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Commit d882962f authored by Matthew L. Creech's avatar Matthew L. Creech Committed by Artem Bityutskiy
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UBIFS: handle allocation failures in UBIFS write path 

Running kernel 2.6.37, my PPC-based device occasionally gets an
order-2 allocation failure in UBIFS, which causes the root FS to
become unwritable:

kswapd0: page allocation failure. order:2, mode:0x4050
Call Trace:
[c787dc30] [c00085b8] show_stack+0x7c/0x194 (unreliable)
[c787dc70] [c0061aec] __alloc_pages_nodemask+0x4f0/0x57c
[c787dd00] [c0061b98] __get_free_pages+0x20/0x50
[c787dd10] [c00e4f88] ubifs_jnl_write_data+0x54/0x200
[c787dd50] [c00e82d4] do_writepage+0x94/0x198
[c787dd90] [c00675e4] shrink_page_list+0x40c/0x77c
[c787de40] [c0067de0] shrink_inactive_list+0x1e0/0x370
[c787de90] [c0068224] shrink_zone+0x2b4/0x2b8
[c787df00] [c0068854] kswapd+0x408/0x5d4
[c787dfb0] [c0037bcc] kthread+0x80/0x84
[c787dff0] [c000ef44] kernel_thread+0x4c/0x68

Similar problems were encountered last April by Tomasz Stanislawski:

http://patchwork.ozlabs.org/patch/50965/



This patch implements Artem's suggested fix: fall back to a
mutex-protected static buffer, allocated at mount time.  I tested it
by forcing execution down the failure path, and didn't see any ill
effects.

Artem: massaged the patch a little, improved it so that we'd not
allocate the write reserve buffer when we are in R/O mode.

Signed-off-by: default avatarMatthew L. Creech <mlcreech@gmail.com>
Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
parent 2765df7d

fs/ubifs/journal.c

+22 −6
Original line number Diff line number Diff line
@@ -690,7 +690,7 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode, 
{

	struct ubifs_data_node *data;

	int err, lnum, offs, compr_type, out_len;

	int dlen = UBIFS_DATA_NODE_SZ + UBIFS_BLOCK_SIZE * WORST_COMPR_FACTOR;

	int dlen = COMPRESSED_DATA_NODE_BUF_SZ, allocated = 1;

	struct ubifs_inode *ui = ubifs_inode(inode);



	dbg_jnl("ino %lu, blk %u, len %d, key %s",
@@ -698,9 +698,19 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode, 
		DBGKEY(key));

	ubifs_assert(len <= UBIFS_BLOCK_SIZE);



	data = kmalloc(dlen, GFP_NOFS);

	if (!data)

		return -ENOMEM;

	data = kmalloc(dlen, GFP_NOFS | __GFP_NOWARN);

	if (!data) {

		/*

		 * Fall-back to the write reserve buffer. Note, we might be

		 * currently on the memory reclaim path, when the kernel is

		 * trying to free some memory by writing out dirty pages. The

		 * write reserve buffer helps us to guarantee that we are

		 * always able to write the data.

		 */

		allocated = 0;

		mutex_lock(&c->write_reserve_mutex);

		data = c->write_reserve_buf;

	}



	data->ch.node_type = UBIFS_DATA_NODE;

	key_write(c, key, &data->key);
@@ -736,6 +746,9 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode, 
		goto out_ro;



	finish_reservation(c);

	if (!allocated)

		mutex_unlock(&c->write_reserve_mutex);

	else

		kfree(data);

	return 0;
@@ -745,6 +758,9 @@ int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode, 
	ubifs_ro_mode(c, err);

	finish_reservation(c);

out_free:

	if (!allocated)

		mutex_unlock(&c->write_reserve_mutex);

	else

		kfree(data);

	return err;

}

fs/ubifs/super.c

+18 −0
Original line number Diff line number Diff line
@@ -1213,6 +1213,13 @@ static int mount_ubifs(struct ubifs_info *c) 
	if (c->bulk_read == 1)

		bu_init(c);



	if (!c->ro_mount) {

		c->write_reserve_buf = kmalloc(COMPRESSED_DATA_NODE_BUF_SZ,

					       GFP_KERNEL);

		if (!c->write_reserve_buf)

			goto out_free;

