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ext4: fix partial page writes 

While running extended fsx tests to verify the preceeding patches,
a similar bug was also found in the write operation

When ever a write operation begins or ends in a hole,
or extends EOF, the partial page contained in the hole
or beyond EOF needs to be zeroed out.

To correct this the new ext4_discard_partial_page_buffers_no_lock
routine is used to zero out the partial page, but only for buffer
heads that are already unmapped.

Signed-off-by: Allison Henderson <achender@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Allison Henderson 2011-09-06 21:53:01 -04:00 committed by Theodore Ts'o
parent 189e868fa8
commit 02fac1297e
1 changed files with 19 additions and 0 deletions
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19
fs/ext4/inode.c
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@ -2255,6 +2255,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
pgoff_t index;
struct inode *inode = mapping->host;
handle_t *handle;
loff_t page_len;
index = pos >> PAGE_CACHE_SHIFT;
@ -2301,6 +2302,13 @@ retry:
*/
if (pos + len > inode->i_size)
ext4_truncate_failed_write(inode);
} else {
page_len = pos & (PAGE_CACHE_SIZE - 1);
if (page_len > 0) {
ret = ext4_discard_partial_page_buffers_no_lock(handle,
inode, page, pos - page_len, page_len,
EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED);
}
}
if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
@ -2343,6 +2351,7 @@ static int ext4_da_write_end(struct file *file,
loff_t new_i_size;
unsigned long start, end;
int write_mode = (int)(unsigned long)fsdata;
loff_t page_len;
if (write_mode == FALL_BACK_TO_NONDELALLOC) {
if (ext4_should_order_data(inode)) {
@ -2391,6 +2400,16 @@ static int ext4_da_write_end(struct file *file,
}
ret2 = generic_write_end(file, mapping, pos, len, copied,
page, fsdata);
page_len = PAGE_CACHE_SIZE -
((pos + copied - 1) & (PAGE_CACHE_SIZE - 1));
if (page_len > 0) {
ret = ext4_discard_partial_page_buffers_no_lock(handle,
inode, page, pos + copied - 1, page_len,
EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED);
}
copied = ret2;
if (ret2 < 0)
ret = ret2;