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 <aia21@cantab.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ntfs/logfile.c b/fs/ntfs/logfile.c
index acfed32..d7932e9 100644
--- a/fs/ntfs/logfile.c
+++ b/fs/ntfs/logfile.c
@@ -1,7 +1,7 @@
/*
* 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
@@ -724,24 +724,139 @@
*/
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 */