NTFS: Fix a mount time deadlock.

Big thanks go to Mathias Kolehmainen for reporting the bug, providing
debug output and testing the patches I sent him to get it working.

The fix was to stop calling ntfs_attr_set() at mount time as that causes
balance_dirty_pages_ratelimited() to be called which on systems with
little memory actually tries to go and balance the dirty pages which tries
to take the s_umount semaphore but because we are still in fill_super()
across which the VFS holds s_umount for writing this results in a
deadlock.

We now do the dirty work by hand by submitting individual buffers. This
has the annoying "feature" that mounting can take a few seconds if the
journal is large as we have clear it all. One day someone should improve
on this by deferring the journal clearing to a helper kernel thread so it
can be done in the background but I don't have time for this at the moment
and the current solution works fine so I am leaving it like this for now.

Signed-off-by: Anton Altaparmakov <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/filesystems/ntfs.txt

···
 	device		/dev/hda5
 	raid-disk	0
 	device		/dev/hdb1
-	raid-disl	1
+	raid-disk	1
 
 For linear raid, just change the raid-level above to "raid-level linear", for
 mirrors, change it to "raid-level 1", and for stripe sets with parity, change
···
 
 Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog.
 
+2.1.29:
+	- Fix a deadlock when mounting read-write.
 2.1.28:
 	- Fix a deadlock.
 2.1.27:

fs/ntfs/ChangeLog

···
 	  happen is unclear however so it is worth waiting until someone hits
 	  the problem.
 
+2.1.29 - Fix a deadlock at mount time.
+
+	- During mount the VFS holds s_umount lock on the superblock.  So when
+	  we try to empty the journal $LogFile contents by calling
+	  ntfs_attr_set() when the machine does not have much memory and the
+	  journal is large ntfs_attr_set() results in the VM trying to balance
+	  dirty pages which in turn tries to that the s_umount lock and thus we
+	  get a deadlock.  The solution is to not use ntfs_attr_set() and
+	  instead do the zeroing by hand at the block level rather than page
+	  cache level.
+	- Fix sparse warnings.
+
 2.1.28 - Fix a deadlock.
 
 	- Fix deadlock in fs/ntfs/inode.c::ntfs_put_inode().  Thanks to Sergey

fs/ntfs/Makefile

···
 	     index.o inode.o mft.o mst.o namei.o runlist.o super.o sysctl.o \
 	     unistr.o upcase.o
 
-EXTRA_CFLAGS = -DNTFS_VERSION=\"2.1.28\"
+EXTRA_CFLAGS = -DNTFS_VERSION=\"2.1.29\"
 
 ifeq ($(CONFIG_NTFS_DEBUG),y)
 EXTRA_CFLAGS += -DDEBUG

fs/ntfs/aops.c

···
  * aops.c - NTFS kernel address space operations and page cache handling.
  *	    Part of the Linux-NTFS project.
  *
- * Copyright (c) 2001-2006 Anton Altaparmakov
+ * Copyright (c) 2001-2007 Anton Altaparmakov
  * Copyright (c) 2002 Richard Russon
  *
  * This program/include file is free software; you can redistribute it and/or
···
 	loff_t i_size;
 	struct inode *vi;
 	ntfs_inode *ni, *base_ni;
-	u8 *kaddr;
+	u8 *addr;
 	ntfs_attr_search_ctx *ctx;
 	MFT_RECORD *mrec;
 	unsigned long flags;
···
 		/* Race with shrinking truncate. */
 		attr_len = i_size;
 	}
-	kaddr = kmap_atomic(page, KM_USER0);
+	addr = kmap_atomic(page, KM_USER0);
 	/* Copy the data to the page. */
-	memcpy(kaddr, (u8*)ctx->attr +
+	memcpy(addr, (u8*)ctx->attr +
 			le16_to_cpu(ctx->attr->data.resident.value_offset),
 			attr_len);
 	/* Zero the remainder of the page. */
-	memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
+	memset(addr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
 	flush_dcache_page(page);
-	kunmap_atomic(kaddr, KM_USER0);
+	kunmap_atomic(addr, KM_USER0);
 put_unm_err_out:
 	ntfs_attr_put_search_ctx(ctx);
 unm_err_out:
···
 	loff_t i_size;
 	struct inode *vi = page->mapping->host;
 	ntfs_inode *base_ni = NULL, *ni = NTFS_I(vi);
-	char *kaddr;
+	char *addr;
 	ntfs_attr_search_ctx *ctx = NULL;
 	MFT_RECORD *m = NULL;
 	u32 attr_len;
···
 		/* Shrinking cannot fail. */
 		BUG_ON(err);
 	}
-	kaddr = kmap_atomic(page, KM_USER0);
+	addr = kmap_atomic(page, KM_USER0);
 	/* Copy the data from the page to the mft record. */
 	memcpy((u8*)ctx->attr +
 			le16_to_cpu(ctx->attr->data.resident.value_offset),
-			kaddr, attr_len);
+			addr, attr_len);
 	/* Zero out of bounds area in the page cache page. */
-	memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
-	kunmap_atomic(kaddr, KM_USER0);
+	memset(addr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
+	kunmap_atomic(addr, KM_USER0);
 	flush_dcache_page(page);
 	flush_dcache_mft_record_page(ctx->ntfs_ino);
 	/* We are done with the page. */

