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Tue, 4 Dec 2018 10:22:24 -0500 Received: from mx2.suse.de ([195.135.220.15]:33154 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726151AbeLDPWY (ORCPT ); Tue, 4 Dec 2018 10:22:24 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7BF72AF6E for ; Tue, 4 Dec 2018 15:22:20 +0000 (UTC) Subject: Re: [PATCH 2/2] btrfs: scrub: move scrub_setup_ctx allocation out of device_list_mutex To: David Sterba , linux-btrfs@vger.kernel.org Cc: fdmanana@suse.com References: From: Nikolay Borisov Openpgp: preference=signencrypt Autocrypt: addr=nborisov@suse.com; prefer-encrypt=mutual; keydata= xsFNBFiKBz4BEADNHZmqwhuN6EAzXj9SpPpH/nSSP8YgfwoOqwrP+JR4pIqRK0AWWeWCSwmZ T7g+RbfPFlmQp+EwFWOtABXlKC54zgSf+uulGwx5JAUFVUIRBmnHOYi/lUiE0yhpnb1KCA7f u/W+DkwGerXqhhe9TvQoGwgCKNfzFPZoM+gZrm+kWv03QLUCr210n4cwaCPJ0Nr9Z3c582xc bCUVbsjt7BN0CFa2BByulrx5xD9sDAYIqfLCcZetAqsTRGxM7LD0kh5WlKzOeAXj5r8DOrU2 GdZS33uKZI/kZJZVytSmZpswDsKhnGzRN1BANGP8sC+WD4eRXajOmNh2HL4P+meO1TlM3GLl EQd2shHFY0qjEo7wxKZI1RyZZ5AgJnSmehrPCyuIyVY210CbMaIKHUIsTqRgY5GaNME24w7h TyyVCy2qAM8fLJ4Vw5bycM/u5xfWm7gyTb9V1TkZ3o1MTrEsrcqFiRrBY94Rs0oQkZvunqia c+NprYSaOG1Cta14o94eMH271Kka/reEwSZkC7T+o9hZ4zi2CcLcY0DXj0qdId7vUKSJjEep c++s8ncFekh1MPhkOgNj8pk17OAESanmDwksmzh1j12lgA5lTFPrJeRNu6/isC2zyZhTwMWs k3LkcTa8ZXxh0RfWAqgx/ogKPk4ZxOXQEZetkEyTFghbRH2BIwARAQABzSJOaWtvbGF5IEJv cmlzb3YgPG5ib3Jpc292QHN1c2UuZGU+wsF4BBMBAgAiBQJYijkSAhsDBgsJCAcDAgYVCAIJ CgsEFgIDAQIeAQIXgAAKCRBxvoJG5T8oV/B6D/9a8EcRPdHg8uLEPywuJR8URwXzkofT5bZE IfGF0Z+Lt2ADe+nLOXrwKsamhweUFAvwEUxxnndovRLPOpWerTOAl47lxad08080jXnGfYFS Dc+ew7C3SFI4tFFHln8Y22Q9075saZ2yQS1ywJy+TFPADIprAZXnPbbbNbGtJLoq0LTiESnD w/SUC6sfikYwGRS94Dc9qO4nWyEvBK3Ql8NkoY0Sjky3B0vL572Gq0ytILDDGYuZVo4alUs8 LeXS5ukoZIw1QYXVstDJQnYjFxYgoQ5uGVi4t7FsFM/6ykYDzbIPNOx49Rbh9W4uKsLVhTzG BDTzdvX4ARl9La2kCQIjjWRg+XGuBM5rxT/NaTS78PXjhqWNYlGc5OhO0l8e5DIS2tXwYMDY LuHYNkkpMFksBslldvNttSNei7xr5VwjVqW4vASk2Aak5AleXZS+xIq2FADPS/XSgIaepyTV tkfnyreep1pk09cjfXY4A7qpEFwazCRZg9LLvYVc2M2eFQHDMtXsH59nOMstXx2OtNMcx5p8 0a5FHXE/HoXz3p9bD0uIUq6p04VYOHsMasHqHPbsMAq9V2OCytJQPWwe46bBjYZCOwG0+x58 fBFreP/NiJNeTQPOa6FoxLOLXMuVtpbcXIqKQDoEte9aMpoj9L24f60G4q+pL/54ql2VRscK d87BTQRYigc+ARAAyJSq9EFk28++SLfg791xOh28tLI6Yr8wwEOvM3wKeTfTZd+caVb9gBBy wxYhIopKlK1zq2YP7ZjTP1aPJGoWvcQZ8fVFdK/1nW+Z8/NTjaOx1mfrrtTGtFxVBdSCgqBB jHTnlDYV1R5plJqK+ggEP1a0mr/rpQ9dFGvgf/5jkVpRnH6BY0aYFPprRL8ZCcdv2DeeicOO YMobD5g7g/poQzHLLeT0+y1qiLIFefNABLN06Lf0GBZC5l8hCM3Rpb4ObyQ4B9PmL/KTn2FV Xq/c0scGMdXD2QeWLePC+yLMhf1fZby1vVJ59pXGq+o7XXfYA7xX0JsTUNxVPx/MgK8aLjYW hX+TRA4bCr4uYt/S3ThDRywSX6Hr1lyp4FJBwgyb8iv42it8KvoeOsHqVbuCIGRCXqGGiaeX Wa0M/oxN1vJjMSIEVzBAPi16tztL/wQtFHJtZAdCnuzFAz8ue6GzvsyBj97pzkBVacwp3/Mw qbiu7sDz7yB0d7J2tFBJYNpVt/Lce6nQhrvon0VqiWeMHxgtQ4k92Eja9u80JDaKnHDdjdwq FUikZirB28UiLPQV6PvCckgIiukmz/5ctAfKpyYRGfez+JbAGl6iCvHYt/wAZ7Oqe/3Cirs5 KhaXBcMmJR1qo8QH8eYZ+qhFE3bSPH446+5oEw8A9v5oonKV7zMAEQEAAcLBXwQYAQIACQUC WIoHPgIbDAAKCRBxvoJG5T8oV1pyD/4zdXdOL0lhkSIjJWGqz7Idvo0wjVHSSQCbOwZDWNTN JBTP0BUxHpPu/Z8gRNNP9/k6i63T4eL1xjy4umTwJaej1X15H8Hsh+zakADyWHadbjcUXCkg OJK4NsfqhMuaIYIHbToi9K5pAKnV953xTrK6oYVyd/Rmkmb+wgsbYQJ0Ur1Ficwhp6qU1CaJ mJwFjaWaVgUERoxcejL4ruds66LM9Z1Qqgoer62ZneID6ovmzpCWbi2sfbz98+kW46aA/w8r 7sulgs1KXWhBSv5aWqKU8C4twKjlV2XsztUUsyrjHFj91j31pnHRklBgXHTD/pSRsN0UvM26 lPs0g3ryVlG5wiZ9+JbI3sKMfbdfdOeLxtL25ujs443rw1s/PVghphoeadVAKMPINeRCgoJH zZV/2Z/myWPRWWl/79amy/9MfxffZqO9rfugRBORY0ywPHLDdo9Kmzoxoxp9w3uTrTLZaT9M KIuxEcV8wcVjr+Wr9zRl06waOCkgrQbTPp631hToxo+4rA1jiQF2M80HAet65ytBVR2pFGZF zGYYLqiG+mpUZ+FPjxk9kpkRYz61mTLSY7tuFljExfJWMGfgSg1OxfLV631jV1TcdUnx+h3l