From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:33084 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754778AbeEaL3x (ORCPT ); Thu, 31 May 2018 07:29:53 -0400 From: Jeff Layton To: viro@ZenIV.linux.org.uk Cc: willy@infradead.org, andres@anarazel.de, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, cmaiolino@redhat.com Subject: [PATCH v2 5/5] vfs: add a new ioctl for fetching the superblock's errseq_t Date: Thu, 31 May 2018 07:29:45 -0400 Message-Id: <20180531112945.8629-6-jlayton@kernel.org> In-Reply-To: <20180531112945.8629-1-jlayton@kernel.org> References: <20180531112945.8629-1-jlayton@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: From: Jeff Layton The postgres developers recently mentioned that they'd like a way to tell whether there have been any writeback errors on a given filesystem without having to forcibly sync out all buffered writes. Now that we have a per-sb errseq_t that tracks whether any inode on the filesystem might have failed writeback, we can present that to userland applications via a new interface. Add a new generic fs ioctl for that purpose. This just reports the current state of the errseq_t counter with the SEEN bit masked off. Signed-off-by: Jeff Layton --- fs/ioctl.c | 3 +++ include/linux/errseq.h | 1 + include/uapi/linux/fs.h | 1 + lib/errseq.c | 33 +++++++++++++++++++++++++++++++-- 4 files changed, 36 insertions(+), 2 deletions(-) diff --git a/fs/ioctl.c b/fs/ioctl.c index 4823431d1c9d..fd5e6b7f395c 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -667,6 +667,9 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd, case FS_IOC_FIEMAP: return ioctl_fiemap(filp, arg); + case FS_IOC_GETFSERR: + return put_user(errseq_scrape(&inode->i_sb->s_wb_err), argp); + case FIGETBSZ: return put_user(inode->i_sb->s_blocksize, argp); diff --git a/include/linux/errseq.h b/include/linux/errseq.h index fc2777770768..de165623fa86 100644 --- a/include/linux/errseq.h +++ b/include/linux/errseq.h @@ -9,6 +9,7 @@ typedef u32 errseq_t; errseq_t errseq_set(errseq_t *eseq, int err); errseq_t errseq_sample(errseq_t *eseq); +errseq_t errseq_scrape(errseq_t *eseq); int errseq_check(errseq_t *eseq, errseq_t since); int errseq_check_and_advance(errseq_t *eseq, errseq_t *since); #endif diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index d2a8313fabd7..6dedb35c5a96 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -253,6 +253,7 @@ struct fsxattr { #define FS_IOC32_SETVERSION _IOW('v', 2, int) #define FS_IOC_FSGETXATTR _IOR ('X', 31, struct fsxattr) #define FS_IOC_FSSETXATTR _IOW ('X', 32, struct fsxattr) +#define FS_IOC_GETFSERR _IOR('e', 1, unsigned int) /* * File system encryption support diff --git a/lib/errseq.c b/lib/errseq.c index 81f9e33aa7e7..8ded0920eed3 100644 --- a/lib/errseq.c +++ b/lib/errseq.c @@ -108,7 +108,7 @@ errseq_t errseq_set(errseq_t *eseq, int err) EXPORT_SYMBOL(errseq_set); /** - * errseq_sample() - Grab current errseq_t value. + * errseq_sample() - Grab current errseq_t value (or 0 if it hasn't been seen) * @eseq: Pointer to errseq_t to be sampled. * * This function allows callers to initialise their errseq_t variable. @@ -117,7 +117,7 @@ EXPORT_SYMBOL(errseq_set); * see it the next time it checks for an error. * * Context: Any context. - * Return: The current errseq value. + * Return: The current errseq value or 0 if it wasn't previously seen */ errseq_t errseq_sample(errseq_t *eseq) { @@ -130,6 +130,35 @@ errseq_t errseq_sample(errseq_t *eseq) } EXPORT_SYMBOL(errseq_sample); +/** + * errseq_scrape() - Grab current errseq_t value + * @eseq: Pointer to errseq_t to be sampled. + * + * This function allows callers to scrape the current value of an errseq_t. + * Unlike errseq_sample, this will always return the current value with + * the SEEN flag unset, even when the value has not yet been seen. + * + * Context: Any context. + * Return: The current errseq value with ERRSEQ_SEEN masked off + */ +errseq_t errseq_scrape(errseq_t *eseq) +{ + errseq_t old = READ_ONCE(*eseq); + + /* + * For the common case of no errors ever having been set, we can skip + * marking the SEEN bit. Once an error has been set, the value will + * never go back to zero. + */ + if (old != 0) { + errseq_t new = old | ERRSEQ_SEEN; + if (old != new) + cmpxchg(eseq, old, new); + } + return old & ~ERRSEQ_SEEN; +} +EXPORT_SYMBOL(errseq_scrape); + /** * errseq_check() - Has an error occurred since a particular sample point? * @eseq: Pointer to errseq_t value to be checked. -- 2.17.0