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Fix lock ordering in fallocate

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We were seeing ABBA deadlocks on the dio_count wait and extent_sem
between fallocate and reads.  It turns out that fallocate got lock
ordering wrong.

This brings fallocate in line with the rest of the adherents to the lock
heirarchy.   Most importantly, the extent_sem is used after the
dio_count.   While we're at it we bring the i_mutex down to just before
the cluster lock for consistency.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2022-02-17 14:48:13 -08:00
parent 48966b42bb
commit 4d6350b3b0
1 changed files with 12 additions and 9 deletions
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kmod/src/data.c
+12 -9
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@@ -983,9 +983,6 @@ long scoutfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
u64 last;
s64 ret;
mutex_lock(&inode->i_mutex);
down_write(&si->extent_sem);
/* XXX support more flags */
if (mode & ~(FALLOC_FL_KEEP_SIZE)) {
ret = -EOPNOTSUPP;
@@ -1003,18 +1000,22 @@ long scoutfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
goto out;
}
mutex_lock(&inode->i_mutex);
ret = scoutfs_lock_inode(sb, SCOUTFS_LOCK_WRITE,
SCOUTFS_LKF_REFRESH_INODE, inode, &lock);
if (ret)
goto out;
goto out_mutex;
inode_dio_wait(inode);
down_write(&si->extent_sem);
if (!(mode & FALLOC_FL_KEEP_SIZE) &&
(offset + len > i_size_read(inode))) {
ret = inode_newsize_ok(inode, offset + len);
if (ret)
goto out;
goto out_extent;
}
iblock = offset >> SCOUTFS_BLOCK_SM_SHIFT;
@@ -1024,7 +1025,7 @@ long scoutfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
ret = scoutfs_inode_index_lock_hold(inode, &ind_locks, false, true);
if (ret)
goto out;
goto out_extent;
ret = fallocate_extents(sb, inode, iblock, last, lock);
@@ -1050,17 +1051,19 @@ long scoutfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
}
if (ret <= 0)
goto out;
goto out_extent;
iblock += ret;
ret = 0;
}
out:
scoutfs_unlock(sb, lock, SCOUTFS_LOCK_WRITE);
out_extent:
up_write(&si->extent_sem);
out_mutex:
scoutfs_unlock(sb, lock, SCOUTFS_LOCK_WRITE);
mutex_unlock(&inode->i_mutex);
out:
trace_scoutfs_data_fallocate(sb, ino, mode, offset, len, ret);
return ret;
}