fs/ntfs/attrib.c

···
 /**
  * attrib.c - NTFS attribute operations.  Part of the Linux-NTFS project.
  *
- * Copyright (c) 2001-2006 Anton Altaparmakov
+ * Copyright (c) 2001-2007 Anton Altaparmakov
  * Copyright (c) 2002 Richard Russon
  *
  * This program/include file is free software; you can redistribute it and/or
···
 	struct page *page;
 	u8 *kaddr;
 	pgoff_t idx, end;
-	unsigned int start_ofs, end_ofs, size;
+	unsigned start_ofs, end_ofs, size;
 
 	ntfs_debug("Entering for ofs 0x%llx, cnt 0x%llx, val 0x%hx.",
 			(long long)ofs, (long long)cnt, val);
···
 		kunmap_atomic(kaddr, KM_USER0);
 		set_page_dirty(page);
 		page_cache_release(page);
+		balance_dirty_pages_ratelimited(mapping);
+		cond_resched();
 		if (idx == end)
 			goto done;
 		idx++;
···
 		kunmap_atomic(kaddr, KM_USER0);
 		set_page_dirty(page);
 		page_cache_release(page);
+		balance_dirty_pages_ratelimited(mapping);
+		cond_resched();
 	}
 done:
 	ntfs_debug("Done.");

fs/ntfs/file.c

···
 /*
  * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
  *
- * Copyright (c) 2001-2006 Anton Altaparmakov
+ * Copyright (c) 2001-2007 Anton Altaparmakov
  *
  * This program/include file is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as published
···
 #include <linux/swap.h>
 #include <linux/uio.h>
 #include <linux/writeback.h>
-#include <linux/sched.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
···
 	volatile char c;
 
 	/* Set @end to the first byte outside the last page we care about. */
-	end = (const char __user*)PAGE_ALIGN((ptrdiff_t __user)uaddr + bytes);
+	end = (const char __user*)PAGE_ALIGN((unsigned long)uaddr + bytes);
 
 	while (!__get_user(c, uaddr) && (uaddr += PAGE_SIZE, uaddr < end))
 		;
···
 	blocksize_bits = vol->sb->s_blocksize_bits;
 	u = 0;
 	do {
-		struct page *page = pages[u];
+		page = pages[u];
+		BUG_ON(!page);
 		/*
 		 * create_empty_buffers() will create uptodate/dirty buffers if
 		 * the page is uptodate/dirty.
···
 		size_t bytes)
 {
 	struct page **last_page = pages + nr_pages;
-	char *kaddr;
+	char *addr;
 	size_t total = 0;
 	unsigned len;
 	int left;
···
 		len = PAGE_CACHE_SIZE - ofs;
 		if (len > bytes)
 			len = bytes;
-		kaddr = kmap_atomic(*pages, KM_USER0);
-		left = __copy_from_user_inatomic(kaddr + ofs, buf, len);
-		kunmap_atomic(kaddr, KM_USER0);
+		addr = kmap_atomic(*pages, KM_USER0);
+		left = __copy_from_user_inatomic(addr + ofs, buf, len);
+		kunmap_atomic(addr, KM_USER0);
 		if (unlikely(left)) {
 			/* Do it the slow way. */
-			kaddr = kmap(*pages);
-			left = __copy_from_user(kaddr + ofs, buf, len);
+			addr = kmap(*pages);
+			left = __copy_from_user(addr + ofs, buf, len);
 			kunmap(*pages);
 			if (unlikely(left))
 				goto err_out;
···
 		size_t *iov_ofs, size_t bytes)
 {
 	struct page **last_page = pages + nr_pages;
-	char *kaddr;
+	char *addr;
 	size_t copied, len, total = 0;
 
