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From: Amir Goldstein <amir73il@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org
Subject: [PATCH v5 10/22] fanotify: no external fh buffer in fanotify_name_event
Date: Thu, 16 Jul 2020 11:42:18 +0300	[thread overview]
Message-ID: <20200716084230.30611-11-amir73il@gmail.com> (raw)
In-Reply-To: <20200716084230.30611-1-amir73il@gmail.com>

The fanotify_fh struct has an inline buffer of size 12 which is enough
to store the most common local filesystem file handles (e.g. ext4, xfs).
For file handles that do not fit in the inline buffer (e.g. btrfs), an
external buffer is allocated to store the file handle.

When allocating a variable size fanotify_name_event, there is no point
in allocating also an external fh buffer when file handle does not fit
in the inline buffer.

Check required size for encoding fh, preallocate an event buffer
sufficient to contain both file handle and name and store the name after
the file handle.

At this time, when not reporting name in event, we still allocate
the fixed size fanotify_fid_event and an external buffer for large
file handles, but fanotify_alloc_name_event() has already been prepared
to accept a NULL file_name.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.c | 75 ++++++++++++++++++++++++-----------
 fs/notify/fanotify/fanotify.h | 12 +++---
 2 files changed, 59 insertions(+), 28 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 31fd41e91575..c107974d6830 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -298,6 +298,24 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 	return test_mask & user_mask;
 }
 
+/*
+ * Check size needed to encode fanotify_fh.
+ *
+ * Return size of encoded fh without fanotify_fh header.
+ * Return 0 on failure to encode.
+ */
+static int fanotify_encode_fh_len(struct inode *inode)
+{
+	int dwords = 0;
+
+	if (!inode)
+		return 0;
+
+	exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
+
+	return dwords << 2;
+}
+
 /*
  * Encode fanotify_fh.
  *
@@ -305,49 +323,54 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
  * Return 0 on failure to encode.
  */
 static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
-			      gfp_t gfp)
+			      unsigned int fh_len, gfp_t gfp)
 {
-	int dwords, type, bytes = 0;
+	int dwords, type = 0;
 	char *ext_buf = NULL;
 	void *buf = fh->buf;
 	int err;
 
 	fh->type = FILEID_ROOT;
 	fh->len = 0;
+	fh->flags = 0;
 	if (!inode)
 		return 0;
 
-	dwords = 0;
+	/*
+	 * !gpf means preallocated variable size fh, but fh_len could
+	 * be zero in that case if encoding fh len failed.
+	 */
 	err = -ENOENT;
-	type = exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
-	if (!dwords)
+	if (fh_len < 4 || WARN_ON_ONCE(fh_len % 4))
 		goto out_err;
 
-	bytes = dwords << 2;
-	if (bytes > FANOTIFY_INLINE_FH_LEN) {
-		/* Treat failure to allocate fh as failure to allocate event */
+	/* No external buffer in a variable size allocated fh */
+	if (gfp && fh_len > FANOTIFY_INLINE_FH_LEN) {
+		/* Treat failure to allocate fh as failure to encode fh */
 		err = -ENOMEM;
-		ext_buf = kmalloc(bytes, gfp);
+		ext_buf = kmalloc(fh_len, gfp);
 		if (!ext_buf)
 			goto out_err;
 
 		*fanotify_fh_ext_buf_ptr(fh) = ext_buf;
 		buf = ext_buf;
+		fh->flags |= FANOTIFY_FH_FLAG_EXT_BUF;
 	}
 
+	dwords = fh_len >> 2;
 	type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
 	err = -EINVAL;
-	if (!type || type == FILEID_INVALID || bytes != dwords << 2)
+	if (!type || type == FILEID_INVALID || fh_len != dwords << 2)
 		goto out_err;
 
 	fh->type = type;
-	fh->len = bytes;
+	fh->len = fh_len;
 
