ext4: mark fc ineligible if inode gets evictied due to mem pressure

If inode gets evicted due to memory pressure, we have to remove it
from the fast commit list. However, that inode may have uncommitted
changes that fast commits will lose. So, just fall back to full
commits in this case. Also, rename the fast commit ineligiblity reason
from "EXT4_FC_REASON_MEM" to "EXT4_FC_REASON_MEM_NOMEM" for better
expression.
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201106035911.1942128-3-harshadshirwadkar@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/fast_commit.c

@@ -384,7 +384,7 @@ static int __track_dentry_update(struct inode *inode, void *arg, bool update)
 	mutex_unlock(&ei->i_fc_lock);
 	node = kmem_cache_alloc(ext4_fc_dentry_cachep, GFP_NOFS);
 	if (!node) {
-		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_MEM);
+		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_NOMEM);
 		mutex_lock(&ei->i_fc_lock);
 		return -ENOMEM;
 	}
@@ -397,7 +397,7 @@ static int __track_dentry_update(struct inode *inode, void *arg, bool update)
 		if (!node->fcd_name.name) {
 			kmem_cache_free(ext4_fc_dentry_cachep, node);
 			ext4_fc_mark_ineligible(inode->i_sb,
-				EXT4_FC_REASON_MEM);
+				EXT4_FC_REASON_NOMEM);
 			mutex_lock(&ei->i_fc_lock);
 			return -ENOMEM;
 		}

fs/ext4/fast_commit.h

@@ -100,7 +100,7 @@ enum {
 	EXT4_FC_REASON_XATTR = 0,
 	EXT4_FC_REASON_CROSS_RENAME,
 	EXT4_FC_REASON_JOURNAL_FLAG_CHANGE,
-	EXT4_FC_REASON_MEM,
+	EXT4_FC_REASON_NOMEM,
 	EXT4_FC_REASON_SWAP_BOOT,
 	EXT4_FC_REASON_RESIZE,
 	EXT4_FC_REASON_RENAME_DIR,

fs/ext4/inode.c

@@ -327,6 +327,8 @@ void ext4_evict_inode(struct inode *inode)
 	ext4_xattr_inode_array_free(ea_inode_array);
 	return;
 no_delete:
+	if (!list_empty(&EXT4_I(inode)->i_fc_list))
+		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_NOMEM);
 	ext4_clear_inode(inode);	/* We must guarantee clearing of inode... */
 }
 

include/trace/events/ext4.h

@@ -100,7 +100,7 @@ TRACE_DEFINE_ENUM(ES_REFERENCED_B);
 		{ EXT4_FC_REASON_XATTR,		"XATTR"},		\
 		{ EXT4_FC_REASON_CROSS_RENAME,	"CROSS_RENAME"},	\
 		{ EXT4_FC_REASON_JOURNAL_FLAG_CHANGE, "JOURNAL_FLAG_CHANGE"}, \
-		{ EXT4_FC_REASON_MEM,	"NO_MEM"},			\
+		{ EXT4_FC_REASON_NOMEM,	"NO_MEM"},			\
 		{ EXT4_FC_REASON_SWAP_BOOT,	"SWAP_BOOT"},		\
 		{ EXT4_FC_REASON_RESIZE,	"RESIZE"},		\
 		{ EXT4_FC_REASON_RENAME_DIR,	"RENAME_DIR"},		\
@@ -2917,13 +2917,13 @@ TRACE_EVENT(ext4_fc_stats,
 		    ),
 
 	    TP_printk("dev %d:%d fc ineligible reasons:\n"
-		      "%s:%d, %s:%d, %s:%d, %s:%d, %s:%d, %s:%d, %s:%d, %s,%d; "
+		      "%s:%d, %s:%d, %s:%d, %s:%d, %s:%d, %s:%d, %s:%d, %s:%d; "
 		      "num_commits:%ld, ineligible: %ld, numblks: %ld",
 		      MAJOR(__entry->dev), MINOR(__entry->dev),
 		      FC_REASON_NAME_STAT(EXT4_FC_REASON_XATTR),
 		      FC_REASON_NAME_STAT(EXT4_FC_REASON_CROSS_RENAME),
 		      FC_REASON_NAME_STAT(EXT4_FC_REASON_JOURNAL_FLAG_CHANGE),
-		      FC_REASON_NAME_STAT(EXT4_FC_REASON_MEM),
+		      FC_REASON_NAME_STAT(EXT4_FC_REASON_NOMEM),
 		      FC_REASON_NAME_STAT(EXT4_FC_REASON_SWAP_BOOT),
 		      FC_REASON_NAME_STAT(EXT4_FC_REASON_RESIZE),
 		      FC_REASON_NAME_STAT(EXT4_FC_REASON_RENAME_DIR),