From: Alexander Viro Date: Thu, 23 Jun 2005 07:09:01 +0000 (-0700) Subject: [PATCH] fix for prune_icache()/forced final iput() races X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=991114c6fa6a21d1fa4d544abe78592352860c82;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git [PATCH] fix for prune_icache()/forced final iput() races Based on analysis and a patch from Russ Weight There is a race condition that can occur if an inode is allocated and then released (using iput) during the ->fill_super functions. The race condition is between kswapd and mount. For most filesystems this can only happen in an error path when kswapd is running concurrently. For isofs, however, the error can occur in a more common code path (which is how the bug was found). The logic here is "we want final iput() to free inode *now* instead of letting it sit in cache if fs is going down or had not quite come up". The problem is with kswapd seeing such inodes in the middle of being killed and happily taking over. The clean solution would be to tell kswapd to leave those inodes alone and let our final iput deal with them. I.e. add a new flag (I_FORCED_FREEING), set it before write_inode_now() there and make prune_icache() leave those alone. Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/inode.c b/fs/inode.c index 801fe7f3628..1f9a3a2b89b 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -500,7 +500,7 @@ repeat: continue; if (!test(inode, data)) continue; - if (inode->i_state & (I_FREEING|I_CLEAR)) { + if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE)) { __wait_on_freeing_inode(inode); goto repeat; } @@ -525,7 +525,7 @@ repeat: continue; if (inode->i_sb != sb) continue; - if (inode->i_state & (I_FREEING|I_CLEAR)) { + if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE)) { __wait_on_freeing_inode(inode); goto repeat; } @@ -727,7 +727,7 @@ EXPORT_SYMBOL(iunique); struct inode *igrab(struct inode *inode) { spin_lock(&inode_lock); - if (!(inode->i_state & I_FREEING)) + if (!(inode->i_state & (I_FREEING|I_WILL_FREE))) __iget(inode); else /* @@ -1024,17 +1024,21 @@ static void generic_forget_inode(struct inode *inode) if (!(inode->i_state & (I_DIRTY|I_LOCK))) list_move(&inode->i_list, &inode_unused); inodes_stat.nr_unused++; - spin_unlock(&inode_lock); - if (!sb || (sb->s_flags & MS_ACTIVE)) + if (!sb || (sb->s_flags & MS_ACTIVE)) { + spin_unlock(&inode_lock); return; + } + inode->i_state |= I_WILL_FREE; + spin_unlock(&inode_lock); write_inode_now(inode, 1); spin_lock(&inode_lock); + inode->i_state &= ~I_WILL_FREE; inodes_stat.nr_unused--; hlist_del_init(&inode->i_hash); } list_del_init(&inode->i_list); list_del_init(&inode->i_sb_list); - inode->i_state|=I_FREEING; + inode->i_state |= I_FREEING; inodes_stat.nr_inodes--; spin_unlock(&inode_lock); if (inode->i_data.nrpages) diff --git a/include/linux/fs.h b/include/linux/fs.h index e5a8db00df2..3622e952e98 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1025,6 +1025,7 @@ struct super_operations { #define I_FREEING 16 #define I_CLEAR 32 #define I_NEW 64 +#define I_WILL_FREE 128 #define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)