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From: Amir Goldstein <amir73il@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org
Subject: [PATCH 20/20] fanotify: no external fh buffer in fanotify_name_event
Date: Fri, 12 Jun 2020 12:33:43 +0300	[thread overview]
Message-ID: <20200612093343.5669-21-amir73il@gmail.com> (raw)
In-Reply-To: <20200612093343.5669-1-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 at
name_offset 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 | 72 ++++++++++++++++++++++++-----------
 fs/notify/fanotify/fanotify.h |  4 ++
 2 files changed, 53 insertions(+), 23 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 3a2d48edaddd..c3986fbb6801 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -281,10 +281,22 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 	return test_mask & user_mask;
 }
 
+static unsigned 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;
+}
+
 static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
-			       gfp_t gfp)
+			       unsigned int prealloc_fh_len, gfp_t gfp)
 {
-	int dwords, type, bytes = 0;
+	int dwords, bytes, type = 0;
 	char *ext_buf = NULL;
 	void *buf = fh->buf;
 	int err;
@@ -293,15 +305,21 @@ static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
 	if (!inode)
 		return;
 
-	dwords = 0;
+	/*
+	 * !gpf means preallocated variable size fh, but prealloc_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 (!gfp)
+		bytes = prealloc_fh_len;
+	else
+		bytes = fanotify_encode_fh_len(inode);
+	if (bytes < 4 || WARN_ON_ONCE(bytes % 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 && bytes > FANOTIFY_INLINE_FH_LEN) {
+		/* Treat failure to allocate fh as failure to encode fh */
 		err = -ENOMEM;
 		ext_buf = kmalloc(bytes, gfp);
 		if (!ext_buf)
@@ -311,17 +329,19 @@ static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
 		buf = ext_buf;
 	}
 
+	dwords = bytes >> 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 || bytes < (dwords << 2))
 		goto out_err;
 
 	fh->type = type;
-	fh->len = bytes;
-	if (fh->len > FANOTIFY_INLINE_FH_LEN)
-		fh->name_offset = FANOTIFY_INLINE_FH_LEN;
-	else
-		fh->name_offset = fh->len;
+	fh->len = dwords << 2;
+	/*
+	 * name_offset is set to preallocated fh len, even if actual fh len
+	 * is shorter.
+	 */
+	fh->name_offset = prealloc_fh_len;
 
 	return;
 
@@ -398,7 +418,7 @@ 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, 0, gfp);
 
 	return &ffe->fae;
 }
@@ -410,16 +430,26 @@ struct fanotify_event *fanotify_alloc_name_event(struct inode *id,
 {
 	struct fanotify_name_event *fne;
 	struct fanotify_fh *dfh;
+	unsigned int prealloc_fh_len = fanotify_encode_fh_len(id);
+	unsigned int size;
 
-	fne = kmalloc(sizeof(*fne) + file_name->len + 1, gfp);
+	size = sizeof(*fne) - FANOTIFY_INLINE_FH_LEN + prealloc_fh_len;
+	if (file_name)
+		size += file_name->len + 1;
+	fne = kmalloc(size, gfp);
 	if (!fne)
 		return NULL;
 
 	fne->fae.type = FANOTIFY_EVENT_TYPE_FID_NAME;
 	fne->fsid = *fsid;
 	dfh = &fne->dir_fh;
-	fanotify_encode_fh(dfh, id, gfp);
-	fanotify_fh_copy_name(dfh, file_name);
+	fanotify_encode_fh(dfh, id, prealloc_fh_len, 0);
+	if (file_name)
+		fanotify_fh_copy_name(dfh, file_name);
+
+	pr_debug("%s: ino=%lu size=%u prealloc_fh_len=%u dir_fh_len=%u name_len=%u name='%.*s'\n",
+		 __func__, id->i_ino, size, prealloc_fh_len, dfh->len,
+		 dfh->name_len, dfh->name_len, fanotify_fh_name(dfh));
 
 	return &fne->fae;
 }
@@ -634,11 +664,7 @@ 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);
-
-	if (fanotify_fh_has_ext_buf(&fne->dir_fh))
-		kfree(fanotify_fh_ext_buf(&fne->dir_fh));
-	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 8cb062eefd3e..7cbdac4be42f 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -43,6 +43,10 @@ static inline void fanotify_fh_init(struct fanotify_fh *fh)
 
 static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh)
 {
+	/* No external buffer in a variable size allocated fh */
+	if (fh->name_offset)
+		return false;
+
 	return fh->len > FANOTIFY_INLINE_FH_LEN;
 }
 
