3.16.65-rc1 review patch. If anyone has any objections, please let me know.
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From: Theodore Ts'o tytso@mit.edu
commit 2b08b1f12cd664dc7d5c84ead9ff25ae97ad5491 upstream.
The ext4_inline_data_fiemap() function calls fiemap_fill_next_extent() while still holding the xattr semaphore. This is not necessary and it triggers a circular lockdep warning. This is because fiemap_fill_next_extent() could trigger a page fault when it writes into page which triggers a page fault. If that page is mmaped from the inline file in question, this could very well result in a deadlock.
This problem can be reproduced using generic/519 with a file system configuration which has the inline_data feature enabled.
Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Ben Hutchings ben@decadent.org.uk --- fs/ext4/inline.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -1846,12 +1846,12 @@ int ext4_inline_data_fiemap(struct inode physical += (char *)ext4_raw_inode(&iloc) - iloc.bh->b_data; physical += offsetof(struct ext4_inode, i_block);
- if (physical) - error = fiemap_fill_next_extent(fieinfo, start, physical, - inline_len, flags); brelse(iloc.bh); out: up_read(&EXT4_I(inode)->xattr_sem); + if (physical) + error = fiemap_fill_next_extent(fieinfo, start, physical, + inline_len, flags); return (error < 0 ? error : 0); }