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From: Omar Sandoval <osandov@osandov.com>
To: linux-btrfs@vger.kernel.org
Cc: kernel-team@fb.com
Subject: [PATCH 1/5] Btrfs: use correct count in btrfs_file_write_iter()
Date: Thu, 15 Aug 2019 14:04:02 -0700
Message-ID: <06b24b06988a5fac5881a0eef613aa2ef0c63834.1565900769.git.osandov@fb.com> (raw)
In-Reply-To: <cover.1565900769.git.osandov@fb.com>

From: Omar Sandoval <osandov@fb.com>

generic_write_checks() may modify iov_iter_count(), so we must get the
count after the call, not before. Using the wrong one has a couple of
consequences:

1. We check a longer range in check_can_nocow() for nowait than we're
   actually writing.
2. We create extra hole extent maps in btrfs_cont_expand(). As far as I
   can tell, this is harmless, but I might be missing something.

These issues are pretty minor, but let's fix it before something more
important trips on it.

Fixes: edf064e7c6fe ("btrfs: nowait aio support")
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 fs/btrfs/file.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index b31991f0f440..4393b6b24e02 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1885,7 +1885,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
 	ssize_t err;
 	loff_t pos;
-	size_t count = iov_iter_count(from);
+	size_t count;
 	loff_t oldsize;
 	int clean_page = 0;
 
@@ -1906,6 +1906,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	}
 
 	pos = iocb->ki_pos;
+	count = iov_iter_count(from);
 	if (iocb->ki_flags & IOCB_NOWAIT) {
 		/*
 		 * We will allocate space in case nodatacow is not set,
-- 
2.17.1


  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-15 21:04 [RFC PATCH 0/5] Btrfs: add interface for writing compressed extent directly Omar Sandoval
2019-08-15 21:04 ` Omar Sandoval [this message]
2019-08-16 16:56   ` [PATCH 1/5] Btrfs: use correct count in btrfs_file_write_iter() Josef Bacik
2019-08-15 21:04 ` [PATCH 2/5] Btrfs: treat RWF_{,D}SYNC writes as sync for CRCs Omar Sandoval
2019-08-16 16:59   ` Josef Bacik
2019-08-27 12:35   ` David Sterba
2019-08-27 17:44     ` Omar Sandoval
2019-08-27 18:16       ` David Sterba
2019-08-15 21:04 ` [PATCH 3/5] Btrfs: stop clearing EXTENT_DIRTY in inode I/O tree Omar Sandoval
2019-08-16 16:59   ` Josef Bacik
2019-08-15 21:04 ` [RFC PATCH 4/5] fs: export rw_verify_area() Omar Sandoval
2019-08-16 17:02   ` Josef Bacik
2019-08-15 21:04 ` [RFC PATCH 5/5] Btrfs: add ioctl for directly writing compressed data Omar Sandoval
2019-08-26 21:36   ` Josef Bacik
2019-08-27  6:26     ` Nikolay Borisov
2019-08-27 11:57       ` Josef Bacik
2019-08-27 18:06         ` Omar Sandoval
2019-08-27 18:22           ` Omar Sandoval
2019-08-27 18:28             ` Josef Bacik
2019-08-28 12:06   ` David Sterba
2019-09-03 17:14     ` Omar Sandoval
2019-08-15 21:14 ` [RFC PATCH 0/5] Btrfs: add interface for writing compressed extent directly Omar Sandoval
2019-08-27 18:31 ` David Sterba

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