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author | Joel Becker <joel.becker@oracle.com> | 2010-07-01 15:13:31 -0700 |
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committer | Joel Becker <joel.becker@oracle.com> | 2010-07-08 13:25:35 -0700 |
commit | 5693486bad2bc2ac585a2c24f7e2f3964b478df9 (patch) | |
tree | 03d61d72c1b73bbf0b049bf0328f8e0c69f35a43 /fs/ocfs2/aops.c | |
parent | a4bfb4cf11fd2211b788af59dc8a8b4394bca227 (diff) | |
download | linux-5693486bad2bc2ac585a2c24f7e2f3964b478df9.tar.bz2 |
ocfs2: Zero the tail cluster when extending past i_size.
ocfs2's allocation unit is the cluster. This can be larger than a block
or even a memory page. This means that a file may have many blocks in
its last extent that are beyond the block containing i_size. There also
may be more unwritten extents after that.
When ocfs2 grows a file, it zeros the entire cluster in order to ensure
future i_size growth will see cleared blocks. Unfortunately,
block_write_full_page() drops the pages past i_size. This means that
ocfs2 is actually leaking garbage data into the tail end of that last
cluster. This is a bug.
We adjust ocfs2_write_begin_nolock() and ocfs2_extend_file() to detect
when a write or truncate is past i_size. They will use
ocfs2_zero_extend() to ensure the data is properly zeroed.
Older versions of ocfs2_zero_extend() simply zeroed every block between
i_size and the zeroing position. This presumes three things:
1) There is allocation for all of these blocks.
2) The extents are not unwritten.
3) The extents are not refcounted.
(1) and (2) hold true for non-sparse filesystems, which used to be the
only users of ocfs2_zero_extend(). (3) is another bug.
Since we're now using ocfs2_zero_extend() for sparse filesystems as
well, we teach ocfs2_zero_extend() to check every extent between
i_size and the zeroing position. If the extent is unwritten, it is
ignored. If it is refcounted, it is CoWed. Then it is zeroed.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Cc: stable@kernel.org
Diffstat (limited to 'fs/ocfs2/aops.c')
-rw-r--r-- | fs/ocfs2/aops.c | 42 |
1 files changed, 28 insertions, 14 deletions
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c index 9a5c931439bd..742893ea7390 100644 --- a/fs/ocfs2/aops.c +++ b/fs/ocfs2/aops.c @@ -196,15 +196,14 @@ int ocfs2_get_block(struct inode *inode, sector_t iblock, dump_stack(); goto bail; } - - past_eof = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode)); - mlog(0, "Inode %lu, past_eof = %llu\n", inode->i_ino, - (unsigned long long)past_eof); - - if (create && (iblock >= past_eof)) - set_buffer_new(bh_result); } + past_eof = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode)); + mlog(0, "Inode %lu, past_eof = %llu\n", inode->i_ino, + (unsigned long long)past_eof); + if (create && (iblock >= past_eof)) + set_buffer_new(bh_result); + bail: if (err < 0) err = -EIO; @@ -1590,21 +1589,20 @@ out: * write path can treat it as an non-allocating write, which has no * special case code for sparse/nonsparse files. */ -static int ocfs2_expand_nonsparse_inode(struct inode *inode, loff_t pos, - unsigned len, +static int ocfs2_expand_nonsparse_inode(struct inode *inode, + struct buffer_head *di_bh, + loff_t pos, unsigned len, struct ocfs2_write_ctxt *wc) { int ret; - struct ocfs2_super *osb = OCFS2_SB(inode->i_sb); loff_t newsize = pos + len; - if (ocfs2_sparse_alloc(osb)) - return 0; + BUG_ON(ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))); if (newsize <= i_size_read(inode)) return 0; - ret = ocfs2_extend_no_holes(inode, newsize, pos); + ret = ocfs2_extend_no_holes(inode, di_bh, newsize, pos); if (ret) mlog_errno(ret); @@ -1614,6 +1612,18 @@ static int ocfs2_expand_nonsparse_inode(struct inode *inode, loff_t pos, return ret; } +static int ocfs2_zero_tail(struct inode *inode, struct buffer_head *di_bh, + loff_t pos) +{ + int ret = 0; + + BUG_ON(!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))); + if (pos > i_size_read(inode)) + ret = ocfs2_zero_extend(inode, di_bh, pos); + + return ret; +} + int ocfs2_write_begin_nolock(struct address_space *mapping, loff_t pos, unsigned len, unsigned flags, struct page **pagep, void **fsdata, @@ -1649,7 +1659,11 @@ int ocfs2_write_begin_nolock(struct address_space *mapping, } } - ret = ocfs2_expand_nonsparse_inode(inode, pos, len, wc); + if (ocfs2_sparse_alloc(osb)) + ret = ocfs2_zero_tail(inode, di_bh, pos); + else + ret = ocfs2_expand_nonsparse_inode(inode, di_bh, pos, len, + wc); if (ret) { mlog_errno(ret); goto out; |