From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kamal Mostafa Subject: Re: [PATCH 10/19] ext4: Convert to new freezing mechanism Date: Wed, 07 Mar 2012 14:32:13 -0800 Message-ID: <1331159533.12984.73.camel@fourier> References: <1330963277-26336-1-git-send-email-jack@suse.cz> <1330963277-26336-11-git-send-email-jack@suse.cz> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-t26UvHsN9r+MA6GEJEvN" Cc: LKML , linux-fsdevel@vger.kernel.org, Al Viro , Christoph Hellwig , dchinner@redhat.com, sandeen@redhat.com, linux-ext4@vger.kernel.org, Theodore Ts'o To: Jan Kara Return-path: Received: from youngberry.canonical.com ([91.189.89.112]:49331 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932723Ab2CGWcZ (ORCPT ); Wed, 7 Mar 2012 17:32:25 -0500 In-Reply-To: <1330963277-26336-11-git-send-email-jack@suse.cz> Sender: linux-ext4-owner@vger.kernel.org List-ID: --=-t26UvHsN9r+MA6GEJEvN Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Re: the patch set: [PATCH 00/19] Fix filesystem freezing deadlocks In my initial smoke testing of this, I find that if I freeze a newly created ext4 filesystem immediately after mounting it for the very first time, then I get the new SB_FREEZE_COMPLETE warning from ext4_journal_start_sb() every 0.4 seconds from ext4lazyinit... # mkfs -t ext4 /dev/sdaX # mount /dev/sdaX /mnt # fsfreeze -f /mnt WARNING: at /home/kamal/src/linux/ubuntu-precise/fs/ext4/super.c:301 ext4_journal_start_sb+0x159/0x160() =20 Pid: 3252, comm: ext4lazyinit Tainted: G W 3.2.0-18-generic #28+kamal1+jankara1 =20 Call Trace: [] warn_slowpath_common+0x7f/0xc0 [] warn_slowpath_null+0x1a/0x20 [] ext4_journal_start_sb+0x159/0x160 [] ? ext4_init_inode_table+0xab/0x370 [] ext4_init_inode_table+0xab/0x370 [] ? schedule_timeout+0x175/0x320 [] ext4_run_li_request+0x85/0xe0 [] ext4_lazyinit_thread+0x9c/0x1c0 [] ? ext4_run_li_request+0xe0/0xe0 [] kthread+0x8c/0xa0 [] kernel_thread_helper+0x4/0x10 [] ? flush_kthread_worker+0xa0/0xa0 [] ? gs_change+0x13/0x13 -Kamal On Mon, 2012-03-05 at 17:01 +0100, Jan Kara wrote: > We remove most of frozen checks since upper layer takes care > of blocking all writes. We only have to handle protection in > ext4_page_mkwrite() in a special way because we cannot use > generic block_page_mkwrite(). >=20 > CC: linux-ext4@vger.kernel.org > CC: "Theodore Ts'o" > Signed-off-by: Jan Kara > --- > fs/ext4/inode.c | 7 ++----- > fs/ext4/super.c | 29 +++++------------------------ > 2 files changed, 7 insertions(+), 29 deletions(-) >=20 > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index feaa82f..c65baf9 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -4593,11 +4593,7 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, = struct vm_fault *vmf) > get_block_t *get_block; > int retries =3D 0; > =20 > - /* > - * This check is racy but catches the common case. We rely on > - * __block_page_mkwrite() to do a reliable check. > - */ > - vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); > + sb_start_pagefault(inode->i_sb); > /* Delalloc case is easy... */ > if (test_opt(inode->i_sb, DELALLOC) && > !ext4_should_journal_data(inode) && > @@ -4665,5 +4661,6 @@ retry_alloc: > out_ret: > ret =3D block_page_mkwrite_return(ret); > out: > + sb_end_pagefault(inode->i_sb); > return ret; > } > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 502c61f..0f1024a 