-- 
2.17.1


      parent reply	other threads:[~2020-06-12  9:34 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-12  9:33 [PATCH 00/20] Prep work for fanotify named events Amir Goldstein
2020-06-12  9:33 ` [PATCH 01/20] fsnotify: Rearrange fast path to minimise overhead when there is no watcher Amir Goldstein
2020-07-03 14:03   ` Jan Kara
2020-07-04  9:30     ` Amir Goldstein
2020-07-06 11:05       ` Jan Kara
2020-07-09 17:56         ` fsnotify: minimise overhead when there are no marks with ignore mask Amir Goldstein
2020-07-26 15:20           ` fsnotify: minimise overhead when there are no marks related to sb Amir Goldstein
2020-07-27  7:44             ` Jan Kara
2020-07-27 10:02               ` Amir Goldstein
2020-06-12  9:33 ` [PATCH 02/20] fsnotify: fold fsnotify() call into fsnotify_parent() Amir Goldstein
2020-06-12  9:33 ` [PATCH 03/20] fsnotify: return non const from fsnotify_data_inode() Amir Goldstein
2020-06-12  9:33 ` [PATCH 04/20] nfsd: use fsnotify_data_inode() to get the unlinked inode Amir Goldstein
2020-06-12 10:25   ` Amir Goldstein
2020-06-12  9:33 ` [PATCH 05/20] kernfs: do not call fsnotify() with name without a parent Amir Goldstein
2020-06-29 13:27   ` Tejun Heo
2020-06-29 16:11   ` Greg Kroah-Hartman
2020-06-12  9:33 ` [PATCH 06/20] inotify: do not use objectid when comparing events Amir Goldstein
2020-06-12  9:33 ` [PATCH 07/20] fanotify: create overflow event type Amir Goldstein
2020-06-12  9:33 ` [PATCH 08/20] fanotify: break up fanotify_alloc_event() Amir Goldstein
2020-06-12  9:33 ` [PATCH 09/20] fsnotify: pass dir argument to handle_event() callback Amir Goldstein
2020-07-03 14:49   ` Jan Kara
2020-06-12  9:33 ` [PATCH 10/20] fanotify: generalize the handling of extra event flags Amir Goldstein
2020-06-12  9:33 ` [PATCH 11/20] fanotify: generalize merge logic of events on dir Amir Goldstein
2020-06-12  9:33 ` [PATCH 12/20] fanotify: distinguish between fid encode error and null fid Amir Goldstein
2020-06-12  9:33 ` [PATCH 13/20] fanotify: generalize test for FAN_REPORT_FID Amir Goldstein
2020-06-12  9:33 ` [PATCH 14/20] fanotify: mask out special event flags from ignored mask Amir Goldstein
2020-06-12  9:33 ` [PATCH 15/20] fanotify: prepare for implicit event flags in mark mask Amir Goldstein
2020-06-12  9:33 ` [PATCH 16/20] fanotify: use FAN_EVENT_ON_CHILD as implicit flag on sb/mount/non-dir marks Amir Goldstein
2020-06-12  9:33 ` [PATCH 17/20] fanotify: remove event FAN_DIR_MODIFY Amir Goldstein
2020-06-12  9:33 ` [PATCH 18/20] fsnotify: add object type "child" to object type iterator Amir Goldstein
2020-06-12  9:33 ` [PATCH 19/20] fanotify: move event name into fanotify_fh Amir Goldstein
2020-07-03 16:02   ` Jan Kara
2020-07-06  8:21     ` Amir Goldstein
2020-07-06 15:24       ` Jan Kara
2020-06-12  9:33 ` Amir Goldstein [this message]

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