diff options
author | Christoph Hellwig <hch@infradead.org> | 2011-06-24 14:29:43 -0400 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2011-07-20 20:47:46 -0400 |
commit | bd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3 (patch) | |
tree | ef5341c7747f809aec7ae233f6e3ef90af39be5f /fs/ext2 | |
parent | f9b5570d7fdedff32a2e78102bfb54cd1b12b289 (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/ext2')
0 files changed, 0 insertions, 0 deletions