Sqs2vMhAVt14zT8mpIuu2VNxcontxgVr1kzYA/tQg32fVRbGr449j1gw57BV9i0vww== Message-ID: Date: Tue, 4 Dec 2018 17:22:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 4.12.18 г. 17:11 ч., David Sterba wrote: > The scrub context is allocated with GFP_KERNEL and called from > btrfs_scrub_dev under the fs_info::device_list_mutex. This is not safe > regarding reclaim that could try to flush filesystem data in order to > get the memory. And the device_list_mutex is held during superblock > commit, so this would cause a lockup. > > Move the alocation and initialization before any changes that require > the mutex. > > Signed-off-by: David Sterba > --- > fs/btrfs/scrub.c | 30 ++++++++++++++++++------------ > 1 file changed, 18 insertions(+), 12 deletions(-) > > diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c > index ffcab263e057..051d14c9f013 100644 > --- a/fs/btrfs/scrub.c > +++ b/fs/btrfs/scrub.c > @@ -3834,13 +3834,18 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, > return -EINVAL; > } > > + /* Allocate outside of device_list_mutex */ > + sctx = scrub_setup_ctx(fs_info, is_dev_replace); > + if (IS_ERR(sctx)) > + return PTR_ERR(sctx); > > mutex_lock(&fs_info->fs_devices->device_list_mutex); > dev = btrfs_find_device(fs_info, devid, NULL, NULL); > if (!dev || (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) && > !is_dev_replace)) { > mutex_unlock(&fs_info->fs_devices->device_list_mutex); > - return -ENODEV; > + ret = -ENODEV; > + goto out_free_ctx; > } > > if (!is_dev_replace && !readonly && > @@ -3848,7 +3853,8 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, > mutex_unlock(&fs_info->fs_devices->device_list_mutex); > btrfs_err_in_rcu(fs_info, "scrub: device %s is not writable", > rcu_str_deref(dev->name)); > - return -EROFS; > + ret = -EROFS; > + goto out_free_ctx; > } > > mutex_lock(&fs_info->scrub_lock); > @@ -3856,7 +3862,8 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, > test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &dev->dev_state)) { > mutex_unlock(&fs_info->scrub_lock); > mutex_unlock(&fs_info->fs_devices->device_list_mutex); > - return -EIO; > + ret = -EIO; > + goto out_free_ctx; > } > > btrfs_dev_replace_read_lock(&fs_info->dev_replace); > @@ -3866,7 +3873,8 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, > btrfs_dev_replace_read_unlock(&fs_info->dev_replace); > mutex_unlock(&fs_info->scrub_lock); > mutex_unlock(&fs_info->fs_devices->device_list_mutex); > - return -EINPROGRESS; > + ret = -EINPROGRESS; > + goto out_free_ctx; > } > btrfs_dev_replace_read_unlock(&fs_info->dev_replace); > > @@ -3874,16 +3882,9 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, > if (ret) { > mutex_unlock(&fs_info->scrub_lock); > mutex_unlock(&fs_info->fs_devices->device_list_mutex); > - return ret; > + goto out_free_ctx; Don't we suffer the same issue when calling scrub_workers_get since in it we do btrfs_alloc_workqueue which also calls kzalloc with GFP_KERNEL? > } > > - sctx = scrub_setup_ctx(fs_info, is_dev_replace); > - if (IS_ERR(sctx)) { > - mutex_unlock(&fs_info->scrub_lock); > - mutex_unlock(&fs_info->fs_devices->device_list_mutex); > - scrub_workers_put(fs_info); > - return PTR_ERR(sctx); > - } > sctx->readonly = readonly; > dev->scrub_ctx = sctx; > mutex_unlock(&fs_info->fs_devices->device_list_mutex); > @@ -3936,6 +3937,11 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, > > scrub_put_ctx(sctx); > > + return ret; > + > +out_free_ctx: > + scrub_free_ctx(sctx); > + > return ret; > } > >