path: root/mm/filemap.c
diff options
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 /mm/filemap.c
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 'mm/filemap.c')
1 files changed, 0 insertions, 3 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index a8251a8d345..f820e600f1a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -78,9 +78,6 @@
* ->i_mutex (generic_file_buffered_write)
* ->mmap_sem (fault_in_pages_readable->do_page_fault)
- * ->i_mutex
- * ->i_alloc_sem (various)
- *
* inode_wb_list_lock
* sb_lock (fs/fs-writeback.c)
* ->mapping->tree_lock (__sync_single_inode)