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| author | Christoph Hellwig <hch@infradead.org> | 2011-06-24 20:29:43 +0200 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2011-07-21 02:47:46 +0200 |
| commit | bd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3 (patch) | |
| tree | ef5341c7747f809aec7ae233f6e3ef90af39be5f /fs/ntfs | |
| parent | fs: simplify handling of zero sized reads in __blockdev_direct_IO (diff) | |
| download | linux-bd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3.tar.xz linux-bd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3.zip | |
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.c | 3 | ||||
| -rw-r--r-- | fs/ntfs/inode.c | 10 |
2 files changed, 3 insertions, 10 deletions
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c index f4b1057abdd2..b59f5ac26bef 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 c05d6dcf77a4..1371487da955 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) { |