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -289,33 +289,17 @@ static void ext4_put_nojournal(handle_t *handle) > * journal_end calls result in the superblock being marked dirty, so > * that sync() will call the filesystem's write_super callback if > * appropriate. > - * > - * To avoid j_barrier hold in userspace when a user calls freeze(), > - * ext4 prevents a new handle from being started by s_frozen, which > - * is in an upper layer. > */ > handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks) > { > journal_t *journal; > - handle_t *handle; > =20 > trace_ext4_journal_start(sb, nblocks, _RET_IP_); > if (sb->s_flags & MS_RDONLY) > return ERR_PTR(-EROFS); > =20 > + WARN_ON(sb->s_writers.frozen =3D=3D SB_FREEZE_COMPLETE); > journal =3D EXT4_SB(sb)->s_journal; > - handle =3D ext4_journal_current_handle(); > - > - /* > - * If a handle has been started, it should be allowed to > - * finish, otherwise deadlock could happen between freeze > - * and others(e.g. truncate) due to the restart of the > - * journal handle if the filesystem is forzen and active > - * handles are not stopped. > - */ > - if (!handle) > - vfs_check_frozen(sb, SB_FREEZE_TRANS); > - > if (!journal) > return ext4_get_nojournal(); > /* > @@ -4280,10 +4264,8 @@ int ext4_force_commit(struct super_block *sb) > return 0; > =20 > journal =3D EXT4_SB(sb)->s_journal; > - if (journal) { > - vfs_check_frozen(sb, SB_FREEZE_TRANS); > + if (journal) > ret =3D ext4_journal_force_commit(journal); > - } > =20 > return ret; > } > @@ -4315,9 +4297,8 @@ static int ext4_sync_fs(struct super_block *sb, int= wait) > * gives us a chance to flush the journal completely and mark the fs cle= an. > * > * Note that only this function cannot bring a filesystem to be in a cle= an > - * state independently, because ext4 prevents a new handle from being st= arted > - * by @sb->s_frozen, which stays in an upper layer. It thus needs help = from > - * the upper layer. > + * state independently. It relies on upper layer to stop all data & meta= data > + * modifications. > */ > static int ext4_freeze(struct super_block *sb) > { > @@ -4344,7 +4325,7 @@ static int ext4_freeze(struct super_block *sb) > EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER); > error =3D ext4_commit_super(sb, 1); > out: > - /* we rely on s_frozen to stop further updates */ > + /* we rely on upper layer to stop further updates */ > jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal); > return error; > } --=-t26UvHsN9r+MA6GEJEvN Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAABCAAGBQJPV+HtAAoJEHqwmdxYrXhZA4IP/0l5mIjXRP55+IgDI3jPK7fa OEth+VOAM0RUnf6W/Rzq1iPSp/vNyq6bE5FugfjKhK51xdjdIA9bnbT05VleBaWI lVGz/wMgq6GQa3DZW+pFa2lOy0mjLZNXNnYlC59J5i+RWPe9whd372+yPcRLLaLo 290xsg8c0Wa7MxUW4W84fCqMiusiwLV0M6FcghWqJDTt8/iDjh/P9FdDEXNyXa8M t7O9h/wL35JdFXGNKk+Gu5xTjksCi71WNzjWG8LNWX488UuR/iWczleTucZNb6cW Q1KqnnnrGZtTiiASaMp3eQRjSAmcNzbQD2Ipu4hRR1AEfXj1wDqdFtdC1hwwIG+l EOdXI4BFJCvCn4dPfHlgnCV+PnYsHhZ6qHfoBVEM1wyEh7ksBiaBjarP/g0EJpHi Bo0YQQLV96jANi0mZynJtrGtZbb5NmgxfHIxWQ4iwtCv5MHFAdKizEHVZ7DKVAhL 8uHNs/HMFgDQxi98b4p4Rj2WzUnR1o0nA0w2lFnlKN9J85+INz5P1ust/1Z6dp03 13sVD5Kmy1W4n4N7Zi1dhyTCT5gmpZLrYMYbzIP5o5sw9N5ettWmAjK7atT427yY nSqoYfBD1wAo2N0iHrEmC5f+H6/JlkNeoor6Dv/fqWG5mF8hyvOiPOXy0yPIvbIV PWjun4TSEtYz8jGyvhxq =o6lh -----END PGP SIGNATURE----- --=-t26UvHsN9r+MA6GEJEvN--