Author: kib
Date: Sat Mar 23 22:41:48 2013
New Revision: 248667
URL: http://svnweb.freebsd.org/changeset/base/248667
Log:
MFC r247387:
Inode block must not be read or written while cg block buffer is owned.
Modified:
stable/9/sys/ufs/ffs/ffs_alloc.c
Directory Properties:
stable/9/sys/ (props changed)
Modified: stable/9/sys/ufs/ffs/ffs_alloc.c
==============================================================================
--- stable/9/sys/ufs/ffs/ffs_alloc.c Sat Mar 23 22:23:15 2013
(r248666)
+++ stable/9/sys/ufs/ffs/ffs_alloc.c Sat Mar 23 22:41:48 2013
(r248667)
@@ -1724,6 +1724,17 @@ fail:
return (0);
}
+static inline struct buf *
+getinobuf(struct inode *ip, u_int cg, u_int32_t cginoblk, int gbflags)
+{
+ struct fs *fs;
+
+ fs = ip->i_fs;
+ return (getblk(ip->i_devvp, fsbtodb(fs, ino_to_fsba(fs,
+ cg * fs->fs_ipg + cginoblk)), (int)fs->fs_bsize, 0, 0,
+ gbflags));
+}
+
/*
* Determine whether an inode can be allocated.
*
@@ -1748,9 +1759,11 @@ ffs_nodealloccg(ip, cg, ipref, mode, unu
u_int8_t *inosused;
struct ufs2_dinode *dp2;
int error, start, len, loc, map, i;
+ u_int32_t old_initediblk;
fs = ip->i_fs;
ump = ip->i_ump;
+check_nifree:
if (fs->fs_cs(fs, cg).cs_nifree == 0)
return (0);
UFS_UNLOCK(ump);
@@ -1762,13 +1775,13 @@ ffs_nodealloccg(ip, cg, ipref, mode, unu
return (0);
}
cgp = (struct cg *)bp->b_data;
+restart:
if (!cg_chkmagic(cgp) || cgp->cg_cs.cs_nifree == 0) {
brelse(bp);
UFS_LOCK(ump);
return (0);
}
bp->b_xflags |= BX_BKGRDWRITE;
- cgp->cg_old_time = cgp->cg_time = time_second;
inosused = cg_inosused(cgp);
if (ipref) {
ipref %= fs->fs_ipg;
@@ -1796,7 +1809,6 @@ ffs_nodealloccg(ip, cg, ipref, mode, unu
panic("ffs_nodealloccg: block not in map");
}
ipref = i * NBBY + ffs(map) - 1;
- cgp->cg_irotor = ipref;
gotit:
/*
* Check to see if we need to initialize more inodes.
@@ -1804,9 +1816,37 @@ gotit:
if (fs->fs_magic == FS_UFS2_MAGIC &&
ipref + INOPB(fs) > cgp->cg_initediblk &&
cgp->cg_initediblk < cgp->cg_niblk) {
- ibp = getblk(ip->i_devvp, fsbtodb(fs,
- ino_to_fsba(fs, cg * fs->fs_ipg + cgp->cg_initediblk)),
- (int)fs->fs_bsize, 0, 0, 0);
+ old_initediblk = cgp->cg_initediblk;
+
+ /*
+ * Free the cylinder group lock before writing the
+ * initialized inode block. Entering the
+ * babarrierwrite() with the cylinder group lock
+ * causes lock order violation between the lock and
+ * snaplk.
+ *
+ * Another thread can decide to initialize the same
+ * inode block, but whichever thread first gets the
+ * cylinder group lock after writing the newly
+ * allocated inode block will update it and the other
+ * will realize that it has lost and leave the
+ * cylinder group unchanged.
+ */
+ ibp = getinobuf(ip, cg, old_initediblk, GB_LOCK_NOWAIT);
+ brelse(bp);
+ if (ibp == NULL) {
+ /*
+ * The inode block buffer is already owned by
+ * another thread, which must initialize it.
+ * Wait on the buffer to allow another thread
+ * to finish the updates, with dropped cg
+ * buffer lock, then retry.
+ */
+ ibp = getinobuf(ip, cg, old_initediblk, 0);
+ brelse(ibp);
+ UFS_LOCK(ump);
+ goto check_nifree;
+ }
bzero(ibp->b_data, (int)fs->fs_bsize);
dp2 = (struct ufs2_dinode *)(ibp->b_data);
for (i = 0; i < INOPB(fs); i++) {
@@ -1823,8 +1863,29 @@ gotit:
* loading of newly created filesystems.
*/
babarrierwrite(ibp);
- cgp->cg_initediblk += INOPB(fs);
+
+ /*
+ * After the inode block is written, try to update the
+ * cg initediblk pointer. If another thread beat us
+ * to it, then leave it unchanged as the other thread
+ * has already set it correctly.
+ */
+ error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
+ (int)fs->fs_cgsize, NOCRED, &bp);
+ UFS_LOCK(ump);
+ ACTIVECLEAR(fs, cg);
+ UFS_UNLOCK(ump);
+ if (error != 0) {
+ brelse(bp);
+ return (error);
+ }
+ cgp = (struct cg *)bp->b_data;
+ if (cgp->cg_initediblk == old_initediblk)
+ cgp->cg_initediblk += INOPB(fs);
+ goto restart;
}
+ cgp->cg_old_time = cgp->cg_time = time_second;
+ cgp->cg_irotor = ipref;
UFS_LOCK(ump);
ACTIVECLEAR(fs, cg);
setbit(inosused, ipref);
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