-	return FANOTIFY_FH_HDR_LEN + bytes;
+	return FANOTIFY_FH_HDR_LEN + fh_len;
 
 out_err:
 	pr_warn_ratelimited("fanotify: failed to encode fid (type=%d, len=%d, err=%i)\n",
-			    type, bytes, err);
+			    type, fh_len, err);
 	kfree(ext_buf);
 	*fanotify_fh_ext_buf_ptr(fh) = NULL;
 	/* Report the event without a file identifier on encode error */
@@ -419,7 +442,8 @@ static struct fanotify_event *fanotify_alloc_fid_event(struct inode *id,
 
 	ffe->fae.type = FANOTIFY_EVENT_TYPE_FID;
 	ffe->fsid = *fsid;
-	fanotify_encode_fh(&ffe->object_fh, id, gfp);
+	fanotify_encode_fh(&ffe->object_fh, id, fanotify_encode_fh_len(id),
+			   gfp);
 
 	return &ffe->fae;
 }
@@ -432,8 +456,13 @@ static struct fanotify_event *fanotify_alloc_name_event(struct inode *id,
 	struct fanotify_name_event *fne;
 	struct fanotify_info *info;
 	struct fanotify_fh *dfh;
+	unsigned int dir_fh_len = fanotify_encode_fh_len(id);
+	unsigned int size;
 
-	fne = kmalloc(sizeof(*fne) + file_name->len + 1, gfp);
+	size = sizeof(*fne) + FANOTIFY_FH_HDR_LEN + dir_fh_len;
+	if (file_name)
+		size += file_name->len + 1;
+	fne = kmalloc(size, gfp);
 	if (!fne)
 		return NULL;
 
@@ -442,8 +471,13 @@ static struct fanotify_event *fanotify_alloc_name_event(struct inode *id,
 	info = &fne->info;
 	fanotify_info_init(info);
 	dfh = fanotify_info_dir_fh(info);
-	info->dir_fh_totlen = fanotify_encode_fh(dfh, id, gfp);
-	fanotify_info_copy_name(info, file_name);
+	info->dir_fh_totlen = fanotify_encode_fh(dfh, id, dir_fh_len, 0);
+	if (file_name)
+		fanotify_info_copy_name(info, file_name);
+
+	pr_debug("%s: ino=%lu size=%u dir_fh_len=%u name_len=%u name='%.*s'\n",
+		 __func__, id->i_ino, size, dir_fh_len,
+		 info->name_len, info->name_len, fanotify_info_name(info));
 
 	return &fne->fae;
 }
@@ -658,12 +692,7 @@ static void fanotify_free_fid_event(struct fanotify_event *event)
 
 static void fanotify_free_name_event(struct fanotify_event *event)
 {
-	struct fanotify_name_event *fne = FANOTIFY_NE(event);
-	struct fanotify_fh *dfh = fanotify_info_dir_fh(&fne->info);
-
-	if (fanotify_fh_has_ext_buf(dfh))
-		kfree(fanotify_fh_ext_buf(dfh));
-	kfree(fne);
+	kfree(FANOTIFY_NE(event));
 }
 
 static void fanotify_free_event(struct fsnotify_event *fsn_event)
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 5e104fc56abb..12c204b1489f 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -29,8 +29,10 @@ enum {
 struct fanotify_fh {
 	u8 type;
 	u8 len;
-	u8 pad[2];
-	unsigned char buf[FANOTIFY_INLINE_FH_LEN];
+#define FANOTIFY_FH_FLAG_EXT_BUF 1
+	u8 flags;
+	u8 pad;
+	unsigned char buf[];
 } __aligned(4);
 
