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ecryptfs: fix fsx data corruption problems

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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>
This commit is contained in:
Eric Sandeen
2007-12-17 16:20:10 -08:00
committed by Linus Torvalds
parent 8998979cc1
commit 7a3f595cc8
2 changed files with 41 additions and 17 deletions
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27
fs/ecryptfs/read_write.c
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@@ -124,6 +124,10 @@ int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset,
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 @@ int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset,
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 @@ int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset,
}
}
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);