WeiWei Wang
2015-May-11 06:42 UTC
[Ocfs2-devel] [PATCH] ocfs2: add ip_alloc_sem in direct IO to protect allocation changes
Hi all,
In ocfs2, ip_alloc_sem is used to protect allocation changes on the node.
In direct IO, we add ip_alloc_sem to protect date consistent between direct-io
and ocfs2_truncate_file race (buffer io use ip_alloc_sem already).
Although inode->i_mutex lock is used to avoid concurrency of above situation,
i think ip_alloc_sem is still needed because protect allocation changes is
significant.
Other filesystem like ext4 also uses rw_semaphore to protect data consistent
between get_block-vs-truncate race by other means, So ip_alloc_sem in ocfs2
direct io is needed.
Any comments are appreciated, thanks!
-- Weiwei Wang
Signed-off-by: Weiwei Wang <wangww631 at huawei.com>
---
fs/ocfs2/aops.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index f906a25..5b32450 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -533,10 +533,14 @@ static int ocfs2_direct_IO_get_blocks(struct inode *inode,
sector_t iblock,
inode_blocks = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
+ down_read(&OCFS2_I(inode)->ip_alloc_sem);
+
/* This figures out the size of the next contiguous block, and
* our logical offset */
ret = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno,
&contig_blocks, &ext_flags);
+ up_read(&OCFS2_I(inode)->ip_alloc_sem);
+
if (ret) {
mlog(ML_ERROR, "get_blocks() failed iblock=%llu\n",
(unsigned long long)iblock);
@@ -557,6 +561,8 @@ static int ocfs2_direct_IO_get_blocks(struct inode *inode,
sector_t iblock,
alloc_locked = 1;
+ down_write(&OCFS2_I(inode)->ip_alloc_sem);
+
/* fill hole, allocate blocks can't be larger than the size
* of the hole */
clusters_to_alloc = ocfs2_clusters_for_bytes(inode->i_sb, len);
@@ -567,6 +573,7 @@ static int ocfs2_direct_IO_get_blocks(struct inode *inode,
sector_t iblock,
ret = ocfs2_extend_allocation(inode, cpos,
clusters_to_alloc, 0);
if (ret < 0) {
+ up_write(&OCFS2_I(inode)->ip_alloc_sem);
mlog_errno(ret);
goto bail;
}
@@ -574,11 +581,13 @@ static int ocfs2_direct_IO_get_blocks(struct inode *inode,
sector_t iblock,
ret = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno,
&contig_blocks, &ext_flags);
if (ret < 0) {
+ up_write(&OCFS2_I(inode)->ip_alloc_sem);
mlog(ML_ERROR, "get_blocks() failed iblock=%llu\n",
(unsigned long long)iblock);
ret = -EIO;
goto bail;
}
+ up_write(&OCFS2_I(inode)->ip_alloc_sem);
}
/*
@@ -833,12 +842,17 @@ static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,
/* zeroing out the previously allocated cluster tail
* that but not zeroed */
- if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
+ if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
+ down_read(&OCFS2_I(inode)->ip_alloc_sem);
ret = ocfs2_direct_IO_zero_extend(osb, inode, offset,
zero_len_tail, cluster_align_tail);
- else
+ up_read(&OCFS2_I(inode)->ip_alloc_sem);
+ } else {
+ down_write(&OCFS2_I(inode)->ip_alloc_sem);
ret = ocfs2_direct_IO_extend_no_holes(osb, inode,
offset);
+ up_write(&OCFS2_I(inode)->ip_alloc_sem);
+ }
if (ret < 0) {
mlog_errno(ret);
ocfs2_inode_unlock(inode, 1);
--