 	do {
 		len = PAGE_CACHE_SIZE - ofs;
 		if (len > bytes)
 			len = bytes;
-		kaddr = kmap_atomic(*pages, KM_USER0);
-		copied = __ntfs_copy_from_user_iovec_inatomic(kaddr + ofs,
+		addr = kmap_atomic(*pages, KM_USER0);
+		copied = __ntfs_copy_from_user_iovec_inatomic(addr + ofs,
 				*iov, *iov_ofs, len);
-		kunmap_atomic(kaddr, KM_USER0);
+		kunmap_atomic(addr, KM_USER0);
 		if (unlikely(copied != len)) {
 			/* Do it the slow way. */
-			kaddr = kmap(*pages);
-			copied = __ntfs_copy_from_user_iovec_inatomic(kaddr + ofs,
+			addr = kmap(*pages);
+			copied = __ntfs_copy_from_user_iovec_inatomic(addr + ofs,
 					*iov, *iov_ofs, len);
 			/*
 			 * Zero the rest of the target like __copy_from_user().
 			 */
-			memset(kaddr + ofs + copied, 0, len - copied);
+			memset(addr + ofs + copied, 0, len - copied);
 			kunmap(*pages);
 			if (unlikely(copied != len))
 				goto err_out;
···
 	read_unlock_irqrestore(&ni->size_lock, flags);
 	BUG_ON(initialized_size != i_size);
 	if (end > initialized_size) {
-		unsigned long flags;
-
 		write_lock_irqsave(&ni->size_lock, flags);
 		ni->initialized_size = end;
 		i_size_write(vi, end);

fs/ntfs/inode.c

···
 #include "dir.h"
 #include "debug.h"
 #include "inode.h"
-#include "attrib.h"
 #include "lcnalloc.h"
 #include "malloc.h"
 #include "mft.h"
···
 	/* Resize the attribute record to best fit the new attribute size. */
 	if (new_size < vol->mft_record_size &&
 			!ntfs_resident_attr_value_resize(m, a, new_size)) {
-		unsigned long flags;
-
 		/* The resize succeeded! */
 		flush_dcache_mft_record_page(ctx->ntfs_ino);
 		mark_mft_record_dirty(ctx->ntfs_ino);

fs/ntfs/logfile.c

···
 /*
  * logfile.c - NTFS kernel journal handling. Part of the Linux-NTFS project.
  *
- * Copyright (c) 2002-2005 Anton Altaparmakov
+ * Copyright (c) 2002-2007 Anton Altaparmakov
  *
  * This program/include file is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as published
···
  */
 bool ntfs_empty_logfile(struct inode *log_vi)
 {
-	ntfs_volume *vol = NTFS_SB(log_vi->i_sb);
+	VCN vcn, end_vcn;
+	ntfs_inode *log_ni = NTFS_I(log_vi);
+	ntfs_volume *vol = log_ni->vol;
+	struct super_block *sb = vol->sb;
+	runlist_element *rl;
+	unsigned long flags;
+	unsigned block_size, block_size_bits;
+	int err;
+	bool should_wait = true;
 
