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ext4: close race between direct IO and ext4_break_layouts()
If the refcount of a page is lowered between the time that it is returned by dax_busy_page() and when the refcount is again checked in ext4_break_layouts() => ___wait_var_event(), the waiting function ext4_wait_dax_page() will never be called. This means that ext4_break_layouts() will still have 'retry' set to false, so we'll stop looping and never check the refcount of other pages in this inode. Instead, always continue looping as long as dax_layout_busy_page() gives us a page which it found with an elevated refcount. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org
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commit
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1 changed files with 3 additions and 6 deletions
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@ -4195,9 +4195,8 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
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return 0;
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}
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static void ext4_wait_dax_page(struct ext4_inode_info *ei, bool *did_unlock)
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static void ext4_wait_dax_page(struct ext4_inode_info *ei)
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{
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*did_unlock = true;
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up_write(&ei->i_mmap_sem);
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schedule();
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down_write(&ei->i_mmap_sem);
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@ -4207,14 +4206,12 @@ int ext4_break_layouts(struct inode *inode)
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{
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struct ext4_inode_info *ei = EXT4_I(inode);
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struct page *page;
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bool retry;
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int error;
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if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem)))
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return -EINVAL;
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do {
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retry = false;
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page = dax_layout_busy_page(inode->i_mapping);
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if (!page)
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return 0;
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@ -4222,8 +4219,8 @@ int ext4_break_layouts(struct inode *inode)
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error = ___wait_var_event(&page->_refcount,
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atomic_read(&page->_refcount) == 1,
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TASK_INTERRUPTIBLE, 0, 0,
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ext4_wait_dax_page(ei, &retry));
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} while (error == 0 && retry);
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ext4_wait_dax_page(ei));
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} while (error == 0);
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return error;
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}
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