forked from Minki/linux
UBI: fix LEB locking
leb_read_unlock() may be called simultaniously by several tasks. The would race at the following code: up_read(&le->mutex); if (free) kfree(le); And it is possible that one task frees 'le' before the other tasks do 'up_read()'. Fix this by doing up_read and free inside the 'ubi->ltree' lock. Below it the oops we had because of this: BUG: spinlock bad magic on CPU#0, integck/7504 BUG: unable to handle kernel paging request at 6b6b6c4f IP: [<c0211221>] spin_bug+0x5c/0xdb *pde = 00000000 Oops: 0000 [#1] PREEMPT SMP Modules linked in: ubifs ubi nandsim nand nand_ids nand_ecc video output Pid: 7504, comm: integck Not tainted (2.6.26-rc3ubifs26 #8) EIP: 0060:[<c0211221>] EFLAGS: 00010002 CPU: 0 EIP is at spin_bug+0x5c/0xdb EAX: 00000032 EBX: 6b6b6b6b ECX: 6b6b6b6b EDX: f7f7ce30 ESI: f76491dc EDI: c044f51f EBP: e8a736cc ESP: e8a736a8 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 Process integck (pid: 7504, ti=e8a72000 task=f7f7ce30 task.ti=e8a72000) Stack: c044f754 c044f51f 00000000 f7f7d024 00001d50 00000001 f76491dc 00000296 f6df50e0 e8a736d8 c02112f0 f76491dc e8a736e8 c039157a f7d9e830 f76491d8 e8a7370c c020b975 f76491dc 00000296 f76491f8 00000000 f76491d8 00000000 Call Trace: [<c02112f0>] ? _raw_spin_unlock+0x50/0x7c [<c039157a>] ? _spin_unlock_irqrestore+0x20/0x58 [<c020b975>] ? rwsem_wake+0x4b/0x122 [<c0390e0a>] ? call_rwsem_wake+0xa/0xc [<c0139ee7>] ? up_read+0x28/0x31 [<f8873b3c>] ? leb_read_unlock+0x73/0x7b [ubi] [<f88742a3>] ? ubi_eba_read_leb+0x195/0x2b0 [ubi] [<f8872a04>] ? ubi_leb_read+0xaf/0xf8 [ubi] Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
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472018f73e
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23add7455c
@ -223,22 +223,18 @@ static int leb_read_lock(struct ubi_device *ubi, int vol_id, int lnum)
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*/
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static void leb_read_unlock(struct ubi_device *ubi, int vol_id, int lnum)
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{
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int free = 0;
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struct ubi_ltree_entry *le;
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spin_lock(&ubi->ltree_lock);
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le = ltree_lookup(ubi, vol_id, lnum);
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le->users -= 1;
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ubi_assert(le->users >= 0);
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up_read(&le->mutex);
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if (le->users == 0) {
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rb_erase(&le->rb, &ubi->ltree);
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free = 1;
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kfree(le);
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}
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spin_unlock(&ubi->ltree_lock);
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up_read(&le->mutex);
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if (free)
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kfree(le);
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}
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/**
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@ -274,7 +270,6 @@ static int leb_write_lock(struct ubi_device *ubi, int vol_id, int lnum)
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*/
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static int leb_write_trylock(struct ubi_device *ubi, int vol_id, int lnum)
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{
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int free;
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struct ubi_ltree_entry *le;
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le = ltree_add_entry(ubi, vol_id, lnum);
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@ -289,12 +284,9 @@ static int leb_write_trylock(struct ubi_device *ubi, int vol_id, int lnum)
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ubi_assert(le->users >= 0);
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if (le->users == 0) {
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rb_erase(&le->rb, &ubi->ltree);
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free = 1;
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} else
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free = 0;
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spin_unlock(&ubi->ltree_lock);
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if (free)
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kfree(le);
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}
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spin_unlock(&ubi->ltree_lock);
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return 1;
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}
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@ -307,24 +299,19 @@ static int leb_write_trylock(struct ubi_device *ubi, int vol_id, int lnum)
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*/
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static void leb_write_unlock(struct ubi_device *ubi, int vol_id, int lnum)
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{
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int free;
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struct ubi_ltree_entry *le;
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spin_lock(&ubi->ltree_lock);
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le = ltree_lookup(ubi, vol_id, lnum);
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le->users -= 1;
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ubi_assert(le->users >= 0);
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up_write(&le->mutex);
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if (le->users == 0) {
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rb_erase(&le->rb, &ubi->ltree);
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free = 1;
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} else
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free = 0;
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spin_unlock(&ubi->ltree_lock);
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up_write(&le->mutex);
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if (free)
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kfree(le);
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}
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spin_unlock(&ubi->ltree_lock);
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}
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/**
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* ubi_eba_unmap_leb - un-map logical eraseblock.
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