Fix i_mutex vs. readdir handling in nfsd
Commit14f7dd63
("Copy XFS readdir hack into nfsd code") introduced a bug to generic code which had been extant for a long time in the XFS version -- it started to call through into lookup_one_len() and hence into the file systems' ->lookup() methods without i_mutex held on the directory. This patch fixes it by locking the directory's i_mutex again before calling the filldir functions. The original deadlocks which commit14f7dd63
was designed to avoid are still avoided, because they were due to fs-internal locking, not i_mutex. While we're at it, fix the return type of nfsd_buffered_readdir() which should be a __be32 not an int -- it's an NFS errno, not a Linux errno. And return nfserrno(-ENOMEM) when allocation fails, not just -ENOMEM. Sparse would have caught that, if it wasn't so busy bitching about __cold__. Commit05f4f678
("nfsd4: don't do lookup within readdir in recovery code") introduced a similar problem with calling lookup_one_len() without i_mutex, which this patch also addresses. To fix that, it was necessary to fix the called functions so that they expect i_mutex to be held; that part was done by J. Bruce Fields. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Umm-I-can-live-with-that-by: Al Viro <viro@zeniv.linux.org.uk> Reported-by: J. R. Okajima <hooanon05@yahoo.co.jp> Tested-by: J. Bruce Fields <bfields@citi.umich.edu> LKML-Reference: <8036.1237474444@jrobl> Cc: stable@kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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@@ -1890,8 +1890,8 @@ static int nfsd_buffered_filldir(void *__buf, const char *name, int namlen,
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return 0;
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}
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static int nfsd_buffered_readdir(struct file *file, filldir_t func,
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struct readdir_cd *cdp, loff_t *offsetp)
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static __be32 nfsd_buffered_readdir(struct file *file, filldir_t func,
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struct readdir_cd *cdp, loff_t *offsetp)
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{
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struct readdir_data buf;
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struct buffered_dirent *de;
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@@ -1901,11 +1901,12 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
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buf.dirent = (void *)__get_free_page(GFP_KERNEL);
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if (!buf.dirent)
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return -ENOMEM;
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return nfserrno(-ENOMEM);
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offset = *offsetp;
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while (1) {
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struct inode *dir_inode = file->f_path.dentry->d_inode;
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unsigned int reclen;
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cdp->err = nfserr_eof; /* will be cleared on successful read */
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@@ -1924,26 +1925,38 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
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if (!size)
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break;
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/*
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* Various filldir functions may end up calling back into
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* lookup_one_len() and the file system's ->lookup() method.
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* These expect i_mutex to be held, as it would within readdir.
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*/
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host_err = mutex_lock_killable(&dir_inode->i_mutex);
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if (host_err)
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break;
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de = (struct buffered_dirent *)buf.dirent;
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while (size > 0) {
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offset = de->offset;
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if (func(cdp, de->name, de->namlen, de->offset,
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de->ino, de->d_type))
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goto done;
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break;
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if (cdp->err != nfs_ok)
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goto done;
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break;
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reclen = ALIGN(sizeof(*de) + de->namlen,
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sizeof(u64));
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size -= reclen;
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de = (struct buffered_dirent *)((char *)de + reclen);
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}
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mutex_unlock(&dir_inode->i_mutex);
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if (size > 0) /* We bailed out early */
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break;
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offset = vfs_llseek(file, 0, SEEK_CUR);
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}
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done:
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free_page((unsigned long)(buf.dirent));
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if (host_err)
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