ int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
rc = PTR_ERR(tmp_page);
goto out;
}
- rc = ecryptfs_prepare_write(file, tmp_page, start, start + num_zeros);
- if (rc) {
+ if ((rc = ecryptfs_prepare_write_no_truncate(file, tmp_page, start,
+ (start + num_zeros)))) {
ecryptfs_printk(KERN_ERR, "Error preparing to write zero's "
- "to remainder of page at index [0x%.16x]\n",
+ "to page at index [0x%.16x]\n",
index);
page_cache_release(tmp_page);
goto out;