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author | Christoph Hellwig <hch@infradead.org> | 2011-06-24 20:29:43 +0200 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2011-07-21 02:47:46 +0200 |
commit | bd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3 (patch) | |
tree | ef5341c7747f809aec7ae233f6e3ef90af39be5f /mm/truncate.c | |
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 'mm/truncate.c')
-rw-r--r-- | mm/truncate.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/truncate.c b/mm/truncate.c index e13f22efaad7..003c6c685fc8 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -622,12 +622,11 @@ int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end) return -ENOSYS; mutex_lock(&inode->i_mutex); - down_write(&inode->i_alloc_sem); + inode_dio_wait(inode); unmap_mapping_range(mapping, offset, (end - offset), 1); inode->i_op->truncate_range(inode, offset, end); /* unmap again to remove racily COWed private pages */ unmap_mapping_range(mapping, offset, (end - offset), 1); - up_write(&inode->i_alloc_sem); mutex_unlock(&inode->i_mutex); return 0; |