Commit 2ed5724d authored Jun 12, 2013 by Theodore Ts'o

ext4: add cond_resched() to ext4_free_blocks() & ext4_mb_regular_allocator()



For a file systems with a very large number of block groups, if all of
the block group bitmaps are in memory and the file system is
relatively badly fragmented, it's possible ext4_mb_regular_allocator()
to take a long time trying to find a good match.  This is especially
true if the tuning parameter mb_max_to_scan has been sent to a very
large number.  So add a cond_resched() to avoid soft lockup warnings
and to provide better system responsiveness.

For ext4_free_blocks(), if we are deleting a large range of blocks,
and data=journal is enabled so that EXT4_FREE_BLOCKS_FORGET is passed,
the loop to call sb_find_get_block() and to call ext4_forget() can
take over 10-15 milliseocnds or more.  So it's better to add a
cond_resched() here a well.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

parent 20970ba6

fs/ext4/mballoc.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -2105,6 +2105,7 @@ repeat:
		group = ac->ac_g_ex.fe_group;

		for (i = 0; i < ngroups; group++, i++) {
		cond_resched();
		/*
		* Artificially restricted ngroups for non-extent
		* files makes group > ngroups possible on first loop.
		@@ -4612,10 +4613,11 @@ void ext4_free_blocks(handle_t handle, struct inode inode,
		BUG_ON(bh && (count > 1));

		for (i = 0; i < count; i++) {
		cond_resched();
		if (!bh)
		tbh = sb_find_get_block(inode->i_sb,
		block + i);
		if (unlikely(!tbh))
		if (!tbh)
		continue;
		ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
		inode, tbh, block + i);

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