There are two locks involved in managing the journal lists. The general reiserfs_write_lock and the journal->j_flush_mutex. While flush_journal_list is sleeping to acquire the j_flush_mutex or to submit a block for write, it will drop the write lock. This allows another thread to acquire the write lock and ultimately call flush_used_journal_lists to traverse the list of journal lists and select one for flushing. It can select the journal_list that has just had flush_journal_list called on it in the original thread and call it again with the same journal_list. The second thread then drops the write lock to acquire j_flush_mutex and the first thread reacquires it and continues execution and eventually clears and frees the journal list before dropping j_flush_mutex and returning. The second thread acquires j_flush_mutex and ends up operating on a journal_list that has already been released. If the memory hasn't been reused, we'll soon after hit a BUG_ON because the transaction id has already been cleared. If it's been reused, we'll crash in other fun ways. Since flush_journal_list will synchronize on j_flush_mutex, we can fix the race by taking a proper reference in flush_used_journal_lists and checking to see if it's still valid after the mutex is taken. It's safe to iterate the list of journal lists and pick a list with just the write lock as long as a reference is taken on the journal list before we drop the lock. We already have code to handle whether a transaction has been flushed already so we can use that to handle the race and get rid of the trans_id BUG_ON. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Jan Kara <jack@suse.cz>
Commit a3172027 introduced test_transaction as a requirement for flushing old lists -- but it can never return 1 unless the transaction has already been flushed. As a result, we have a routine that iterates the j_realblocks list but doesn't actually do anything. Since it's been this way since 2006 and the latency numbers were what Chris expected, let's just rip it out. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Jan Kara <jack@suse.cz>
Pull ext3, reiserfs, udf & isofs fixes from Jan Kara: "The contains a bunch of ext3 cleanups and minor improvements, major reiserfs locking changes which should hopefully fix deadlocks introduced by BKL removal, and udf/isofs changes to refuse mounting fs rw instead of mounting it ro automatically which makes eject button work as expected for all media (see the changelog for why userspace should be ok with this change)" * 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs: jbd: use a single printk for jbd_debug() reiserfs: locking, release lock around quota operations reiserfs: locking, handle nested locks properly reiserfs: locking, push write lock out of xattr code jbd: relocate assert after state lock in journal_commit_transaction() udf: Refuse RW mount of the filesystem instead of making it RO udf: Standardize return values in mount sequence isofs: Refuse RW mount of the filesystem instead of making it RO ext3: allow specifying external journal by pathname mount option jbd: remove unneeded semicolon
Previous commits released the write lock across quota operations but missed several places. In particular, the free operations can also call into the file system code and take the write lock, causing deadlocks. This patch introduces some more helpers and uses them for quota call sites. Without this patch applied, reiserfs + quotas runs into deadlocks under anything more than trivial load. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
The reiserfs write lock replaced the BKL and uses similar semantics. Frederic's locking code makes a distinction between when the lock is nested and when it's being acquired/released, but I don't think that's the right distinction to make. The right distinction is between the lock being released at end-of-use and the lock being released for a schedule. The unlock should return the depth and the lock should restore it, rather than the other way around as it is now. This patch implements that and adds a number of places where the lock should be dropped. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
The reiserfs xattr code doesn't need the write lock and sleeps all over the place. We can simplify the locking by releasing it and reacquiring after the xattr call. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Since remove_proc_entry() started to wait for IO in progress (i.e. since 2007 or so), the locking in fs/reiserfs/proc.c became wrong; if procfs read happens between the moment when umount() locks the victim superblock and removal of /proc/fs/reiserfs/<device>/*, we'll get a deadlock - read will wait for s_umount (in sget(), called by r_start()), while umount will wait in remove_proc_entry() for that read to finish, holding s_umount all along. Fortunately, the same change allows a much simpler race avoidance - all we need to do is remove the procfs entries in the very beginning of reiserfs ->kill_sb(); that'll guarantee that pointer to superblock will remain valid for the duration for procfs IO, so we don't need sget() to keep the sucker alive. As the matter of fact, we can get rid of the home-grown iterator completely, and use single_open() instead. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull ext4 update from Ted Ts'o: "Lots of bug fixes, cleanups and optimizations. In the bug fixes category, of note is a fix for on-line resizing file systems where the block size is smaller than the page size (i.e., file systems 1k blocks on x86, or more interestingly file systems with 4k blocks on Power or ia64 systems.) In the cleanup category, the ext4's punch hole implementation was significantly improved by Lukas Czerner, and now supports bigalloc file systems. In addition, Jan Kara significantly cleaned up the write submission code path. We also improved error checking and added a few sanity checks. In the optimizations category, two major optimizations deserve mention. The first is that ext4_writepages() is now used for nodelalloc and ext3 compatibility mode. This allows writes to be submitted much more efficiently as a single bio request, instead of being sent as individual 4k writes into the block layer (which then relied on the elevator code to coalesce the requests in the block queue). Secondly, the extent cache shrink mechanism, which was introduce in 3.9, no longer has a scalability bottleneck caused by the i_es_lru spinlock. Other optimizations include some changes to reduce CPU usage and to avoid issuing empty commits unnecessarily." * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (86 commits) ext4: optimize starting extent in ext4_ext_rm_leaf() jbd2: invalidate handle if jbd2_journal_restart() fails ext4: translate flag bits to strings in tracepoints ext4: fix up error handling for mpage_map_and_submit_extent() jbd2: fix theoretical race in jbd2__journal_restart ext4: only zero partial blocks in ext4_zero_partial_blocks() ext4: check error return from ext4_write_inline_data_end() ext4: delete unnecessary C statements ext3,ext4: don't mess with dir_file->f_pos in htree_dirblock_to_tree() jbd2: move superblock checksum calculation to jbd2_write_superblock() ext4: pass inode pointer instead of file pointer to punch hole ext4: improve free space calculation for inline_data ext4: reduce object size when !CONFIG_PRINTK ext4: improve extent cache shrink mechanism to avoid to burn CPU time ext4: implement error handling of ext4_mb_new_preallocation() ext4: fix corruption when online resizing a fs with 1K block size ext4: delete unused variables ext4: return FIEMAP_EXTENT_UNKNOWN for delalloc extents jbd2: remove debug dependency on debug_fs and update Kconfig help text jbd2: use a single printk for jbd_debug() ...
... and clean the callers up a bit Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
... and that - only to get the superblock. Privroot is a directory and we don't allow hardlinks to those... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>