On Thu 08-12-11 10:04:35, Kamal Mostafa wrote: > From: Valerie Aurora <val@xxxxxxxxxxxxxxxxx> > > Use trylock in try_to_writeback_inodes_sb to avoid read-write > deadlocks that could be triggered by freeze. Christoph asked about what is the exact deadlock this patch tries to fix. I don't think you answered that. So can you elaborate please? Is it somehow connected with the fact that ext4 calls try_to_writeback_inodes_sb() with i_mutex held? Honza > BugLink: https://bugs.launchpad.net/bugs/897421 > Signed-off-by: Valerie Aurora <val@xxxxxxxxxxxxxxxxx> > Cc: Kamal Mostafa <kamal@xxxxxxxxxxxxx> > Tested-by: Peter M. Petrakis <peter.petrakis@xxxxxxxxxxxxx> > [kamal@xxxxxxxxxxxxx: patch restructure] > Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> > --- > fs/fs-writeback.c | 13 ++++++++----- > 1 files changed, 8 insertions(+), 5 deletions(-) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index ea89b3f..3a80f1b 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -1274,8 +1274,9 @@ EXPORT_SYMBOL(writeback_inodes_sb); > * try_to_writeback_inodes_sb - start writeback if none underway > * @sb: the superblock > * > - * Invoke writeback_inodes_sb if no writeback is currently underway. > - * Returns 1 if writeback was started, 0 if not. > + * Invoke writeback_inodes_sb if no writeback is currently underway > + * and no one else holds the s_umount lock. Returns 1 if writeback > + * was started, 0 if not. > */ > int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) > { > @@ -1288,15 +1289,17 @@ EXPORT_SYMBOL(try_to_writeback_inodes_sb); > * @sb: the superblock > * @nr: the number of pages to write > * > - * Invoke writeback_inodes_sb if no writeback is currently underway. > - * Returns 1 if writeback was started, 0 if not. > + * Invoke writeback_inodes_sb if no writeback is currently underway > + * and no one else holds the s_umount lock. Returns 1 if writeback > + * was started, 0 if not. > */ > int try_to_writeback_inodes_sb_nr(struct super_block *sb, > unsigned long nr, > enum wb_reason reason) > { > if (!writeback_in_progress(sb->s_bdi)) { > - down_read(&sb->s_umount); > + if (!down_read_trylock(&sb->s_umount)) > + return 0; > if (nr == 0) > writeback_inodes_sb(sb, reason); > else > -- > 1.7.5.4 > -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
