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fs: split out functions to hold writers
When a mount is marked read-only we set MNT_WRITE_HOLD on it if there aren't currently any active writers. Split this logic out into simple helpers that we can use in follow-up patches. Link: https://lore.kernel.org/r/20210121131959.646623-33-christian.brauner@ubuntu.com Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Suggested-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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1 changed files with 18 additions and 6 deletions
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@ -470,10 +470,8 @@ void mnt_drop_write_file(struct file *file)
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}
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}
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EXPORT_SYMBOL(mnt_drop_write_file);
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EXPORT_SYMBOL(mnt_drop_write_file);
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static int mnt_make_readonly(struct mount *mnt)
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static inline int mnt_hold_writers(struct mount *mnt)
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{
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{
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int ret = 0;
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mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
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mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
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/*
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/*
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* After storing MNT_WRITE_HOLD, we'll read the counters. This store
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* After storing MNT_WRITE_HOLD, we'll read the counters. This store
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@ -498,15 +496,29 @@ static int mnt_make_readonly(struct mount *mnt)
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* we're counting up here.
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* we're counting up here.
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*/
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*/
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if (mnt_get_writers(mnt) > 0)
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if (mnt_get_writers(mnt) > 0)
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ret = -EBUSY;
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return -EBUSY;
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else
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mnt->mnt.mnt_flags |= MNT_READONLY;
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return 0;
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}
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static inline void mnt_unhold_writers(struct mount *mnt)
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{
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/*
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/*
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* MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
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* MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
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* that become unheld will see MNT_READONLY.
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* that become unheld will see MNT_READONLY.
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*/
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*/
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smp_wmb();
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smp_wmb();
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mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
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mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
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}
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static int mnt_make_readonly(struct mount *mnt)
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{
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int ret;
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ret = mnt_hold_writers(mnt);
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if (!ret)
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mnt->mnt.mnt_flags |= MNT_READONLY;
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mnt_unhold_writers(mnt);
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return ret;
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return ret;
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}
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}
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