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authorChristoph Hellwig <hch@infradead.org>2011-06-24 14:29:43 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2011-07-20 20:47:46 -0400
commitbd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3 (patch)
treeef5341c7747f809aec7ae233f6e3ef90af39be5f /fs/ntfs
parentf9b5570d7fdedff32a2e78102bfb54cd1b12b289 (diff)
fs: kill i_alloc_sem
i_alloc_sem is a rather special rw_semaphore. It's the last one that may be released by a non-owner, and it's write side is always mirrored by real exclusion. It's intended use it to wait for all pending direct I/O requests to finish before starting a truncate. Replace it with a hand-grown construct: - exclusion for truncates is already guaranteed by i_mutex, so it can simply fall way - the reader side is replaced by an i_dio_count member in struct inode that counts the number of pending direct I/O requests. Truncate can't proceed as long as it's non-zero - when i_dio_count reaches non-zero we wake up a pending truncate using wake_up_bit on a new bit in i_flags - new references to i_dio_count can't appear while we are waiting for it to read zero because the direct I/O count always needs i_mutex (or an equivalent like XFS's i_iolock) for starting a new operation. This scheme is much simpler, and saves the space of a spinlock_t and a struct list_head in struct inode (typically 160 bits on a non-debug 64-bit system). Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/ntfs')
-rw-r--r--fs/ntfs/file.c3
-rw-r--r--fs/ntfs/inode.c10
2 files changed, 3 insertions, 10 deletions
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index f4b1057abdd..b59f5ac26be 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1832,9 +1832,8 @@ static ssize_t ntfs_file_buffered_write(struct kiocb *iocb,
* fails again.
*/
if (unlikely(NInoTruncateFailed(ni))) {
- down_write(&vi->i_alloc_sem);
+ inode_dio_wait(vi);
err = ntfs_truncate(vi);
- up_write(&vi->i_alloc_sem);
if (err || NInoTruncateFailed(ni)) {
if (!err)
err = -EIO;
diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index c05d6dcf77a..1371487da95 100644
--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -2357,12 +2357,7 @@ static const char *es = " Leaving inconsistent metadata. Unmount and run "
*
* Returns 0 on success or -errno on error.
*
- * Called with ->i_mutex held. In all but one case ->i_alloc_sem is held for
- * writing. The only case in the kernel where ->i_alloc_sem is not held is
- * mm/filemap.c::generic_file_buffered_write() where vmtruncate() is called
- * with the current i_size as the offset. The analogous place in NTFS is in
- * fs/ntfs/file.c::ntfs_file_buffered_write() where we call vmtruncate() again
- * without holding ->i_alloc_sem.
+ * Called with ->i_mutex held.
*/
int ntfs_truncate(struct inode *vi)
{
@@ -2887,8 +2882,7 @@ void ntfs_truncate_vfs(struct inode *vi) {
* We also abort all changes of user, group, and mode as we do not implement
* the NTFS ACLs yet.
*
- * Called with ->i_mutex held. For the ATTR_SIZE (i.e. ->truncate) case, also
- * called with ->i_alloc_sem held for writing.
+ * Called with ->i_mutex held.
*/
int ntfs_setattr(struct dentry *dentry, struct iattr *attr)
{