 /* Variable size struct for dir file handle + child file handle + name */
@@ -50,7 +52,7 @@ struct fanotify_info {
 
 static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh)
 {
-	return fh->len > FANOTIFY_INLINE_FH_LEN;
+	return (fh->flags & FANOTIFY_FH_FLAG_EXT_BUF);
 }
 
 static inline char **fanotify_fh_ext_buf_ptr(struct fanotify_fh *fh)
@@ -154,6 +156,8 @@ struct fanotify_fid_event {
 	struct fanotify_event fae;
 	__kernel_fsid_t fsid;
 	struct fanotify_fh object_fh;
+	/* Reserve space in object_fh.buf[] - access with fanotify_fh_buf() */
+	unsigned char _inline_fh_buf[FANOTIFY_INLINE_FH_LEN];
 };
 
 static inline struct fanotify_fid_event *
@@ -166,8 +170,6 @@ struct fanotify_name_event {
 	struct fanotify_event fae;
 	__kernel_fsid_t fsid;
 	struct fanotify_info info;
-	/* Reserve space in info.buf[] - access with fanotify_info_dir_fh() */
-	struct fanotify_fh _dir_fh;
 };
 
 static inline struct fanotify_name_event *
-- 
2.17.1


  parent reply	other threads:[~2020-07-16  8:42 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-16  8:42 [PATCH v5 00/22] fanotify events with name info Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 01/22] fanotify: generalize the handling of extra event flags Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 02/22] fanotify: generalize merge logic of events on dir Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 03/22] fanotify: distinguish between fid encode error and null fid Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 04/22] fanotify: generalize test for FAN_REPORT_FID Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 05/22] fanotify: mask out special event flags from ignored mask Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 06/22] fanotify: prepare for implicit event flags in mark mask Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 07/22] fanotify: use FAN_EVENT_ON_CHILD as implicit flag on sb/mount/non-dir marks Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 08/22] fsnotify: add object type "child" to object type iterator Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 09/22] fanotify: use struct fanotify_info to parcel the variable size buffer Amir Goldstein
2020-07-16  8:42 ` Amir Goldstein [this message]
2020-07-16 12:44   ` [PATCH v5 10/22] fanotify: no external fh buffer in fanotify_name_event Jan Kara
2020-07-16 13:30     ` Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 11/22] dnotify: report both events on parent and child with single callback Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 12/22] inotify: " Amir Goldstein
2020-07-16 12:52   ` Jan Kara
2020-07-16 14:25     ` Amir Goldstein
2020-07-16 15:17       ` Jan Kara
2020-07-16  8:42 ` [PATCH v5 13/22] fanotify: " Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 14/22] fsnotify: send event to " Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 15/22] fsnotify: send event with parent/name info to sb/mount/non-dir marks Amir Goldstein
2020-07-16 17:01   ` Jan Kara
2020-07-16 17:20     ` Amir Goldstein
2020-07-16 17:57       ` Jan Kara
2020-07-16 18:42         ` Amir Goldstein
2020-07-16 22:34           ` Jan Kara
2020-07-17  3:49             ` Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 16/22] fsnotify: remove check that source dentry is positive Amir Goldstein
2020-07-16 13:13   ` Jan Kara
2020-07-16 13:29     ` Jan Kara
2020-07-16 13:54       ` Amir Goldstein
2020-07-16 14:06         ` Jan Kara
2020-07-16  8:42 ` [PATCH v5 17/22] fsnotify: send MOVE_SELF event with parent/name info Amir Goldstein
2020-07-16 13:45   ` Jan Kara
2020-07-16 13:59     ` Amir Goldstein
2020-07-16 14:10       ` Amir Goldstein
2020-07-16 15:57         ` Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 18/22] fanotify: add basic support for FAN_REPORT_DIR_FID Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 19/22] fanotify: report events with parent dir fid to sb/mount/non-dir marks Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 20/22] fanotify: add support for FAN_REPORT_NAME Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 21/22] fanotify: report parent fid + name + child fid Amir Goldstein
2020-07-16 15:59   ` Jan Kara
2020-07-16 16:08     ` Amir Goldstein
2020-07-16  8:42 ` [PATCH v5 22/22] fanotify: report parent fid " Amir Goldstein
2020-07-16 17:13 ` [PATCH v5 00/22] fanotify events with name info Jan Kara

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