 	ntfs_debug("Entering.");
-	if (!NVolLogFileEmpty(vol)) {
-		int err;
-		
-		err = ntfs_attr_set(NTFS_I(log_vi), 0, i_size_read(log_vi),
-				0xff);
-		if (unlikely(err)) {
-			ntfs_error(vol->sb, "Failed to fill $LogFile with "
-					"0xff bytes (error code %i).", err);
-			return false;
-		}
-		/* Set the flag so we do not have to do it again on remount. */
-		NVolSetLogFileEmpty(vol);
+	if (NVolLogFileEmpty(vol)) {
+		ntfs_debug("Done.");
+		return true;
 	}
+	/*
+	 * We cannot use ntfs_attr_set() because we may be still in the middle
+	 * of a mount operation.  Thus we do the emptying by hand by first
+	 * zapping the page cache pages for the $LogFile/$DATA attribute and
+	 * then emptying each of the buffers in each of the clusters specified
+	 * by the runlist by hand.
+	 */
+	block_size = sb->s_blocksize;
+	block_size_bits = sb->s_blocksize_bits;
+	vcn = 0;
+	read_lock_irqsave(&log_ni->size_lock, flags);
+	end_vcn = (log_ni->initialized_size + vol->cluster_size_mask) >>
+			vol->cluster_size_bits;
+	read_unlock_irqrestore(&log_ni->size_lock, flags);
+	truncate_inode_pages(log_vi->i_mapping, 0);
+	down_write(&log_ni->runlist.lock);
+	rl = log_ni->runlist.rl;
+	if (unlikely(!rl || vcn < rl->vcn || !rl->length)) {
+map_vcn:
+		err = ntfs_map_runlist_nolock(log_ni, vcn, NULL);
+		if (err) {
+			ntfs_error(sb, "Failed to map runlist fragment (error "
+					"%d).", -err);
+			goto err;
+		}
+		rl = log_ni->runlist.rl;
+		BUG_ON(!rl || vcn < rl->vcn || !rl->length);
+	}
+	/* Seek to the runlist element containing @vcn. */
+	while (rl->length && vcn >= rl[1].vcn)
+		rl++;
+	do {
+		LCN lcn;
+		sector_t block, end_block;
+		s64 len;
+
+		/*
+		 * If this run is not mapped map it now and start again as the
+		 * runlist will have been updated.
+		 */
+		lcn = rl->lcn;
+		if (unlikely(lcn == LCN_RL_NOT_MAPPED)) {
+			vcn = rl->vcn;
+			goto map_vcn;
+		}
+		/* If this run is not valid abort with an error. */
+		if (unlikely(!rl->length || lcn < LCN_HOLE))
+			goto rl_err;
+		/* Skip holes. */
+		if (lcn == LCN_HOLE)
+			continue;
+		block = lcn << vol->cluster_size_bits >> block_size_bits;
+		len = rl->length;
+		if (rl[1].vcn > end_vcn)
+			len = end_vcn - rl->vcn;
+		end_block = (lcn + len) << vol->cluster_size_bits >>
+				block_size_bits;
+		/* Iterate over the blocks in the run and empty them. */
+		do {
+			struct buffer_head *bh;
+
+			/* Obtain the buffer, possibly not uptodate. */
+			bh = sb_getblk(sb, block);
+			BUG_ON(!bh);
+			/* Setup buffer i/o submission. */
+			lock_buffer(bh);
+			bh->b_end_io = end_buffer_write_sync;
+			get_bh(bh);
+			/* Set the entire contents of the buffer to 0xff. */
+			memset(bh->b_data, -1, block_size);
+			if (!buffer_uptodate(bh))
+				set_buffer_uptodate(bh);
+			if (buffer_dirty(bh))
+				clear_buffer_dirty(bh);
+			/*
+			 * Submit the buffer and wait for i/o to complete but
+			 * only for the first buffer so we do not miss really
+			 * serious i/o errors.  Once the first buffer has
+			 * completed ignore errors afterwards as we can assume
+			 * that if one buffer worked all of them will work.
+			 */
+			submit_bh(WRITE, bh);
+			if (should_wait) {
+				should_wait = false;
+				wait_on_buffer(bh);
+				if (unlikely(!buffer_uptodate(bh)))
+					goto io_err;
+			}
+			brelse(bh);
+		} while (++block < end_block);
+	} while ((++rl)->vcn < end_vcn);
+	up_write(&log_ni->runlist.lock);
+	/*
+	 * Zap the pages again just in case any got instantiated whilst we were
+	 * emptying the blocks by hand.  FIXME: We may not have completed
+	 * writing to all the buffer heads yet so this may happen too early.
+	 * We really should use a kernel thread to do the emptying
+	 * asynchronously and then we can also set the volume dirty and output
+	 * an error message if emptying should fail.
+	 */
+	truncate_inode_pages(log_vi->i_mapping, 0);
+	/* Set the flag so we do not have to do it again on remount. */
+	NVolSetLogFileEmpty(vol);
 	ntfs_debug("Done.");
 	return true;
+io_err:
+	ntfs_error(sb, "Failed to write buffer.  Unmount and run chkdsk.");
+	goto dirty_err;
+rl_err:
+	ntfs_error(sb, "Runlist is corrupt.  Unmount and run chkdsk.");
+dirty_err:
+	NVolSetErrors(vol);
+	err = -EIO;
+err:
+	up_write(&log_ni->runlist.lock);
+	ntfs_error(sb, "Failed to fill $LogFile with 0xff bytes (error %d).",
+			-err);
+	return false;
 }
 
 #endif /* NTFS_RW */

fs/ntfs/runlist.c

···
 /**
  * runlist.c - NTFS runlist handling code.  Part of the Linux-NTFS project.
  *
- * Copyright (c) 2001-2005 Anton Altaparmakov
+ * Copyright (c) 2001-2007 Anton Altaparmakov
  * Copyright (c) 2002-2005 Richard Russon
  *
  * This program/include file is free software; you can redistribute it and/or
···
 					sizeof(*rl));
 		/* Adjust the beginning of the tail if necessary. */
 		if (end > rl->vcn) {
-			s64 delta = end - rl->vcn;
+			delta = end - rl->vcn;
 			rl->vcn = end;
 			rl->length -= delta;
 			/* Only adjust the lcn if it is real. */