	}



	c->mounting = 1;



	err = ubifs_read_superblock(c);
@@ -1482,6 +1489,7 @@ static int mount_ubifs(struct ubifs_info *c) 
out_cbuf:

	kfree(c->cbuf);

out_free:

	kfree(c->write_reserve_buf);

	kfree(c->bu.buf);

	vfree(c->ileb_buf);

	vfree(c->sbuf);
@@ -1520,6 +1528,7 @@ static void ubifs_umount(struct ubifs_info *c) 
	kfree(c->cbuf);

	kfree(c->rcvrd_mst_node);

	kfree(c->mst_node);

	kfree(c->write_reserve_buf);

	kfree(c->bu.buf);

	vfree(c->ileb_buf);

	vfree(c->sbuf);
@@ -1605,6 +1614,10 @@ static int ubifs_remount_rw(struct ubifs_info *c) 
		goto out;

	}



	c->write_reserve_buf = kmalloc(COMPRESSED_DATA_NODE_BUF_SZ, GFP_KERNEL);

	if (!c->write_reserve_buf)

		goto out;



	err = ubifs_lpt_init(c, 0, 1);

	if (err)

		goto out;
@@ -1669,6 +1682,8 @@ static int ubifs_remount_rw(struct ubifs_info *c) 
		c->bgt = NULL;

	}

	free_wbufs(c);

	kfree(c->write_reserve_buf);

	c->write_reserve_buf = NULL;

	vfree(c->ileb_buf);

	c->ileb_buf = NULL;

	ubifs_lpt_free(c, 1);
@@ -1712,6 +1727,8 @@ static void ubifs_remount_ro(struct ubifs_info *c) 
	free_wbufs(c);

	vfree(c->orph_buf);

	c->orph_buf = NULL;

	kfree(c->write_reserve_buf);

	c->write_reserve_buf = NULL;

	vfree(c->ileb_buf);

	c->ileb_buf = NULL;

	ubifs_lpt_free(c, 1);
@@ -1942,6 +1959,7 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent) 
	mutex_init(&c->mst_mutex);

	mutex_init(&c->umount_mutex);

	mutex_init(&c->bu_mutex);

	mutex_init(&c->write_reserve_mutex);

	init_waitqueue_head(&c->cmt_wq);

	c->buds = RB_ROOT;

	c->old_idx = RB_ROOT;

fs/ubifs/ubifs.h

+14 −0
Original line number Diff line number Diff line
@@ -151,6 +151,12 @@ 
 */

#define WORST_COMPR_FACTOR 2



/*

 * How much memory is needed for a buffer where we comress a data node.

 */

#define COMPRESSED_DATA_NODE_BUF_SZ \

	(UBIFS_DATA_NODE_SZ + UBIFS_BLOCK_SIZE * WORST_COMPR_FACTOR)



/* Maximum expected tree height for use by bottom_up_buf */

#define BOTTOM_UP_HEIGHT 64
@@ -1005,6 +1011,11 @@ struct ubifs_debug_info; 
 * @bu_mutex: protects the pre-allocated bulk-read buffer and @c->bu

 * @bu: pre-allocated bulk-read information

 *

 * @write_reserve_mutex: protects @write_reserve_buf

 * @write_reserve_buf: on the write path we allocate memory, which might

 *                     sometimes be unavailable, in which case we use this

 *                     write reserve buffer

 *

 * @log_lebs: number of logical eraseblocks in the log

 * @log_bytes: log size in bytes

 * @log_last: last LEB of the log
@@ -1256,6 +1267,9 @@ struct ubifs_info { 
	struct mutex bu_mutex;

	struct bu_info bu;



	struct mutex write_reserve_mutex;

	void *write_reserve_buf;



	int log_lebs;

	long long log_bytes;

	int log_last;